Resinous tube joint

1. A resin pipe joint comprising:

a synthetic resin-made joint body including an inner cylinder portion to which an end portion of a synthetic resin-made tube is externally fittable and attachable while being flared, and an external thread portion; and

a synthetic resin-made union nut including: an internal thread portion which is screwable with said external thread portion; a first pressing portion which is actable on a small-diameter portion of a flaring changing region in a flared portion of said tube, said flared portion being externally fitted to said inner cylinder portion; a second pressing portion which is actable on a large-diameter portion of said flaring changing region; and a pressing inner peripheral portion which is externally fittable to a flared straight portion of said flared portion, and

wherein said resin pipe joint is configured so that, by a screw advancement of said union nut in a direction of an axis of said joint body, the screw advancement being caused by screwing said internal thread portion to said external thread portion in a state where said tube is externally fitted and attached to said inner cylinder portion and said flared portion is formed, said pressing inner peripheral portion is pressingly contacted with and externally fitted to said flared straight portion, said large-diameter portion of said flaring changing region is pressed in the direction of the axis by said second pressing portion, and said small-diameter portion of said flaring changing region is pressed in the direction of the axis by said first pressing portion, and set so that, after start of the pressing of said large-diameter portion of said flaring changing region by said second pressing portion, the pressing of said small-diameter portion of said flaring changing region by said first pressing portion is started,

said inner cylinder portion including an end-tapered cylinder portion and a constant-diameter straight barrel cylinder portion which is formed in succession to a large-diameter side of the end-tapered cylinder portion,

a pressing face is formed on the second pressing portion, an inner diameter of the pressing face is formed to be larger than a maximum diameter of a cylindrical shape of the inner cylinder portion and smaller than a diameter of an inner peripheral face of the pressing inner peripheral portion, the pressing face being perpendicular to the axis; and

when the joint is assembled with a tube, said flaring changing region is put over said end-tapered cylinder portion, and said flared straight portion of said flared portion is externally fitted to said straight barrel cylinder portion.

2. A resin pipe joint according to claim 1 , wherein said pressing inner peripheral portion is pressingly contacted with and externally fitted to said flared straight portion in a degree in which a radial gap is not formed between said pressing inner peripheral portion and said flared straight portion, and co-rotation of said flared portion due to fastening of said union nut does not occur.

3. A resin pipe joint according to claim 2 , wherein a cover cylinder portion which covers said inner cylinder portion and forms a radial gap that allows said tube to be inserted is formed in said joint body, and said union nut is made of a transparent synthetic resin.

4. A resin pipe joint according to claim 1 , wherein a cover cylinder portion which covers said inner cylinder portion and forms a radial gap that allows said tube to be inserted is formed in said joint body, and said union nut is made of a transparent synthetic resin.

5. A resin pipe joint according to claim 4 , wherein said external thread portion is formed also on an outer peripheral portion of said cover cylinder portion.

6. A resin pipe joint according to claim 1 , wherein said end-tapered cylinder portion of said inner cylinder portion causes said tube to be gradually flared.

7. A resin pipe joint according to claim 1 , wherein said straight barrel cylinder portion is extended to an end of said inner cylinder portion, said end being opposite to said end-tapered cylinder portion.

8. A resin pipe joint according to claim 1 , wherein both said joint body and said union nut are made of a fluorine resin.

9. A resin pipe joint according to claim 1 , wherein

said first pressing portion is a first peripheral edge comprising a first pressing face, the first pressing face is perpendicular to the axis of said joint body, and

said second pressing portion is a second peripheral edge comprising a second pressing face, the second pressing face is perpendicular to the axis of said joint body.

10. A resin pipe joint according to claim 9 , wherein

said resin pipe joint is configured so that, by screw advancement of said union nut in the direction of the axis of said joint body, said second peripheral edge is in contact with said flaring changing region while the first peripheral edge is not in contact with said flaring changing region, and then by further screw advancement of said union nut in the direction of the axis of said joint body, said second peripheral edge presses said flaring changing region and the first peripheral edge is in contact with said flaring changing region.

11. A resin pipe joint according to claim 1 , wherein

said resin pipe joint is configured so that, by screw advancement of said union nut in the direction of the axis of said joint body, said second pressing portion is in contact with said flaring changing region while the first pressing portion is not in contact with said flaring changing region, and then by further screw advancement of said union nut in the direction of the axis of said joint body, said second pressing portion presses said flaring changing region and the first pressing portion is in contact with said flaring changing region.

12. A resin pipe joint according to claim 1 , wherein

the resin pipe joint consists of:

the synthetic resin-made joint body;

the synthetic resin-made tube; and

the synthetic resin-made union nut.