JP5112216B2 - 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 diameter root portion 2a 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 cylinder 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 cylindrical portion 4 of the tube 3. 10 and a see-through synthetic resin union nut comprising a presser inner peripheral portion 13 that can be fitted onto the enlarged diameter straight portion 12 surrounded by the straight barrel portion 4B having a constant diameter in the enlarged diameter portion 3A. 2
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 axial center P direction, and the small-diameter side portion of the diameter-enlargement change region 9 is the seal-pressing portion 10. It is set to be pressed in the direction of the axis P,
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 press-fitted externally to the diameter straight part 12,
The union nut 2 is provided with a retaining pressing portion 11 that can act on the large-diameter side portion of the diameter-enlargement change region 9;
The retaining pressing portion 11 has a larger diameter than the outer peripheral surface 4b of the straight barrel portion 4B and is set to a diameter smaller than the diameter of the presser inner peripheral portion 13;
When the union nut 2 is screwed, the large-diameter side portion of the large-diameter changing region 9 is the retaining pressing portion 11 while the large-diameter straight portion 12 cannot escape and deform so as to bulge outward. It is set to be pressed in the direction of the heart P.

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 is the resin pipe joint according to claim 1 or 2, wherein the male screw portion 5 is also formed on the outer peripheral portion of the cover tube portion 6 .

According to a fourth aspect of the present invention, in the resin pipe joint according to any one of the first to third aspects, the straight body cylinder portion 4B is different from the tip tapered cylinder portion 4A of the inner cylinder portion 4. It is characterized by extending to the opposite end .

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 since the diameter-enlarging straight part fitted on the inner cylinder part is pressed against the outer peripheral surface of the straight cylinder part and the inner peripheral part of the presser foot, it can strongly resist the pulling force and is caused by the pulling force As a result, the diameter-expanded straight part is prevented from shifting in the axial direction by expanding and deforming in the radial direction due to the structure in which the diameter is expanded. As a result, the function of effectively restricting the movement in the direction of exiting from the inner cylinder portion is generated. In addition, it is possible to determine whether or not the end of the enlarged diameter portion that can be seen through the union nut is inward from the end of the cover tube portion, thereby determining whether or not the tube is correctly inserted into the inner tube portion. You can also do it. As a result, the joint body and the union nut are economical, and the function of the indicator means that shows the quality of the tube insertion through the union nut can be demonstrated, but the pull-out resistance It is possible to provide a resin pipe joint capable of achieving both good sealing performance and good sealing performance.

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 first aspect of the present invention, the diameter-enlarging straight portion that is externally fitted to the inner cylinder portion is brought into pressure contact with the outer peripheral surface of the straight barrel portion and the inner periphery of the presser, so that there is no escape place (expansion deformation or the like cannot be performed). ), Not only the pressing force is strengthened and firmly held, but also the retaining pressing part is positioned so as to press the large diameter side part of the diameter expansion changing region in the axial direction. Thus, the resin pipe joint can be provided in which the action of preventing movement in the direction of coming out of the inner cylinder portion in the axial direction is strengthened, and the pull-out resistance is 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. 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 exists an advantage which can strengthen the said effect by 2 invention.

According to the invention of claim 3, since the male screw portion and the insertion portion of the tube into the inner cylindrical portion can be made to overlap with each other in the axial direction, 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 4, 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, etc., and is excellent in productivity. 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. Further, if the joint body and the union nut are formed of the same fluororesin material, the linear expansion coefficients are also the same, and there is an advantage that the sealing performance at high temperature is improved.

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 the resin pipe joint of Example 1, FIG. 2 is an enlarged cross-sectional view of the main part of FIG. 1, FIG. 3 is an enlarged cross-sectional view showing the main part of the resin pipe joint of the reference example , and FIG. It is a result chart of a drawing power test. 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 main body 1 has an inner cylinder portion 4 at one end that can be fitted and expanded by expanding the end portion of the tube 3, and the outer peripheral side of the inner back side portion of the inner cylinder portion 4. A cover cylinder portion 6 having a circumferential groove (an example of a “radial gap”) m extending in the direction of the axis P to allow entry of the distal end of the tube 3 expanded in diameter, and a male screw portion comprising a trapezoidal screw 5 and a cylindrical space-like fluid path 7 having an axis P. 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. It is structured as a thing.

  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 outer peripheral surface that is the outer peripheral surface of the diameter is the inner peripheral surface 6a of the cover cylindrical portion 6. . 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.

  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 not be (for example, smaller than the outer peripheral surface 4 b), and acts on the large diameter side portion of the diameter expansion change region 9. Just do it. 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 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. It is inserted until it is in a state located inside the end wall 15 of the cover tube portion 6. 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 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 in the radial direction between the presser inner peripheral portion 13 and the enlarged diameter straight portion 12, and the enlarged diameter straight portion 12 is provided between the straight barrel portion 4B and the presser inner peripheral portion 13. It is in the state where it is clamped. Moreover, in Example 1, the diameter-expansion change area | region 9 of the tube 3 is formed as a part which tips the front-end | tip 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-enlarged 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.

  Moreover, as shown in FIGS. 1 and 2, the circumferential groove m formed by the inner back side of the inner cylinder part 4 and the cover cylinder part 6, and the union nut 2 formed by a fluororesin that can be seen through, An indicator means B that can visually check whether or not the tube 3 is correctly inserted into the inner cylinder portion 4 is configured. That is, the diameter-enlarged portion 3 </ b> A is visually observed on a line (see arrow A in FIG. 2) passing through the valley-like inner peripheral surface 22 on the inner back side of the presser inner peripheral portion 13 and reaching the female screw portion 8. If the tube 3 is in a normal state where the diameter-expanded end portion 3t is not visible, it can be determined that the tube 3 is correctly fitted on the inner cylinder portion 4. If the insertion failure state in which the enlarged diameter portion 3A can be seen and the enlarged diameter end portion 3t can be seen, or the insufficient diameter insertion portion in which the enlarged diameter portion 3A itself cannot be seen, the insertion of the tube 3 is still at the specified amount. In this case, an operation of further pushing the tube 3 is performed until the normal state is visible.

  In the indicator means B, the union nut 2 is formed using a transparent or translucent (milky white or the like) fluororesin so that an object inside thereof can be visually confirmed. The diameter of the union nut 2 is increased by seeing through a line passing through the valley-shaped inner peripheral surface 22 up to the female threaded portion 8 (see arrow A in FIG. 2). The part 3A is relatively clearly visible. On the other hand, the visibility of the enlarged diameter portion 3A is inferior at the part of the presser inner peripheral part 13 which is thicker than the part of the valley-shaped inner peripheral surface 22, and is difficult to see.

  And since the union nut 2 and the cover cylinder part 6 have overlapped in the part of the circumferential groove m in which the edge part of the tube 3 can enter, even if the joint main body 1 can also be seen through, thickness is a valley-shaped inner peripheral surface. In addition to being thicker than the portion 22, a change in the refractive index at the boundary surface due to the overlap between the male screw portion 5 and the female screw portion 8 is also added, so that it is impossible to visually recognize where the enlarged diameter end portion 3 t is located. . In addition, when the joint body 1 is not transparent such as being colored, it is needless to say that the enlarged diameter portion 3A or the enlarged diameter end portion 3t is seen on the inner and inner side of the end wall 15 of the cover cylinder portion 6. I can't.

  Therefore, the union nut 2 was tightened by the function of the indicator means B whether or not a normal state in which the enlarged diameter portion 3A can be seen from the valley-shaped inner peripheral surface 22 and the enlarged diameter end portion 3t cannot be seen. A resin pipe joint A that can be visually confirmed in a later assembled state and that is convenient and excellent in usability can be provided.

  In addition, the presence of the circumferential groove m and the cover tube portion 6 for constituting the indicator means B also provides an effect of functioning as an indicator when the tube 3 is inserted into the inner tube portion 4. That is, it can be confirmed whether or not the amount of insertion into the inner cylinder portion 4 by flaring the tube 3 is a predetermined amount. In other words, it is sufficient that the end portion 3t as the enlarged diameter portion 3A inserted into the inner cylinder portion 4 is located behind the end wall 15, and the quality can be visually determined when the tube 3 is assembled to the inner cylinder portion 4. As an advantage.

  Here, the fitting length to the inner cylinder part 4 in the axis P direction of the enlarged diameter part 3A is L (expanded fitting length L), and from the tip of the inner cylinder part 4 to the end wall 15 of the cover cylinder part 6 If the distance is D (minimum fitting length D) and the maximum tube fitting length of the circumferential groove m is d (adjustment fitting length d), the expanded fitting length L is the minimum fitting length D. It is only necessary to set the length to be equal to or less than the length obtained by adding the adjustment fitting length d to the minimum fitting length D, and this can be known by the indicator means B even after the union nut 2 is tightened. . That is, if D ≦ L ≦ (D + d), the amount of insertion of the tube 3 into the inner cylinder portion 4 is an appropriate amount.

  With the tube 3 inserted into the inner cylinder part 4 without acting the retaining edge 11, a test was conducted to determine how much force the tube 3 would pull out of the inner cylinder part 4 in the direction of the axis P. FIG. 4 shows the result obtained by using the tube 3 having a standard diameter. As an example of a standard diameter, when an inner diameter of 15.8 mm and an outer diameter of 19 mm are used, the pulling force is ○ when L = 5 mm, the pulling force is ◎ when L = 10 mm, and the pulling force is L = 15 mm. The result was that the force was ◎. Here, if the pull-out force is 80 kg or more, the determination is “good”, and if it is 90 kg or more, the determination is “good”. From this, if L is at least 10 mm, good pull-out resistance can be realized, so that L ≧ 10 mm is obtained. In this case, there is no upper limit for L, but if this is the case, the circumferential groove m becomes longer and the axial length of the pipe joint becomes larger.

  By the way, in order to cut the tube 3 with an appropriate length, a cutting tool is used to cut the tube 3 accurately. Usually, however, an ordinary worker usually cuts with a scissor. Often, the cut end is not exactly perpendicular to the tube axis but is cut obliquely. Since it is known from the data that the variation in the axial direction position of the cut surface due to the oblique cut is about 5 mm at the maximum, the substantial depth of the circumferential groove (length in the axial center P direction), that is, d = 5. L ≦ 15 mm as a result, and as a result, 10 mm ≦ Lmm ≦ 15 mm (D = 10 mm, D + d = 15 mm), the cut surface of the tube 3 is inclined, and the length in the axis P direction as a pipe joint is as much as possible. The tube 3 and the inner cylinder part 4 can be fitted in a state having a sufficient pull-out force while considering both of the restraining.

Therefore, the position of the expanded diameter end portion 3t in the axis P direction is OK as long as it is slightly behind the end wall 15 of the cover tube portion 6 as shown by the solid line in FIGS. The amount of insertion into the inner cylinder portion 4 is OK, and as shown by an imaginary line in FIG. 2, it may be inserted up to a position near the inner back end of the circumferential groove m. Of course, L <is a plug-shortage if D, there is no further to say to push the tube 3. The specific lengths of 10 mm and 15 mm mentioned above are only examples, and the actual values take into consideration various conditions such as the material, diameter, thickness, and amount of diameter expansion to the inner cylinder portion 4. It is determined appropriately.

[ Reference Example ]
As shown in FIG. 3, the resin pipe joint A according to the reference example is the same as the resin pipe joint A of Example 1 except that the union nut 2 in which the peripheral edge 11 for retaining is omitted is used. The same reference numerals are used for the explanation. That is, even enough to straight barrel cylinder portion 4B pressed to have a diameter straight portion 12 which is fitted in the peripheral portion 13 presser expansion nondeformable firmly held to, without stopping for circumferential edge 11 missing This structure is suitable for a case where a pull-out force is generated.

Since there is no contact between the peripheral edge 11 for retaining and the enlarged diameter portion 3A, there is an advantage that the tightening operation of the union nut 2 is lighter than that of the first embodiment. As indicated by phantom lines in FIG. 3, the inner peripheral portion of the union nut 2 between the sealing peripheral edge 10 and the presser inner peripheral portion 13 is close to the outer periphery of the tube in the diameter expansion change region 9. A resin pipe formed on the inclined inner peripheral surface 23 and devised so that the expanded diameter changing region 9 does not expand or deform outwardly by the pressing force of the sealing peripheral edge 10 to form the seal portion S. Joint A may be used.

[Another Example]
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. The inner diameter of the guide cylinder 14 may be equal to the inner diameter of the sealing peripheral edge 10.

  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. Expanded sectional view showing the main part of the resin pipe joint according to the reference example Chart showing the pull-out force test results from the inner tube of a standard tube

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 body cylinder part 5 Male thread part 6 Cover cylinder part 8 Female thread part 9 Expansion diameter change area 10 Sealing edge 11 Detent Edge 12 Expanded straight part 13 Presser inner periphery P Shaft center m Radial gap

Claims (5)

An inner tube portion that can be fitted and fitted by expanding the diameter of the end portion of the synthetic resin tube, and a cover tube portion that covers the inner tube portion with a radial gap that allows the tube to enter inside. And a synthetic resin joint body comprising 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 a small diameter side portion of the expanded diameter changing region of the expanded diameter portion that is externally fitted to the inner tube portion of the tube, and the expanded diameter portion A presser inner periphery that can be externally fitted to an enlarged straight portion surrounded by a straight cylindrical portion having a constant diameter, and a union nut made of a synthetic resin that can be seen through,
The union nut is screwed in the axial direction of the joint body by screwing the female threaded part into the male threaded part in a state where the tube is fitted on the inner cylinder part to form the enlarged diameter part. As a result, the inner circumferential portion of the presser is press-fitted and fitted to the enlarged diameter straight portion, and the small diameter side portion of the enlarged diameter changing region is set to be pressed in the axial direction by the sealing pressing portion. And
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. Press-fit externally,
The union nut is provided with a retaining pressing portion that can act on the large-diameter side portion of the diameter-change region,
The retaining pressing portion has a larger diameter than the outer peripheral surface of the straight barrel portion, and is set to a diameter smaller than the diameter of the presser inner peripheral portion,
When the union nut is screwed, the large-diameter side portion of the large-diameter change region is the retaining pressing portion in the axial direction in a state where the large-diameter straight portion does not escape and deform so as to bulge outward. Resin pipe joint set to be pressed.
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 . The resin pipe joint according to claim 1 or 2, wherein the male screw portion is also formed on an outer peripheral portion of the cover tube portion . The resin pipe joint according to any one of claims 1 to 3, wherein the straight barrel portion is extended to an end of the inner tube portion opposite to the tip-constricted tube portion . 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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