JP5210756B2 - 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 end of the synthetic resin tube 3 can be expanded to be fitted and fitted , and the inner diameter is closer to the inner end in the radial direction at the tip, and the maximum diameter is natural. A synthetic resin joint body 1 including an inner cylinder portion 4 formed to have a substantially intermediate value between an inner diameter and an outer diameter of the tube 3 in a state and having a reverse taper angle, and a male screw portion 5, and ,
The internal thread portion 8 that can be screwed to the external thread portion 5 and the small diameter side portion of the expanded diameter changing region 9 in the expanded diameter portion 3A that is externally fitted to the inner cylinder portion 4 of the tube 3 can be used . Is a seal pressing portion 10 that is substantially equal to the outer diameter of the tube 3, a retaining pressing portion 11 that can act on the large-diameter side portion of the diameter expansion change region 9, and a constant diameter in the diameter expanding portion 3A. A union nut 2 made of a synthetic resin including a presser inner peripheral portion 13 that can be fitted onto the enlarged diameter straight portion 12 that is surrounded by the barrel portion 4B.
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 presser inner peripheral portion 13 is press-fitted to the diameter-enlarged straight portion 12 by screwing in the direction of the axial center P, and the large-diameter side portion of the diameter-enlargement changing region 9 is the retaining-use pressing portion. 11 and is pressed in the direction of the axis P, and the small diameter side portion of the diameter expansion change region 9 is set to be pressed in the direction of the axis P by the pressing portion 10 for sealing,
The presser inner peripheral part 13 has no radial gap between it and the enlarged diameter straight part 12, and the enlarged diameter part 3A is not rotated by tightening the union nut 2 so that the enlarged diameter part 3A is not rotated. It is characterized in that it is press-fitted to the diameter straight portion 12 .

According to a second aspect of the present invention, in the resin pipe joint according to the first aspect, the inner cylindrical portion 4 includes a tip tapered tube portion 4A for gradually expanding the diameter of the tube 3, and the tip tapered tube. The straight barrel portion 4B formed on the large diameter side of the portion 4A is formed, and the diameter-enlarged region 9 of the tube 3 is a portion that covers the tip portion cylindrical portion 4A. it is characterized in that.

The invention according to claim 3, in the resin pipe joint according to claim 2, wherein the straight barrel cylinder portion 4B is extended if to the opposite end to the distal end destination Subomari tube portion 4A of the inner cylinder portion 4 It is characterized by being.

According to a fourth aspect of the present invention, in the resin pipe joint according to the second aspect , the tip of the straight cylinder portion 4B is tapered in a state where the inner cylinder portion 4 is smaller in diameter than the straight cylinder portion 4B. It has a small diameter straight barrel portion 4C formed on the opposite side to the cylindrical portion 4A .

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. And the diameter-enlarging straight part fitted on the inner cylinder part is firmly held so as not to be inflated and deformed by being pressed against the outer peripheral surface of the straight barrel part and the inner periphery of the presser, and the retaining pressing part Is positioned so as to press the large-diameter side portion of the diameter-enlargement change region in the axial direction, so that the expansion deformation in the radial direction of the diameter-enlarged straight portion due to the pulling force is prevented, and the retaining Due to the synergy with the action of the pressing portion for suppressing the extraction movement of the enlarged diameter straight portion, a function of firmly restricting the movement of the enlarged diameter portion in the axial direction from the inner cylinder portion is generated. As a result, it is possible to provide a resin pipe joint 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.

According to the first aspect of the present invention, the union nut does not rotate with the enlarged diameter portion due to tightening, and does not cause inconveniences such as a shift of the seal point due to the rotational movement of the enlarged diameter portion and a decrease in the pull-out force resistance. However, there is an advantage that the diameter expansion straight portion can be firmly sandwiched and fixed between the straight barrel portion and the inner circumferential surface of the presser, and the pull-out force can be further improved.

According to the second aspect of the present invention, it is easy to perform external fitting on the inner cylinder part by expanding the tube diameter using the tapered part at the tip, and the effect of the pressing part for the seal on the diameter change region. will point to locations and the site of action of the enlarged diameter change region for retaining a pressing portion is apart axial directions, it is easy clearly to exhibit each of the sealing function and the retaining function, according to claim 1 There exists an advantage which can strengthen the said effect by invention.

According to the invention of claim 3 , since the inner tube portion is formed in a straight tube (straight tube) shape having a tapered tip portion, it is easy to perform mold forming, cutting processing, etc., and is excellent in productivity. There is.

According to the invention of claim 4 , since the inner tube portion is formed into a tapered tube shape having a tapered tip portion and a root narrowed portion, an advantage that the pull-out resistance of the tube becomes better. There is.

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 and 2 are cross-sectional views of the resin pipe joint according to the first embodiment and an enlarged cross-sectional view of the main part. FIGS. 3 and 4 are cross-sectional views of the resin pipe joint according to the second embodiment and an enlarged cross-section of the main part.

[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 is provided with an inner cylinder part 4 at one end that can be externally fitted by expanding the diameter of the end part of the tube 3, and continuously connected in a state of a larger diameter than the inner cylinder part 4. The outer peripheral male screw portion 5, the other end tapered male screw portion 6, and a cylindrical space-like fluid path 7 having an axis P are formed in a cylindrical member. The inner cylinder portion 4 includes a distal-end tapered tube portion 4A that gradually expands the diameter of the tube 3, a straight barrel portion 4B that is formed following the large-diameter side of the distal-end tapered tube portion 4A, and a straight barrel. A small diameter straight cylinder portion 4C, a straight cylinder portion 4B, and a small diameter straight cylinder portion 4C formed on the opposite side of the cylindrical portion 4A at the tip of the straight cylinder portion 4B in a state where the diameter is smaller than that of the portion 4B. And an expanded tubular portion 4D that is connected to the

The diameter of the portion where the male screw part 5 is formed is clearly larger than the straight cylinder part 4B having the maximum diameter of the inner cylinder part 4 as well as the small diameter straight cylinder part 4C. A side peripheral wall 15 perpendicular to the axis P is formed at the step portion of the boundary. 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. Note that the cut surface 16 is formed so that the maximum diameter is a substantially intermediate value between the inner diameter and the outer diameter of the tube 3 in the natural state .

  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. 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 large-diameter side end portion (an “large-diameter side portion”) The outer peripheral edge (an example of the retaining pressing portion) 11 that can act on the outer diameter straight portion 12 that is surrounded by the straight barrel portion 4B having a constant diameter in the larger diameter portion 3A. A presser inner peripheral portion 13 that can be fitted, and a guide cylinder portion 14 that surrounds the tube 3 over a predetermined length in the axial center P direction following the seal peripheral edge 10 are formed.

  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 circumferential edge 11 for retaining is larger in diameter than the outer peripheral surface 4b of the straight barrel portion 4B, which is the maximum diameter of the inner cylindrical portion 4, and the thickness of the tube 3 is added. Although it is set to a value smaller than the diameter, that is, the diameter of the presser inner peripheral portion 13, it may be different (for example, smaller than the outer peripheral surface 4 b). The pressing surface 11a of the retaining peripheral edge 11 is also a side peripheral surface orthogonal to the axis P.

  The presser inner peripheral portion 13 has no radial clearance between the presser inner peripheral portion 13 and the enlarged diameter straight portion 12 so that the enlarged diameter portion 3A is not rotated by tightening of the union nut 2. The retaining means N is configured to be set to a value that is press-fitted (press-fit externally fitted). This is because when the union nut 2 is tightened, the retaining peripheral edge 11 presses the enlarged diameter straight portion 12 in the axial direction so as to prevent the tube 3 from being pulled out. This is to prevent the portion 12 from escaping so as to swell outward in the radial direction, and to increase the pull-out force by cooperating with the peripheral edge 11 for retaining.

  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 is expanded by using a diameter expander (not shown) in advance, or the tube end is pushed into the inner cylinder portion 4 and then the tube end is moved to the side as shown in FIG. Insert until it contacts the peripheral wall 15. Then, the diameter-enlarged portion 3A that is the tube end is a diameter-enlarged change region 9 that is externally fitted to the outer peripheral surface 4a of the cylindrical portion 4A having a tapered tip, and an enlarged diameter that is externally fitted to the outer peripheral surface 4b of the straight barrel portion 4B. It is formed from a straight portion 12, a reduced diameter changing region 18 fitted on the outer peripheral surface 4d of the forwardly expanded cylindrical portion 4D, and a throttle straight portion 19 fitted on the outer peripheral surface 4c of the small diameter straight barrel portion 4C. Become.

  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 presser inner peripheral portion 13 is externally fitted to the enlarged diameter straight portion 12 by screwing in the direction of the axial center P, and the diameter is larger than the diameter of the inner cylinder portion 4 in the larger diameter side portion of the enlarged diameter changing region 9. Is set in such a manner that the peripheral edge 11 is pressed in the axial center P direction by the retaining peripheral edge 11 and the small diameter side portion of the expanded diameter change region 9 is pressed in the axial center P direction by the sealing peripheral edge 10. Yes. 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.

  In this case, as described above, there is no gap or almost no gap in the radial direction between the presser inner peripheral portion 13 and the enlarged diameter straight portion 12. Moreover, in Example 1, the diameter-expansion change area | region 9 of the tube 3 is formed as a part which the front-end | tip narrows and covers 4 A of cylinder parts. The diameter expansion change region 9 is a state of a taper tube that gradually expands, and the sealing peripheral edge 10 and the retaining peripheral edge 11 are in a positional relationship apart from each other in the axis P direction, but the tip tapered tube As the angle of the outer peripheral surface 4a of the portion 4A with respect to the axial center P becomes steeper, the distance in the axial center P direction between the sealing peripheral edge 10 and the retaining peripheral edge 11 becomes closer. Further, the sealing peripheral edge 10 and the inner cylinder portion 4 are slightly separated from each other in the direction of the axis P (see FIG. 2 and the like). However, if the angle of the outer peripheral surface 4a becomes steep, the distance is increased. If it becomes loose, the separation distance is reduced.

  As shown in FIGS. 1 and 2, in a predetermined assembled state of the resin pipe joint A, the sealing peripheral edge 10 has the small diameter side end portion of the diameter expansion change region 9 of the tube 3 in the axis P direction. Since the pressing is performed, the small diameter side end of the outer peripheral surface 4a of the diameter expansion change region 9 and the inner peripheral surface of the tube 3 in contact with the portion are strongly pressed to form the seal portion S. The tube 3 and the joint main body 1 are well sealed by the seal portion S at the tip of the inner tube portion 4 without any fluid such as cleaning liquid or chemical solution entering between the inner tube portion 4 and the enlarged diameter portion 3A. Yes.

  The diameter-enlarging straight part 12 of the diameter-enlarging part 3A that is press-fitted to the inner cylinder part 4 is surrounded by the outer peripheral surface 4b of the straight cylinder part 4B and the presser inner peripheral part 13, and first expands. It is held so that it cannot be deformed, and the circumferential edge 11 for retaining is positioned so as to substantially bite into the enlarged straight portion 12. This resists the pulling force acting on the enlarged diameter portion 3A due to the catch of the retaining peripheral edge 11 that pushes the large diameter side end portion of the enlarged diameter change region 9 so as to substantially bite into the enlarged diameter straight portion 12. In addition, the diameter-enlarging straight portion 12 can be expanded and deformed in the radial direction by the pulling force with the retaining peripheral edge 11 as a starting point. It also comes to be. If the diameter-enlarged portion 3A is displaced in the axial center P direction even a little, the seal point in the seal portion S may be shifted and the seal function may be uncertain, but this is prevented in advance. Therefore, the retaining means N in which the movement in the direction in which the diameter-enlarged portion 3A is pulled out from the inner cylinder portion 4 in the direction of the axis P is firmly restricted is configured, thereby realizing an excellent pull-out resistance. 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.

[Example 2]
As shown in FIGS. 3 and 4, the resin pipe joint A according to the second embodiment is the same as the resin pipe joint A according to the first embodiment except that the inner cylinder portion 4 has a straight shape. The description is made with the same reference numerals. The inner cylinder part 4 of the joint body 1 has a shape that does not have a constricted part composed of a tip-constricted cylinder part 4A and a straight cylinder part 4E. It consists of a change area 9 and an enlarged long straight portion 20.

  That is, the straight cylinder part 4B, the forward-bend cylinder part 4D, and the small-diameter straight cylinder part 4C in the joint body 1 of the first embodiment are replaced with the straight cylinder part 4E in the joint body 1 of the second embodiment. The enlarged diameter straight portion 12, the reduced diameter changing region 18, and the drawn straight portion 19 in the enlarged diameter portion 3A of Example 1 are replaced with an enlarged long straight portion 20 in the enlarged diameter portion 3A of Example 2. In other words, the straight tube portion 4E according to the second embodiment is such that the straight barrel portion 4B according to the first embodiment is extended to the end opposite to the tip portion of the inner tube portion 4 opposite to the tube portion 4A. The enlarged long straight portion 20 according to the second embodiment is obtained by extending the enlarged straight portion 12 according to the first embodiment to the side peripheral wall 15.

  When the resin pipe joints A according to Example 1 and Example 2 are compared with each other, in terms of resistance to pulling out of the tube 3, the one according to Example 1 having an inner cylinder portion 4 whose cross-sectional shape in the axial direction is a mountain shape. However, there is a disadvantage that the inner cylinder part 4 has a narrow diameter at the back and is difficult to process. In terms of ease of processing, the second embodiment having the inner tube portion 4 having a substantially straight shape in the axial direction of the cross section is long. Therefore, it is preferable to select and set appropriately in view of those advantages and disadvantages.

[Another Example]
In each retaining means N of the first and second embodiments, the diameter of the presser inner peripheral portion 13 is set so that there is no or almost no radial gap with the diameter-enlarging straight portion 12. Also good. Even in this configuration, when the union nut 2 is tightened, the retaining peripheral edge 11 presses the enlarged diameter straight portion 12 in the axial direction, thereby causing the enlarged diameter straight portion 12 to be deformed so as to bulge outward. The retaining means N is configured to restrict such that it hardly or hardly occurs, and an effective pulling-out force can be obtained.

  The sealing pressing portion 10 and the retaining pressing portion 11 are shown in FIG. 2 and the like, such as an intermittent circumferential edge divided into a plurality in the circumferential direction, and a cross-sectional shape with a corner angle of 80 degrees or 100 degrees. An angle other than 90 degrees (right angle) may be used. The outer peripheral surface 4b of the straight barrel portion 4B and the presser inner peripheral portion 13 are parallel to each other, but within a range in which bulging deformation to the outer diameter side of the diameter-enlarged straight portion 12 due to the pressing force of the retaining pressing portion 11 does not occur. If there is a relative angle, it may be slightly.

  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 constricted cylinder part 4B Straight cylinder part 4C Small diameter straight cylinder part 5 Male thread part 8 Female thread part 9 Expansion diameter change area 10 Sealing edge 11 Edge for retaining 12 Expanded straight section 13 Presser inner periphery P Shaft center

Claims (5)

The diameter of the end of the synthetic resin tube can be expanded and fitted externally , and the inner diameter in the radial direction is closer to the inner inner side, and the maximum diameter is a substantially intermediate value between the inner diameter and the outer diameter of the tube in a natural state. A synthetic resin joint body comprising an inner cylinder portion formed so as to have an angle of reverse taper and a male screw portion, and
It is possible to act on a small-diameter side portion of a diameter expansion change region in a female thread portion that can be screwed to the male thread portion and a diameter-enlarged portion that is externally fitted to the inner tube portion of the tube , and the inner diameter is the outer diameter of the tube A pressing portion for sealing that is substantially equal to the pressing portion, a pressing portion for retaining that can act on the large-diameter side portion of the diameter-enlargement change region, and a diameter-enlarging straight that is surrounded by a straight cylinder portion having a constant diameter in the diameter-enlarging portion A presser inner peripheral part that can be externally fitted to the part, and a union nut made of synthetic resin,
The union nut in the axial direction of the joint body of the union nut is formed by screwing the female threaded portion into the male threaded portion in a state where the tube is externally fitted to the inner cylindrical portion and the enlarged diameter portion is formed. By screwing, the presser inner peripheral portion is press-fitted to the diameter-enlarging straight portion, and the large-diameter side portion of the diameter-enlargement change region is pressed in the axial direction by the retaining pressing portion, and The small diameter side portion of the diameter expansion change region is set so as to be pressed in the axial direction by the sealing pressing portion,
The presser inner peripheral portion has no radial gap between it and the enlarged diameter straight portion, and the enlarged diameter straight portion does not cause rotation of the enlarged diameter portion due to tightening of the union nut. Resin pipe fitting that is press-fitted externally . The inner tube portion is formed to have a tip tapered tube portion that gradually expands the diameter of the tube, and the straight body tube portion that is formed on the large diameter side of the tip tapered tube portion. 2. The resin pipe joint according to claim 1 , wherein a diameter expansion change region of the tube is a portion that is constricted at the tip end and covers the cylindrical portion . 3. The resin pipe joint according to claim 2 , wherein the straight cylinder portion is extended to an end of the inner cylinder portion opposite to the tip tapered cylinder portion . The inner cylinder part has a small-diameter straight cylinder part formed on the opposite side of the front end tapered cylinder part of the straight cylinder part in a state in which the diameter is smaller than the straight cylinder part. 2. The resin pipe joint according to 2. 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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