JPH0689866B2 - Pipe fitting - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe joint for connecting water-supply pipes, hot-water supply pipes, etc., for example, connecting pipes made of synthetic resin, and more specifically, to a cap nut. The present invention relates to a pipe joint in which a screw portion is not likely to be damaged or deformed by tightening when connecting both connecting pipes with each other.

(Prior Art) It is necessary to connect, for example, a synthetic resin connecting pipe forming a water supply passage or a hot water supply passage so as not to be easily detached and to prevent water from leaking from the connection portion. When connecting the connecting pipes, for example, as disclosed in Japanese Utility Model Laid-Open No. 61-22991, a method of connecting the end portions of the connecting pipes by screw connection through a pipe joint is relatively simple. It is often used because it has a strong fastening force.

When this connecting structure is outlined based on FIG. 9, reference numeral 51 in the drawing denotes a pipe joint main body, and the pipe joint main body 51 has one connecting pipe 57.
A cylindrical portion 54 into which an end portion of the cylindrical portion 54 is inserted, and a flange portion 60 integrally projecting from one end portion of the cylindrical portion 54 in the outer peripheral direction are provided. A male screw portion 52 is formed on the outer circumference of the cylindrical portion 54, and a notch portion 53 is formed at the tip of the cylindrical portion 54 so that the diameter of the tip can be reduced inward. Reference numeral 40 denotes a connecting cylinder body provided with a nut portion 41 to be engaged with the collar portion 60 of the pipe joint body 51, and a male screw portion 49 at an end portion of the connecting cylinder body 40 has a connecting pipe 55 on the other side. Are screwed together. 43 is a packing attached to the outer peripheral surface of a guide portion 42 provided at the tip of the connecting tubular body 40, and 44 is a female screw portion 45 that is screwed into the male screw portion 52 of the pipe joint body 51 is formed on the inner periphery of the front portion. A cap nut having a tapered portion 46 provided on the inner circumference of the base portion.

When connecting a pair of connection pipes 55, 57 such as a hot water supply pipe or a water supply pipe using the pipe joint having the above-described configuration, as shown in the figure, the nut portion 41 of the connection tubular body 40 is connected to the flange of the pipe joint body 51. Department
The pipe joint main body 51 is attached to the outside of the connecting tubular body 40 by fitting 60 from the outside, and the female screw portion 45 of the cap nut 44 is screwed into the male screw portion 52 of the pipe joint main body 51. Then, the male screw portion 49 of the connection tubular body 40 is screwed into the one connection pipe 55, and the guide portion 42 provided at the other end of the connection tubular body 40, and the cylindrical portion 54 of the pipe joint body 51. The end portion of the other connecting pipe 57 is inserted into the gap portion 56 formed between the two. In this state, the cap nut 44 is tightened with a tool such as a spanner until the tip of the cap nut 44 comes into contact with the end face of the flange portion 60 of the pipe joint body 51. As the cap nut 44 moves to the side of the pipe joint body 51, the tapered portion 46 of the cap nut 44 presses the tip of the cylindrical portion 54 of the pipe joint body 51 inward, and the diameter of the tip of the cylindrical portion 54 is reduced. By pressing the outer surface of the connecting pipe 57 over the entire circumference, the inner surface of the connecting pipe 57 is brought into pressure contact with the outer surface of the packing 43.

In this manner, the inner peripheral surface of the connecting pipe 57 is elastically pressed against the packing 43, and the connecting pipe 57 is sandwiched between the connecting tubular body 40 and the tubular joint main body 51, so that the sealing property is good, and The connection pipe 57 is firmly connected to surely prevent the liquid from leaking from this connection portion.

(Problems to be Solved by the Invention) However, piping such as a hot water supply pipe is usually performed in a narrow and dark place such as under the ceiling or under the floor. Therefore, when the cap nut 44 is rotated relative to the pipe joint main body 51 to bring the tip end surface of the cap nut 44 into contact with the end surface of the flange portion 60, it is not possible to visually recognize that the end surfaces have abutted against each other. Often happens.

Conventionally, in such a case, the cap nut 44 is gradually tightened while being careful so that the end surface of the cap nut 44 has a pipe joint body 51.
The increase in tightening resistance after contacting the end surface of the collar portion 60 of the tool is detected by hand through the tool, and the tightening is stopped when it becomes difficult to tighten, but the tightening resistance acting on the tool gradually and Since it rises continuously, it is not possible to know the appropriate final tightening time, and the end face of the cap nut 44 will be the flange 60 of the pipe joint body 51.
Despite being in contact with the end face, the cap nut 44
Was sometimes tightened.

In this case, a strong axial force may act on the female screw portion 45 of the cap nut 44 and the male screw portion 52 of the pipe joint body 51 to damage or deform these screw portions. When the screw portion is damaged or deformed, the cap nut 44 retracts from the predetermined tightening position, the tightening force of the connecting pipe 57 by the cap nut 44 decreases, and the connecting portion of the connecting pipe 57 cannot be completely sealed. Liquid may leak. Especially when the connection pipe is made of synthetic resin, aluminum, etc., considering corrosion resistance and productivity, the strength of the threaded portion is relatively small, and the tightening force may be a little stronger than the specified tightening force. The threaded portion is damaged or deformed.

On the other hand, for example, in order to prevent damage and deformation of the female threaded portion 45 of the cap nut 44 and the male threaded portion 52 of the pipe joint body 51, for example, the thread of these threaded portions is increased or the threaded coupling portion is lengthened. It is also possible to increase the strength of the threaded portion. However, when formed in this way, there is a drawback that the diameter and length of the pipe joint increase, which is disadvantageous in terms of cost and is not suitable when connecting the connecting pipes 55 and 57 in a narrow place.

The present invention solves the above-mentioned drawbacks, and the purpose thereof is to be able to always detect the optimum final tightening time even when connecting the connecting pipe in a place where the connecting portion cannot be seen, and to damage or deform the screw part. The object is to provide a pipe joint that prevents the occurrence of the above and obtains a reliable sealing performance. Still another object of the present invention is to provide a pipe joint that can reliably seal at a connecting portion without increasing the size of the pipe joint.

(Means for Solving the Problems) A pipe joint of the present invention is a cylindrical portion externally fitted to an end portion of a connecting pipe and having a male screw portion formed on the outer periphery thereof, and an outer peripheral direction protruding from one end portion of the cylindrical portion. A bag having a pipe joint body having a flange portion provided therein, and a female screw portion that is screwed into the male screw portion of the pipe joint body is formed on the inner circumference of the front portion, and a taper portion is provided on the inner circumference of the base portion. A nut, and the contact surface formed at the tip of the cap nut is formed on the flange portion of the pipe joint body by screwing the female screw portion of the cap nut and the male screw portion of the pipe joint body. A pipe joint that is close to the contact surface and presses the outer surface of the connection pipe that is externally fitted to the cylindrical portion of the pipe joint body by pressing the cap nut inwardly. The engaging portion provided on either one of the surface or the contact surface of the flange portion, and any of the above And a protrusion which is provided on one side and is engageable with the engaging portion, thereby achieving the above object.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in FIG. 1, a pipe joint according to the present invention is configured to have a pipe joint body 1 and a cap nut 2, and a pair of connection pipes such as a water supply pipe and a hot water supply pipe using a connection cylinder body 3. 4, 5 are connected.

As shown in FIGS. 1 to 3, the connecting tube pair 3 is formed of a synthetic resin material or a corrosion resistant material such as aluminum into a substantially cylindrical shape. As described above, one end of the connecting cylinder 3 is connected to the connecting pipe 4 such as a hot water supply pipe or a water supply pipe.
30 and the other end of the connecting cylinder 3 is a cylindrical guide part.
31 is formed. A rectangular, for example, hexagonal nut portion 32 is provided at a substantially central portion of the connection tubular body 3, and a connection portion 30 and a guide portion 31 extend from the nut portion 32. An annular groove 33 is formed on the side of the guide portion 31 on which the connecting pipe 5 is inserted and on the outer periphery of the end portion, and a packing 6 is mounted in the annular groove 33. The outer diameter of this packing 6 is the guide part
The outer diameter is approximately equal to or slightly smaller than 31.

The pipe joint body 1 is formed of a synthetic resin material or a corrosion-resistant material such as aluminum into a substantially cylindrical shape, like the connecting cylinder body 3. The pipe joint body 1 includes a cylindrical portion 14 having an externally threaded portion 15 formed on the outer periphery thereof, and a flange portion 10 integrally projecting from one end of the cylindrical portion 14 in the outer peripheral direction. The cylindrical part
A plurality of notches 16 that are long in the axial direction are formed at the tip of 14 so that the tip of the cylindrical portion 14 can be reduced in diameter by an external pressing force. The inner diameter of the cylindrical portion 14 is substantially equal to or slightly larger than the outer diameter of the connecting pipe 5. The length of the cylindrical portion 14 is such that the tip end of the notch portion 16 is an annular groove 33 provided on the outer periphery of the guide portion 31 of the connecting cylinder body 3.
It is set to correspond to the position of. The collar part
10 has a flat portion 10a and a corner portion 10b on the outer surface and is formed, for example, in the shape of a hexagonal side nut, and a tightening tool such as a spanner can be engaged with the outside of the collar portion 10 to rotate or fix it. ing. The open side surface of the collar portion 10 is formed in a shape that can be externally fitted to the nut portion 32 of the connecting cylinder body 3.

When the flange portion 10 of the pipe joint body 1 is fitted onto the nut portion 32 of the connecting cylinder body 3, the cylindrical portion 14 of the pipe joint body 1 is concentric with the guide portion 31 of the connecting cylinder body 3. Located in the guide section 31
A gap portion 7 into which the connecting pipe 5 can be inserted is formed between the outer surface of the cylindrical portion 14 and the inner surface of the cylindrical portion 14.

The cap nut 2 mounted around the pipe joint body 1 is formed of a synthetic resin material or a corrosion-resistant material such as aluminum into a substantially cylindrical shape, like the pipe joint body 1 and the connecting cylinder 3. A female screw portion 20 that is screwed into a male screw portion 15 on the outer circumference of the cylindrical portion 14 is formed on the inner circumference of the front portion of the cap nut 2, and a taper portion 21 is formed on the inner circumference of the base portion of the cap nut 2 which is reduced in diameter toward the base end. Is formed, and an opening 24 having an inner diameter slightly larger than the outer diameter of the connecting pipe 5 is provided on the base end side thereof.

When the pair of connecting pipes 4 and 5 such as a hot water supply pipe and a water supply pipe are connected using the pipe joint having the above-described configuration, the following process is performed.

As shown in FIG. 1, the connecting portion 30 of the connecting tubular body 3 is screwed into the end portion of one connecting pipe 4, and the pipe joint body 1 is externally fitted to the outer periphery of the nut portion 32 of the connecting tubular body 3. The cap nut 2 is loosely screwed onto the outside of the pipe joint body 1. Then, the connecting pipe 5 is inserted through the opening 24 of the cap nut 2, and the end of the connecting pipe 5 is formed between the cylindrical portion 14 of the pipe joint body 1 and the guide portion 32 of the connecting tubular body 3. Inserted into the inner part of the gap portion 7, and while the pipe joint body 1 is fixed with a tool or the like, the cap nut 2 is turned with a tool or the like so that the female screw portion 20 of the cap nut 2 is the male screw portion of the cylindrical portion 14. Screw to 15. By the screwing of the cap nut 2, the cap nut 2 advances toward the flange portion 10 of the pipe joint body 1, and the contact surface formed at the tip of the cap nut 2
22 is an abutment surface 12 formed on the side surface of the collar portion 10 of the pipe joint body 1.
When the cap nut 2 is tightened until it almost comes into contact with, the tip portion of the cylinder portion 14 in which the notch portion 16 is formed is pressed inward by the taper portion 21 of the cap nut 2, and as a result, the tip portion is reduced in diameter. Then, the end portion of the connecting pipe 5 is pressed inward, and the inner surface of the connecting pipe 5 is pressed against the outer surface of the packing 6,
This portion is hermetically sealed and the connecting pipe 5 is prevented from coming off the joint.

The pipe joint of the present invention has a protrusion 23 on the contact surface 22 of the cap nut 2.
And the cap nut 2 is provided on the contact surface 12 of the collar portion 10.
As the contact surface 22 of the cap nut 2 approaches the flange portion 10 by tightening, the engaging portion 11 with which the protrusion 23 engages is provided as a recess.

For example, six protrusions 23 are provided on the contact surface 22 of the cap nut 2 at appropriate intervals in the circumferential direction. This protrusion
As shown in FIGS. 4 and 5, 23 is formed of a substantially trapezoidal flat plate, and the end surface on the side of the pipe joint body 1 is a plane parallel to the contact surface 22. An inner peripheral side edge 23a and an outer peripheral side edge 23b of the protrusion 23 are formed substantially parallel to the circumferential direction, and a side edge 23 of the protrusion 23 on the screwing direction side of the cap nut 2 is formed.
The side edge 23d of the protrusion 23 on the side opposite to c and the screwing direction substantially coincides with the radial direction.

At the edge of the contact surface 12 of the flange 10 of the pipe joint body 1, an engaging portion 11 with which the projection 23 can be engaged is provided as a recess. When the contact surface 22 of the cap nut 2 is brought into contact with the contact surface 12 of the collar portion 10, the engaging portion 11 is arranged at a position corresponding to the protrusion 23, that is, six engaging portions are provided. It is recessed. The engaging portion 11
Is recessed in the flat portion 10a of the collar portion 10 in the vicinity of a corner portion 10b on the screwing direction side of the cap nut 2, and the engaging portion 11 is formed in a shape that is open in the cap nut 2 direction and outward direction. . Then, the inner peripheral edge of the protrusion 23 is formed in the engaging portion 11.
The protrusions 23 are engaged with the engaging portions 11 by inserting a portion surrounded by the 23a and the side edge 23c in the screwing direction.

Further, the cap nut 2 is screwed into the pipe joint body 1 so that the contact surface 22 is brought into contact with the contact surface 12 of the pipe joint body 1, and
When the protrusion 23 is located at the center of the flat portion 10a of the collar portion 10,
The inner peripheral side edge 23a of the protrusion 23 is arranged outside the flat portion 10a, and the protrusion 23 does not slidably contact the end face of the flange 10. And the protrusion 23
In the state where is located near the corner 10b of the collar 10, the protrusion 23
The inner peripheral side edge 23a is in contact with the end surface of the collar portion 10. The projecting dimension of the projecting portion 2 from the contact surface 22 corresponds to one pitch of the female thread portion 20 of the cap nut 2. Therefore, after the end surface of the projecting portion 23 comes into contact with the contact surface 12 of the collar portion 10, a bag is formed. When the nut 2 is rotated once, the protrusion 23 is completely engaged with the engaging portion 11, and the contact surfaces 12 and 22 are in contact with each other.

Therefore, as described above, when connecting the pair of connecting pipes 4 and 5 using this pipe joint, the cap nut 2 is tightened so that the abutment surface 22 of the cap nut 2 of the flange portion 10 of the pipe joint body 1 becomes. When the projection 23 engages with the engaging portion 11 of the pipe joint body 1 in the state of approaching the contact surface 12, a strong tightening resistance required for further rotating the cap nut 2 is applied to the tool as a reaction force. This will act and the tightening force will increase rapidly. When the cap nut 2 is tightened by further applying a force to the tool, the protrusion 23 or the engaging portion 11, or the protrusion 23 and the engaging portion 11 are deformed, so that the protrusion is indicated by a phantom line in FIG. 23 rides over the engaging portion 11, the engagement between the protruding portion 23 and the engaging portion 11 is released, and the protruding portion 23 slides on the flat portion 10a of the collar portion 10 at the next position. When the engagement is released, only the reaction force due to the deformation of the protrusion 23 is received, so that the tightening force sharply decreases. continue,
When the cap nut 2 is tightened, the cap nut 2 becomes the male screw part.
Since the pipe joint body 1 is gradually approached by the screwing of the female screw portion 15 and the female screw portion 20, the protrusion 23 is engaged with the engaging portion 11 with a stronger engaging force than the previous engagement. In order to release this engagement, since the engagement surface between the projection 23 and the engagement portion 11 becomes large, it is necessary to apply a stronger tightening force than the previous time to the tool to rotate the cap nut 2.

In this way, the operator tightens the tool 22 with the tool until the contact surface 22 of the cap nut 2 contacts the contact surface 12 of the pipe joint body 1 and a desired sealing property is obtained. Since it is possible to detect a sudden change in strength with respect to resistance, judge this point as an approximate proper final tightening position, and stop tightening when the next strong tightening resistance is felt. 22 is almost in contact, and proper sealing performance can be obtained.

Since the abrupt increase in the tightening force due to the engagement between the protrusion 23 and the engaging portion 11 acts only in the circumferential direction, it does not affect the tightening of the screw, and does not deform or damage the screw, resulting in It is possible to connect by applying a large tightening force to.

In particular, when the inner peripheral side edge 23a of the protrusion 23 does not contact the contact surface 12 of the collar portion 10 and when it contacts the contact surface 12 as in the above-described configuration, the cap nut 2 is tightened. like,
Since the positions of the engaging portion 11 and the projecting portion 23 are set respectively, when the projecting portion 23 is located outside the contact surface 12 of the engaging portion 11 when the cap nut 2 is tightened, Is in a state in which the axial contact force from the contact surface 12 of the pipe joint body 1 and the resistance in the rotation direction are not received, and the tool simply inserts the female screw portion 20 of the cap nut 2 and the male screw portion 15 of the pipe joint body 1. Since only the force necessary for screwing is applied, the change in tightening resistance becomes very large, and the proper tightening determination time can be easily detected.

Moreover, in order to tighten the cap nut 2 as described above, a tightening force sufficient to release the engagement between the engaging portion 11 and the protrusion 23 is added to the screwing force, so that it is relatively strong. You need strength, and at this point you can judge that it is the final tightening point. At this time, the tightening force mainly acts as a force required to release the engagement between the engaging portion 11 and the protrusion 23, and by this tightening, a strong tightening is applied to the screwed portion of the male screw portion 15 and the female screw portion 20. There is no possibility that force will act and damage or deform the threaded portion.

(Other Embodiment) As shown in FIG. 6, the protrusion 23 may be formed in a cylindrical shape. Also in this embodiment, the collar portion is the same as in the above embodiment.
An engaging portion 11 is provided at a position in the vicinity of a corner of the flat portion 10a of the flat nut 10a in the screwing direction of the cap nut 2. When the cap nut 2 is tightened and rotated, the protrusion 23 is engaged. By arranging inside 11 and tightening the cap nut 2 further,
The projection 23 is configured to be switched between the state where the projection 23 is disengaged from the recess.

(Second Embodiment) As shown in FIG. 7, the protrusion 23 may be formed into a rectangular side surface. In this embodiment, the side edge 23 on the screwing direction side of the protrusion 23
The c is formed substantially parallel to the radial direction of the cap nut 2.
The structure of the pipe joint body 1 is the same as that of each of the above-described embodiments. Therefore, according to this embodiment, since the side edge 23a of the projection 23 on the screwing direction side and the inner wall of the engaging portion 11 are in contact with each other in a planar state as shown in the figure, the projection 23 is screwed from this state. A stronger tightening force is required to tighten in the mating direction. As a result, the fluctuation in the strength of the tightening force becomes large, and there is an advantage that the final tightening time can be easily determined.

(Other Example 3) As shown in Fig. 8, the pipe joint according to the present invention can be applied to a case where a pair of connecting pipes 4 and 5 are connected using a pair of cap nuts 2 and 2. .

In this embodiment, the pipe joint body 1 is constructed by providing cylindrical portions 14 and 14 on both sides of the central collar portion 10, and the female screw portion 20 of the cap nut 2 is attached to the male screw portion 15 formed on the outer periphery of the square cylindrical portion 14. They are designed to be screwed together. An annular packing 6 is arranged in an annular groove formed between the tapered portion 21 formed on the inner surface of the cap nut 2 and the end of the cylindrical portion 14 of the pipe joint body 1. A metallic connecting cylinder 3 is inserted and arranged in the end of the connecting pipe 5 inserted into the cylindrical portion 14 to reinforce the end of the connecting pipe 5. When connecting the pair of connecting pipes 4 and 5 using the pipe joint having such a configuration, the end portions of the connecting pipes 4 and 5 are respectively inserted and arranged in the cylindrical portion 14 of the pipe joint body 1, Tighten the cap nut 2. Then, cap nut 2
As a result of the taper portion 21 pressing the packing 6 inwardly, the connecting pipes 4 and 5 are elastically sandwiched between the packing 6 and the connecting cylinder body 3, and the connecting pipes 4 and 5 are connected via the pipe joint. The connection pipes 4 and 5 are firmly connected, and the connection pipes 4 and 5 and the pipe joint body 1 are hermetically sealed via the packing 6.

A deformable protrusion 23 is formed on the tip end surface of the cap nut 2, and an engaging portion 11 that engages with the protrusion 23 is recessed on both end surfaces of the flange portion 10 of the pipe joint body 1. And each bag nut 2
It is configured such that the tightening force fluctuates due to the engagement between the projection 23 and the engaging portion 11 when tightening the. Even in this case, the cap nut 2 is tightened so that the packing 6 is pressed at a position where the contact surface 22 of the cap nut 2 is brought into contact with both the contact surfaces 12 of the flange portion 10 so that good sealing performance can be obtained. The dimensions of the cap nut 2, the pipe joint body 1 and the packing 6 are set.

In addition, in the present invention, the engaging portion 11 is connected to the pipe joint body 1
However, the engaging portion 11 may be provided on the cap nut 2 side and the engaging portion 11 may be provided on the cap nut 2 side. The numbers of the engaging portions 11 and the protrusions 23 are not limited. Further, the numbers of the protrusions 23 and the engaging portions 11 may be different.

Further, the shape of the collar portion 10 is not limited to the hexagonal nut shape, and may be, for example, a polygon such as a quadrangle or a pentagon, a side surface circle, or an ellipse. The shape of the connecting tubular body 3 is not limited to one in which the guide portion 31 is provided only on one side, and is provided so as to branch in two directions.
Alternatively, the present invention can be applied to a device that is branched in three directions.

(Effect of the invention) As described above, according to the present invention, the engaging portion is provided on either the contact surface of the cap nut or the contact surface of the flange portion of the pipe joint body, and the engaging portion is provided on the other one. Since there is provided a protrusion that is disengageable from the state in which it is engaged with the engaging portion by tightening the cap nut, the cap nut and the pipe joint main body are rotated relative to each other, and Until the contact surfaces are brought close to each other and the desired sealing structure is obtained, the force required for tightening varies greatly due to the engagement and disengagement of the protrusion and the engaging part. Since it is possible to easily detect the change in tightening resistance, it is sufficient to judge that this time point is an almost proper final tightening position and stop tightening the cap nut when the next strong tightening resistance is felt. Therefore, even when connecting the connection pipe in a place where the connection point is not visible, such as in the ceiling or under the floor, the proper tightening position can be accurately determined, and the cap nut can be overtightened as in the conventional method. The threaded portion of the pipe joint body is not damaged or deformed, the connection pipe can be reliably sealed by the cap nut, and the tightening force can be made uniform.

Further, even when the pipe joint is formed of a member that is relatively easily deformed compared to iron such as synthetic resin or aluminum, the connecting pipe can be securely connected without increasing the diameter and length of the threaded portion, so it is narrow. It is also advantageous when piped to a location.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view showing an example of the pipe joint of the present invention with a connecting pipe connected, and FIG. 2 is a front view of the pipe joint.
FIG. 3 is a longitudinal sectional view of the pipe joint, FIG. 4 is a transverse sectional view of the pipe joint, FIG. 5 is an enlarged sectional view of an essential part thereof, and FIG. 6 is a transverse pipe joint of another embodiment of the present invention. Sectional drawing, FIG. 7 is a transverse sectional view of a pipe joint of still another embodiment of the present invention, FIG. 8 is a vertical sectional view of a pipe joint of yet another embodiment of the present invention, and FIG. 9 is of a conventional pipe joint. FIG. 1 ... Pipe joint body, 2 ... Cap nut, 3 ... Connection cylinder,
4 ... Connection pipe, 5 ... Connection pipe, 10 ... Collar part, 11 ... Engagement part, 14 ... Cylindrical part, 15 ... Male screw part, 20 ... Female screw part,
21 …… Tapered part, 23 …… Protruded part.

Claims (2)

[Claims] 1. A pipe joint body having a cylindrical portion externally fitted to an end portion of a connecting pipe and having a male screw portion formed on the outer periphery thereof, and a flange portion protruding from one end portion of the cylindrical portion toward the outer peripheral direction. And a cap nut in which a female screw portion to be screwed into the male screw portion of the pipe joint body is formed on the inner circumference of the front portion and a taper portion is provided on the inner circumference of the base portion. The contact surface formed on the tip of the cap nut is brought close to the contact surface formed on the flange portion of the pipe joint body by screwing the male part and the male screw part of the pipe joint body, and the taper of the cap nut Is a pipe joint for pinching the outer surface of the connection pipe externally fitted to the cylindrical portion of the pipe joint body by pressing inward of the portion, and one of the contact surface of the cap nut or the contact surface of the flange portion. And an engaging portion provided on the other of the engaging portions, Pipe joint comprising a projection that, the. 2. The cap portion is formed in a nut shape having a flat portion and a corner portion on an outer side surface thereof, and the cap nut is provided at a position near the corner portion of the flat portion on the screwing direction side of the cap nut. The engaging portion is formed so as to open in the direction toward the outside and the protrusion provided on the cap nut is arranged outside the flat portion at the central position of the flat portion. The described pipe fitting.