JPH0253131B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting thin-walled metal pipes using a plug-in joint in which an O-ring is housed in the inner periphery.

Traditionally, as a connection method for thin-walled metal pipes,
After inserting the metal pipe into the socket joint, the socket joint is formed with a reduced diameter part in the form of an annular concave groove that can be bited into the metal pipe, and the O-ring housed in the inner circumference of the socket joint is used to connect the socket joint to the metal pipe. A method for easily connecting metal pipes while sealing between the pipes and preventing the metal pipes from being pulled out from the plug-in joint by the biting action of a reduced-diameter portion formed in the plug-in joint into the metal pipe. It has been known.

By the way, the metal pipes connected by this method are cut to the desired length with a pipe cutter or the like, and if the metal pipes are left cut, the outer periphery of the ends of the metal pipes will have a pointed shape. When inserting the metal tube into the insertion joint, there is a risk that the end of the metal tube may damage the O-ring.

Therefore, conventionally, the ends of the metal pipes to be connected are chamfered in advance.

However, due to the thin wall thickness of the metal tube, it is only possible to chamfer a very small amount.
It is not possible to achieve both good and easy insertion of the metal pipe into the insertion joint and improvement of the sealing performance after connection by increasing the compression ratio of the O-ring.

In other words, if the compression ratio of the O-ring is made high, the end of the metal tube will get caught on the O-ring when the metal tube is inserted, preventing smooth insertion of the metal tube, making it difficult to insert the metal tube. Otherwise, the O-ring may be damaged by the end of the metal tube, or in extreme cases, a part of the O-ring may be damaged between the end of the metal tube and the side wall of the O-ring accommodating part of the plug-in joint on the side wall in the direction of insertion of the metal tube. It also ends up getting caught between the inner circumferential corner and being cut.

Therefore, in the past, it was necessary to set the compression ratio of the O-ring within a range that would not cause the above-mentioned problems when inserting the metal tube, and this was the only way to significantly improve sealing performance. The reality was that we could not hope for anything.

In addition, according to the conventional connection method, a reduced diameter part was formed in the O-ring accommodating part of the insertion joint toward the insertion direction of the metal tube to prevent the metal tube from being pulled out. When it is pulled out, the part of the metal pipe that has been deformed into a concave shape by the reduced diameter part of the insertion joint, that is, the part of the metal pipe that has been reduced in diameter, comes into contact with the O-ring. However, the compressibility of the O-ring decreases, making it impossible to expect the desired sealing effect and causing leakage.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to smoothly and smoothly insert a metal pipe into a plug-in joint without damaging the O-ring, even when the compression ratio of the O-ring is increased. In addition, even if the metal tube is pulled out after the connection is completed, the compressibility of the O-ring will not change at all, and the desired sealing effect can be maintained. Therefore, the metal tube can be used for a long time. The purpose of the present invention is to provide a method for connecting thin-walled metal tubes that can be easily connected in a state where an excellent sealing effect can be exerted over a long period of time.

The connecting method of the present invention solves this problem by bending the entire circumference of the end of the thin-walled metal pipe to be connected in advance toward the axis of the metal pipe to form a tapered shape. The insertion joint into which the metal tube is inserted has a protrusion on the inner periphery of the central part that blocks the end of the metal tube, and an O on the inner periphery outside of the protrusion.
An annular recessed groove-shaped O-ring accommodating portion for accommodating the ring is formed, the O-ring is accommodated in the O-ring accommodating portion, and from this state, the insertion joint is deformed into a tapered shape of the metal tube. inserting the end of the ring, and interfering with the outer circumferential surface of the end with the O-ring;
Furthermore, the end portion is inserted into the interior, and the O-ring is pressed against the outer circumferential surface of the metal tube so that it hits the protrusion, and then the O-ring is inserted into a portion of the insertion joint closer to the direction in which the metal tube is pulled out than the O-ring accommodating portion. , an annular concave groove-shaped reduced diameter portion capable of biting into the metal tube is formed to connect the metal tube in a manner that cannot be pulled out from the insertion joint.

Next, the method of the present invention will be specifically explained based on examples shown in the drawings.

In advance, the thin-walled metal tube 1 to be connected is cut to a desired length using a pipe cutter or the like, and the cut end 1a of the metal tube 1 is bent toward the axis of the metal tube 1 to form a tapered shape. Let it be deformed to reduce its diameter.

In this embodiment, as shown in FIG. 5, an annular blade 2 having an isosceles triangular cross section is provided protruding from the outer circumferential surface, and a pair of notches extend from the cutting edge 2a of the annular blade 2 to both sides in a tapering shape. A pipe cutter equipped with a cutting roller 4 having conical diameter reducing surfaces 3, 3 is used to simultaneously cut the metal tube 1 and bend and reduce the diameter of the end portion 1a. That is, the cutting roller 4 is pressed against the metal tube 1, the annular blade 2 bites into the metal tube 1, and the portions on both sides of the area where the annular blade 2 bites are moved inward by both diameter reduction working surfaces 3, 3. The cutting roller 4 is held in this state and rolled around the metal tube 1 to cut the metal tube 1 with the annular blade 2. The cut ends 1a, 1a are bent and deformed into a truncated conical shape with a tapered end at the diameter reduction working surfaces 3, 3. Therefore,
If a pipe cutter equipped with such a cutting roller 4 is used, the end 1 of the metal pipe 1 can be cut separately from the cutting operation.
It is convenient because it eliminates the trouble of having to perform the work of bending a to reduce its diameter.

Here, the structure of the insertion joint 5 for thin-walled pipes used in this embodiment will be explained. As can be understood by referring to FIG. 1, this insertion joint 5 is formed of a thin cylindrical metal material, and has annular groove-shaped O-ring accommodating portions 6 near both ends of the inner circumference. , 6, and each O-ring housing part 6
An O-ring 7 that can obtain a desired compression ratio according to the outer diameter of the metal tube 1 is housed in the inner circumference, and an annular protrusion 8 is formed by reducing the diameter at the center of the inner circumference. Side wall 6 of each O-ring accommodating portion 6 in the metal tube insertion direction (direction from both ends of the insertion joint 5 toward the center)
The inner peripheral corner part of a is a relief part 6b having an appropriate arc shape.
The side wall 6 on the metal pipe drawing direction (direction from the center to both ends of the insertion joint 5)
c is formed perpendicular to the axis of the insertion joint 5.

Then, the metal pipes 1 and 1 are connected to the above-mentioned insertion joint 5.
To make the connection via the metal tube 1, the metal tube 1 is first inserted into the insertion joint 5 until the end portion 1a of the metal tube 1 collides with the protrusion 8 and is locked therein (FIG. 4).

As the metal tube 1 is inserted into the insertion joint 5,
As shown in Fig. 2, the outer peripheral surface of the end 1a of the metal tube 1 is O.
Interfering with ring 7. That is, the end portion 1a of the metal tube 1
Since the metal tube 1 has a tapered bending shape that cannot be obtained by chamfering, the end 1a of the metal tube 1 does not get caught on the O-ring 7, and the inner circumference of the O-ring 7 part can be passed through smoothly. Furthermore, by forming an arc-shaped relief portion 6b on the side wall 6a of the O-ring accommodating portion 6 in the metal tube insertion direction, the end portion 1a of the metal tube 1 can be reduced in diameter to a tapered shape. At the same time, as shown in FIG.
The metal tube 1 is allowed to escape along the relief portion 6b without being caught and cut between the inner peripheral corner portion of the side wall 6a and the metal tube 1 can be inserted smoothly.

Therefore, the compressibility of the O-ring 7 is increased by bending the end 1a of the metal tube 1 into a tapered shape to reduce the diameter and interfering with the outer circumferential surface of the end 1a with the O-ring 7. Even in this case, the metal tube 1 can be smoothly and favorably inserted into the insertion joint 5 without damaging the O-ring 7.

When the metal tube 1 is inserted to the position where the end portion 1a collides with the protrusion 8, the metal tube is inserted from the end of the insertion joint 5, that is, the O-ring accommodating portion 6, using an appropriate diameter reducing tool. In the part closer to the pulling direction,
A diameter-reduced portion 9 in the shape of an annular concave groove that can be bitten into the metal tube 1 is formed, and the metal tube 1 is prevented from being pulled out from the insertion joint 5 by the biting action of the diameter-reduced portion 9 into the metal tube 1. (See Figure 1)
1 connection is completed.

In the connection structure of the metal tubes 1 and 1 obtained in this way, the compressibility of the O-ring 7 interposed between the metal tube 1 and the peripheral wall 6d of the O-ring accommodating portion 6 is made high. Therefore, the sealing performance of the O-ring 7 can be greatly improved compared to that obtained by the conventional method.

Moreover, since the diameter-reducing portion 9 that bites into the metal tube 1 and prevents it from being pulled out is provided at a location closer to the metal tube pull-out direction than the O-ring accommodating portion 6, the metal tube 1 can be pulled out to some extent. Even in this case, the metal tube portion 1b whose diameter is reduced by the diameter reducing portion 9 does not come into contact with the O-ring 7, as shown in FIG. 6, and the compressibility of the O-ring 7 changes. Never. Therefore, even if the metal tube 1 is pulled out, in other words, to put it extremely
As long as the O-ring 7 is not pulled out, the sealing effect of the O-ring 7 can be maintained as expected. In other words, the effective distance for preventing the metal tube 1 from being pulled out can be made extremely long.

Furthermore, if the side wall 6c of the O-ring accommodating portion 6 on the metal tube drawing direction side is formed perpendicular to the axis, even when high pressure acts inside the insertion joint 5, the O-ring accommodating portion 6 can be The ring 7 is attached to the side wall 6
c is securely received, and does not enter the gap 10 between the metal tube 1 and the insertion joint 5. Therefore, in order to prevent the O-ring 7 from entering the gap 10, it is not necessary to make the dimensional accuracy of the inner diameter of the insertion joint 5 particularly strict with respect to the outer diameter of the metal tube 1.

By the way, the present inventor conducted an experiment in order to compare and measure the pushing force on the same insertion joint using three types of metal tubes having the same diameter but different tube end shapes. As a result, for tubes with chamfered ends, the insertion force is only slightly reduced compared to tubes without chamfering, but
It was found that when the tube end was bent to reduce its diameter, the insertion force was reduced by more than 1/3 compared to when the tube end was chamfered.

Note that the amount of diameter reduction of the end portion 1a of the metal tube 1 is set appropriately depending on various conditions such as the compression ratio of the O-ring 7. Therefore, the diameter reduction range is not limited.

As is clear from the above description, according to the method for connecting thin-walled metal tubes of the present invention, the end portions of the metal tubes to be connected are deformed in diameter to a tapered shape, and the diameter is reduced. Since the outer peripheral surface of the deformed end interferes with the O-ring of the insertion joint, the O
Even when the compression ratio of the ring is high, the insertion of the metal pipe into the bayonet joint can be carried out smoothly and smoothly without damaging the O-ring, which is impossible to achieve with conventional methods. Metal pipes can be easily connected while exhibiting high sealing performance that was previously impossible.

Furthermore, since the diameter-reducing part that bites into the metal tube and prevents it from being pulled out is formed at a location closer to the metal tube pull-out direction than the O-ring accommodating part, even if the metal tube is pulled out, the diameter reduction part can be prevented from being pulled out. The metal tube portion that has been deformed into a concave shape by the diameter portion does not come into contact with the O-ring, and the desired sealing effect can be maintained without changing the compressibility of the O-ring. Therefore, an excellent sealing effect can be maintained for a long period of time.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention.
The figure is a longitudinal side view of the upper half showing the connection completed state, Figures 2 to 4 are longitudinal side views of the main part showing the insertion state of the metal tube in order, and Figure 5 is the cut state of the metal tube. Fig. 6 is a longitudinal sectional side view of the main part showing the state in which the metal pipe is pulled out after the connection is completed, and Fig. 7 is the state in which high pressure is applied within the plug-in joint after the connection is completed. FIG. 1... Metal tube, 1a... End of metal tube, 5...
Plug-in joint, 6...O-ring housing part, 7...O-ring, 8...projection, 9...diameter reduction part.

Claims (1)

[Claims] 1. In advance, bend the entire circumference of the end of the thin-walled metal pipe to be connected toward the axis of the metal pipe to form a tapered shape, and then insert the metal pipe into the insertion joint into which the center of the pipe is inserted. A protrusion for blocking the end of the metal tube is formed on the inner periphery of the part, and an annular groove-shaped O-ring accommodating part for accommodating the O-ring is formed on the inner periphery outside the protrusion. An O-ring is accommodated in the ring accommodating portion, and from this state, the tapered end of the metal tube is inserted into the insertion joint so that the outer peripheral surface of the end interferes with the O-ring, and The end thereof is inserted into the interior, and the O-ring is brought into contact with the protrusion while being pressed against the outer circumferential surface of the metal tube, and then placed in a part of the insertion joint closer to the direction in which the metal tube is pulled out than the O-ring accommodating part, A method for connecting thin-walled metal tubes, characterized in that an annular concave groove-shaped reduced diameter portion that can cut into the metal tube is formed to connect the metal tube so that it cannot be pulled out from the insertion joint.