JPH0929362A - Device and method for forming connecting end of pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce forming process and to prevent fractures of a pipe stock by continuously carrying out a preliminary process in the first and the second forming processes, forming an annular flange part in the third process, forming the first and the second tubular parts in the fourth process and forming an annular projection part in the fifth process. SOLUTION: In the second forming process, a ratio of length in the axial direction of a truncated cone shape tubular part, which is formed in the first preliminary process and which is constituted of a large and a small diameter tubular part to be connected to the tapered end of a pipe stock and a tapered part for connecting these tubular parts, to the small diameter tubular part is set as 2:1 to 1.8:1.2, and these parts are reduced into a continuous shape with such ratio retained. Then, an annular flange part 5 is projection-molded with the tapered part of the pipe stock end side held in, continuously formed with a ratio of length in the axial direction of the truncated cone shaped tubular part, which is tapered on one end of the annular flange part 5, to the small diameter tubular part set as 1:2 to 0.7:1.3. After that, the first tubular part 6 having a level vertical to the axial direction is formed as is the second tubular part 7, and then an annular projection part 8 is formed on the tip end side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the molding of a pipe end used for a refrigerant pipe of an automobile air conditioner, and more particularly, a pipe connection end for forming a pipe end connection structure connected by a union joint. The present invention relates to a device and a method for molding a connecting end of a pipe.

[0002]

2. Description of the Related Art The structure of a connecting end portion of a pipe for connecting an end portion of a pipe used for a refrigerant pipe of a conventional automobile air-conditioning apparatus with a union joint is located farther from an axial end of the pipe material than the pipe material. A flange portion formed with a large outer diameter, a first tubular portion formed with a smaller outer diameter than the flange portion at a position adjacent to one end side in the axial direction of the flange portion, and the first A second tubular portion formed with a smaller outer diameter than the first tubular portion at a position adjacent to the axial one end side of the tubular portion, and adjacent to the axial one end side of the second tubular portion. Smaller than the flange portion and in the second position
It is formed by providing a third tubular portion having an outer diameter larger than that of the tubular portion.

As a method of molding the connecting end portion of the pipe having the above-mentioned structure, the pipe material fixed to the clamp is provided at one end in the axial direction and a portion in the vicinity thereof along the axial center of the pipe material, relative to the pipe material. The flange portion, the first tubular portion, the second tubular portion, and the third tubular portion are formed by performing plastic working a plurality of times by a plurality of punches that are movable in a general manner (Japanese Patent Laid-Open No. H05-58242). -337576 gazette).

[0004]

However, according to the molding method described in the prior art, each molding of the flange portion, the first tubular portion, the second tubular portion, and the third tubular portion is performed. The molding is performed by a two-step processing method in which a preforming process is performed. Therefore, six steps are required to form the flange portion, the first tubular portion, the second tubular portion, and the third tubular portion. In addition, the end of the pipe material is expanded in the formation of the flange portion, and then is reduced in diameter in the formation of the third tubular portion, and the diameter of the reduced pipe end is expanded again. There is a problem that the end portion of the raw pipe is liable to be broken at the time of expanding the pipe again, and as a result, the strength of the outermost end portion of the raw pipe forming the third tubular portion is weakened.

The present invention has been made in view of the problems of the prior art, and its object is to:
(EN) A manufacturing apparatus for a connecting end portion of a pipe and a molding method for the same, which can reduce the number of molding steps by beating and reduce the occurrence of breakage of a pipe material caused by repeating expansion and contraction of a pipe. .

[0006]

In order to achieve the above object, a pipe connecting portion molding apparatus according to the present invention has a pipe material having an outer diameter larger than that of the pipe material at a position distant from one axial end of the pipe material. And a first tubular portion formed with a smaller outer diameter than the annular collar portion at a position adjacent to the one end side in the axial direction of the annular collar portion, and the first tubular portion of the first tubular portion. A second tubular portion formed with an outer diameter smaller than the first tubular portion at a position adjacent to the one axial end side, and an annular collar portion at a position adjacent to the axial one end side of the second tubular portion. In forming a connecting end of a pipe having an annular ridge formed with an outer diameter that is smaller than the second tubular portion and is larger than the second tubular portion, one end in the axial direction of the pipe material and a portion in the vicinity thereof are expanded and A first pad for performing a first preliminary step of forming a relatively large-diameter cylindrical portion. And a conical tubular portion having a large-diameter body portion connected to the taper portion on the raw pipe side formed in the first preliminary step, a small-diameter tubular portion, and a taper portion connecting these portions. The ratio of the axial length of the conical tubular portion to the small diameter barrel portion is 2: 1 to
The second that reduces to a shape having a series as 1.8: 1.2
The second punch for performing the preliminary step and the taper portion on the end side of the blank formed in the second preliminary step are held down to form the annular collar portion by overhang molding, and the taper is formed on one end side of the annular collar portion. Par
Of the annular flange including a third preliminary step in which the conical cylindrical portion and the small diameter cylindrical portion are formed in series with the axial length ratio of 1: 2 to 0.7: 1.3. Forming a third punch for performing a step, forming a first cylindrical portion having a step portion perpendicular to the axial direction by holding down a conical cylindrical portion connected to one end side of the annular flange portion, and a tip portion from this step portion Up to the fourth punch for forming the first and second cylinders forming the second cylinder, and the fifth step for suppressing the tip end side of the second cylinder to form the annular protrusion. It consists of punches.

The first punch has a cylindrical tip portion having a round tip surface, a large diameter portion having a larger outer diameter than the tip portion and a diameter larger than the annular collar portion, and a taper surface connecting these portions. The second punch has an opening at the front surface of the external punch, a small diameter portion at the inner portion, and a hole portion having a taper surface connecting these portions, and a groove portion is provided in series between the small diameter portion and the inner punch. The ratio of the axial length of the hole and the groove is 2: 1.
1.8 to 1.2, the third punch is a taper for connecting the opening on the front surface of the external punch and the small diameter portion on the inner side to these.
A groove portion is formed in series with a small-diameter portion and an internal punch having a hole portion having a surface, and the axial length ratio of the hole portion and the groove portion is 1: 2 to 0.7: 1.3, The fourth punch has a hole portion for the outer punch and a series of groove portions for the small diameter portion and the inner punch, and the fifth punch has a cylindrical tip shaft portion projecting from the center of the front surface of the outer punch. It is preferable that the outer punch has an annular shallow groove on the peripheral surface of the front end shaft portion.

Further, according to the method of molding a connecting end portion of a pipe according to the present invention, an annular collar portion formed at a position apart from one end in the axial direction of the pipe material and having an outer diameter larger than that of the pipe material,
A first tubular portion formed at a position adjacent to the one end side in the axial direction of the annular collar portion and having an outer diameter smaller than that of the annular collar portion; and a position adjacent to one end side in the axial direction of the first tubular portion. A second formed with an outer diameter smaller than that of the first tubular portion
A tubular portion and an annular raised portion formed with an outer diameter smaller than the annular collar portion and larger than the second tubular portion at a position adjacent to the one end side in the axial direction of the second tubular portion. In the formation of the connecting end of the pipe, a first preliminary step of fixing the pipe material with a clamp and expanding one end in the axial direction of the pipe material and a portion in the vicinity thereof to form the relatively large-diameter cylindrical portion, A cone-shaped cylindrical portion having a large-diameter body portion that is connected to the taper portion on the raw pipe side formed in the first preliminary step, a small-diameter cylindrical portion, and a taper portion that connects them, and this cone body A second preliminary step of reducing the axial length ratio of the tubular portion and the small-diameter body portion to 2: 1 to 1.8: 1.2 in a continuous shape, and the element formed in the second preliminary step. The taper portion on the end side of the pipe is held down to form the annular collar portion by overhanging, and the taper shape is formed on one end side of the annular collar portion. A step of forming an annular collar portion including a third preliminary step in which the conical cylindrical portion and the small diameter cylindrical portion are formed in series with the axial length ratio being 1: 2 to 0.7: 1.3; Molding of a first tubular portion having a step portion perpendicular to the axial direction by suppressing a conical tubular portion connected to one end side of the annular collar portion, and a first tube forming a second tubular portion from the step portion to the tip end portion And a second tubular portion forming step, and an annular raised portion forming step in which the first tubular portion and the second tubular portion are fixed by an auxiliary clamp and the distal end side of the second tubular portion is held down to form an annular raised portion. Consists of.

The outer diameter expanded by the first forming punch is preferably larger than the groove of the clamp.
It is preferable that the outer diameter of the large-diameter body portion of the conical cylinder portion formed by the forming punch is substantially the same as the groove of the clamp.

[0010]

In the first molding step and the second molding step, the preliminary step is continuously performed, the annular collar portion is molded in the next third molding step, and the first cylinder portion and the second cylinder portion are molded in the fourth molding step. Molding the fifth
Since the annular ridge can be formed in the molding step, the connecting end of the pipe can be completed in as few as 5 steps. Then, after expanding the pipe in the first molding step, the second
~ Since each part is formed by successively reducing the diameter in the fifth forming step, it is possible to obtain the desired shape of each part without giving undue stress to the processed part in the forming step of each part, and breaking during processing. It is possible to provide a product having a high-strength connection end part that is protected from

[0011]

An embodiment will be described with reference to the drawings. As shown in FIG. 1, a connecting end 1a of a pipe 1 manufactured according to an embodiment of the present invention and a mating pipe 2 are connected by a union joint of a half union 3 and a union nut 4.

The half union 3 has an annular step portion 3a at a predetermined position of the inner cylinder, and the annular step portion 3a serves as a boundary,
Pipe 2 which is the other side from the base end toward the annular step 3a
Is attached and fixed integrally by brazing or the like, has a receiving portion 3b for receiving the connecting end portion 1a of the pipe 1 from the tip side toward the annular step portion 3a, and has a surface 3c chamfered at the tip. It is formed to have a threaded portion 3d on the outer circumference, and the union nut 4 can be screwed onto the threaded portion 3d from the surface 3c side.

The connecting end portion 1a of the pipe 1 has a tip surface 3c of the half union 3 and a small diameter portion 4 of the union nut 4.
It has a collar portion 5 sandwiched between a and a first cylinder portion 6 having an outer diameter smaller than that of the collar portion 5, and a first cylinder portion 6 on the front end side of the collar portion 5.
The second tubular portion 7 having a smaller diameter and the annular raised portion 8 having substantially the same diameter as that of the first tubular portion 6 are provided, and the first tubular portion 6 and the annular raised portion 8 receive the receiving portion 3b of the half union 3. The second cylindrical portion 7 has an outer diameter to be inserted therein, and a bottom portion of the second cylindrical portion 7 is formed between the first cylindrical portion 6 and the annular ridge portion 8 to form a concave groove for accommodating the O-ring 9.

2 to 9 are views showing a method of molding the connecting end portion of the pipe of FIG. This forming process depends on the beading process of the punch, and the forming process will be described below in the order of forming steps.

FIG. 2 is a front view showing a partial cross section of the clamp mechanism in a state in which the raw pipe forming the connecting end portion of the pipe is fixed. In FIG. 2, the clamp mechanism includes a first clamp portion 21 and a second clamp portion 22 that are overlapped with each other to form a circular groove 20 in the axial direction. Each clamp part 2
1 and 22 have grooves 21a and 22a provided along the circumference of the circular groove 20 on the end face. The raw pipe 10 has grooves 21a and 22a at the tip end portions for forming the connection end portion 1a.
It is made to project from the side of, and is sandwiched and fixed by the first and second clamps 21 and 22. First, the work of the raw pipe 10 is fixed by the clamps 21 and 22, and in the subsequent steps, the clamps 21 and 22 are not removed until the processing is completed.

FIG. 3 is a view showing the shape of a processed product after completion of the first molding step and a punch used in the first molding step. The first punch 30 includes a cylindrical tip portion 32 having a round tip surface 31, a large-diameter portion 33 having a larger outer diameter than the tip portion 32, and a taper surface 34 connecting these. . The raw pipe 10 is sandwiched between the clamps 21 and 22, and the first punch 30 presses the raw pipe 10 against the opening of the raw pipe 10 from the right side in the drawing to move the raw pipe 10 radially outwardly to the taper portion 11. Expand the pipe so that the outer diameter becomes D1. The outer diameter D1 is a pipe having a diameter larger than the grooves 21a and 22a of the clamps 21 and 22.

FIG. 4 is a view showing the shape of a processed product after completion of the second molding step and the shape of a punch used in the second molding step. The second punch 40 has an inner diameter D1 on the front surface of the outer punch 41. It has an opening 42, a small diameter portion 43 at the inner portion having an inner diameter of D2, and a hole portion 45 having a taper surface 44 connecting them, and the thickness y is formed by the inner diameter D2 of the small diameter portion 43 and the inner punch 46. It has a structure having a series of groove portions 47 having the above, and the axial length ratio of the hole portion 45 and the groove portion 47 is formed as hole portion: groove portion = 2: 1 to 1.8: 1.2. ing. Base pipe 10 expanded to the outer diameter D1 in the first molding process
The end portion of the second punch 40 is pressed by the second punch 40 to connect to the taper portion 11 formed in the first forming step, and the large-diameter body portion 12 having an outer diameter of D3 and the small-diameter portion having an outer diameter of D2 are connected. A conical cylindrical portion having a cylindrical portion 13 and a taper portion 14 connecting them, and a small-diameter cylindrical portion 13 are formed in series in the axial direction on the smaller diameter side of the conical cylindrical portion. The outer diameter D3 of the large-diameter body portion 12 is reduced and formed to be substantially the same as the groove 20 of the clamps 21 and 22. The first molding step and the second molding step are first and second preliminary molding steps for shaping the shape in the next step.

FIG. 5 is a diagram showing the shape of a processed product after completion of the third molding step and the shape of the punch used in the third molding step. The third punch 50 has an opening portion in which the inner diameter of the outer punch 51 is D4. 52 and a small-diameter portion 53 at the inner portion having an inner diameter of D2
And a hole portion 55 provided with a taper surface 54 connecting them.
And has an inner diameter D2 of the small diameter portion 53 and an inner punch 56.
And has a structure having a series of groove portions 57 having a thickness y, the inner diameter D4 of the opening portion 52 is larger than the outer diameter of the raw pipe 10 and smaller than the circular groove 20 on the end faces of the clamp portions 21 and 22, In addition, the hole 55 and the groove 57 of the third punch 50.
And the ratio of the length in the axial direction is as follows: hole portion: groove portion = 1: 2 to 0.
7: 1.3, the hole portion 55 of the third punch is substantially half the hole portion 45 of the second punch, and the groove portion 57 of the third punch is the second.
It is formed to be approximately twice as large as the groove portion 47 of the punch 40. The third punch 50 is pressed against the end portion of the raw tube 10 formed in the second forming step to perform the holding step. When the third punch 50 is pressed, a taper surface 54 which connects the opening 52 of the inner diameter D4 of the third punch 50 and the small diameter portion 53 of the inner diameter D2 of the end portion of the raw tube 10 formed in the second step is formed. When pressed against the taper portion 14, the end portion of the raw pipe 10 shown in FIG.
The collar portion 5 is pressed into the circular grooves 21a, 22a of the first and second clamps 22 so as to project into the circular grooves 21a, 22a.
Is formed on one end side in the axial direction of the above in a shape including a cone-shaped cylindrical portion to be the taper portion 15 and a small-diameter cylindrical portion 16 in series. The third molding step includes a step of molding the collar portion 5 and a preliminary step of molding the next first tubular portion 6.

FIG. 6 is a view showing the shape of the processed product after completion of the fourth molding step and the shape of the punch used in the fourth molding step. The fourth punch 60 has a hole 62 having an inner diameter D4 of an outer punch 61. The inner diameter D2 of the small-diameter portion 63 and the inner punch 64 have a series of groove portions 65 having a thickness y. The inner diameter D4 of the hole portion 62 of the outer punch 61 is smaller than the outer diameter of the annular collar portion 5 and larger than the outer diameter of the raw tube 10. In the third forming step, the fourth punch 60 is pressed against the end portion of the raw pipe 10 having the taper portion 15 and the small diameter tubular portion 16 having the outer diameter D2. As shown in FIG. 6, the end portion of the shell 10 shown in FIG. 5 has a first cylindrical portion 6 having a step portion 17 perpendicular to the axial direction from the taper portion 15, and an axial direction from the step portion 17. The second tubular portion 7 is formed to the tip side to the side. This fourth molding step
This is the process of forming the first tubular portion 6 and the second tubular portion 7.

FIG. 7 is a view showing an auxiliary clamp used in the beading process which is continuously performed in the fourth molding step. The auxiliary clamp 70 includes a first auxiliary clamp portion 71 and a second clamp portion 72, and has a first inner diameter that sandwiches the first cylinder portion 6 and the second cylinder portion 7 formed in the fourth molding step of FIG. The hole 73 has a surface 73, a second inner diameter surface 74, and a third inner diameter surface 75 having an inner diameter D4 provided along the periphery of the end surface of the second inner diameter surface 74. 4th
Subsequent to the molding step, the auxiliary clamp 70 is attached to the end portion of the raw pipe 10 when performing the beat attaching process in the next fifth molding step.

FIG. 8 is a view showing the shape of the processed product after the fifth forming step and the punch used in the fifth forming step. The fifth punch 80 has a cylindrical tip shaft portion 82 projecting from the center of the front surface of the external punch 81, and a structure having an annular shallow groove 83 on the peripheral surface of the tip shaft portion 82 on the front surface of the external punch 81. Become. In the fourth molding step, the auxiliary cylinder 70 sandwiches the second cylinder portion 7 having an outer diameter D2 continuously provided on one end side of the step portion 17 and the fifth punch 80 is pressed. When the end portion of the raw tube 10 is fitted into the groove 83 and pressed, the second
The third inner diameter surface 75 of the auxiliary clamp 70 is provided on the distal end side of the tubular portion 7.
The annular ridge portion 8 is formed adjacent to the second tubular portion 7 in the axial direction at one end side in the axial direction, and the O-ring 9 is provided at the bottom between the first tubular portion 6 and the annular ridge portion 8. By forming a groove to be mounted, the shape of the connecting end portion 1a of the pipe 1 shown in FIG. 9 is obtained.

[0022]

Since the present invention has the above-mentioned structure,
By adopting the beading process at the last step of the connecting end of the pipe, the number of steps can be reduced compared with the conventional one, and the end of the pipe suitable for mass production is easy. There is an advantage in that it is possible to provide a method of forming a pipe portion and a structure of a connecting end portion of a pipe having improved quality.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a connecting end portion of a pipe manufactured according to the present invention connected to a mating pipe by a union joint.

FIG. 2 is a cross-sectional view of a clamp that shows a fixed material.

FIG. 3 is a processed product and a first product in a state where the first molding process is completed.
It is sectional drawing which shows the shape of the punch used for a shaping | molding process.

FIG. 4 is a processed product and a second product in a state where the second molding process is completed.
It is sectional drawing which shows the shape of the punch used for a shaping | molding process.

FIG. 5 is a processed product and a third product after the third molding process is completed.
It is sectional drawing which shows the shape of the punch used for a shaping | molding process.

FIG. 6 is a processed product and a fourth product after the fourth molding process is completed.
It is sectional drawing which shows the shape of the punch used for a shaping | molding process.

FIG. 7 is a cross-sectional view of a clamp in which the first and second cylindrical portions of the processed product after the fourth molding step are fixed and shown.

FIG. 8 is a processed product and a fifth product after the fifth molding process is completed.
It is sectional drawing which shows the shape of the punch used for a shaping | molding process.

FIG. 9 is a front view showing a connection end portion of a pipe which has completed all molding steps.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 pipe 5 annular collar part 6 1st cylinder part 7 2nd cylinder part 8 annular ridge part 10 pipe material 11 taper part 12 large diameter body part 13 small diameter cylinder part 14 taper part 15 taper part 16 Small Diameter Cylindrical Section 17 Stepped Section 21 First Clamp 22 Second Clamp 30 First Punch 31 Tip Surface 32 Tip Section 33 Large Diameter Section 34 Taper Surface 40 Second Punch 41 External Punch 42 Opening 43 Small Diameter Section 44 Te -Par surface 45 Hole portion 46 Internal punch 47 Groove portion 50 Third punch 51 External punch 52 Opening portion 53 Small diameter portion 54 Taper surface 55 Hole portion 56 Internal punch 57 Groove portion 60 Fourth punch 61 External punch 62 Hole portion 63 Small diameter part 64 Internal punch 65 Groove part 70 Auxiliary clamp 80 Fifth punch 81 External punch 82 Tip shaft part 83 Groove

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area F16L 19/03 F16L 19/03 // B21D 53/06 B21D 53/06 A

Claims (3)

[Claims] 1. An annular collar portion formed with a larger outer diameter than the tubular material at a position distant from one axial end of the tubular material, and the annular collar at a position adjacent to the one axial end of the annular collar portion. First formed with an outer diameter smaller than the collar
A tubular part, a second tubular part formed at a position adjacent to the one axial end of the first tubular part with an outer diameter smaller than the first tubular part, and one axial end of the second tubular part In the formation of the connecting end portion of the pipe having an annular ridge portion having an outer diameter smaller than the annular collar portion and larger than the second tubular portion at a position adjacent to the side, the shaft of the pipe material is formed. A first punch that is subjected to a first preliminary step of expanding one end in the direction and a portion in the vicinity thereof to form the relatively large-diameter cylindrical portion;
A cone-shaped cylindrical portion having a large-diameter body portion and a small-diameter cylindrical portion connected to the taper portion on the raw pipe side formed in the preliminary step, and a taper portion connecting these, and the cone-shaped cylindrical portion. And a second punch that is subjected to a second preliminary step of reducing the diameter of the small-diameter body portion in a series having a ratio of the axial length of approximately 2: 1, and an end portion of the raw pipe formed in the second preliminary step. The taper portion on the side is pressed down to form the annular collar portion by overhanging, and the taper is attached to one end side of the annular collar portion.
In order to perform the press forming step on the annular collar portion including the third preliminary step in which the ratio of the axial length of the conical cylindrical portion and the small diameter cylindrical portion is approximately 1: 2 is formed in series. Molding of a third punch and a first tubular portion having a step portion perpendicular to the axial direction by holding down a conical tubular portion connected to one end side of the annular flange portion, and a second tubular portion from the step portion to the tip end portion. And a fifth punch for performing a forming step of the first and second tubular portions that form the groove, and a fifth punch for performing a restraining step of holding the tip end side of the second tubular portion to form an annular ridge. A device for molding a connecting end portion of a pipe, characterized by: 2. An annular collar portion formed with an outer diameter larger than that of the pipe material at a position away from one end of the pipe material in the axial direction, and the annular shape at a position adjacent to one end side in the axial direction of the annular flange portion. First formed with an outer diameter smaller than the collar
A tubular part, a second tubular part formed at a position adjacent to the one axial end of the first tubular part with an outer diameter smaller than the first tubular part, and one axial end of the second tubular part In the formation of the connecting end portion of the pipe having an annular ridge portion formed with an outer diameter smaller than the annular collar portion and larger than the second tubular portion at a position adjacent to the side, a round tip surface is formed. A first punch having a cylindrical tip portion, a large-diameter portion having a larger outer diameter than the tip portion and a diameter larger than the annular collar-shaped portion, and a taper surface connecting the first punch and the front surface of the outer punch. It has a hole portion having a small diameter portion at the opening and the inner portion and a taper surface connecting these portions, and also has a groove portion in series with the small diameter portion and the internal punch, and the groove portion in the axial direction of the hole portion and the groove portion. A second punch having a length ratio of about 2: 1 and a small diameter portion at the front opening and the back of the external punch. It has a hole portion having a taper surface for connecting them and forms a groove portion in series with a small diameter portion and an internal punch, and the ratio of the axial length of the hole portion to the groove portion is approximately 1: 2. A third punch, a fourth punch having a hole for the external punch and a series of grooves formed by a small-diameter portion and an internal punch, and a cylindrical tip shaft portion projecting to the front surface of the external punch, An apparatus for forming a connecting end portion of a pipe, comprising: a fifth punch having an annular shallow groove on a peripheral surface of a front end shaft portion of an external punch. 3. An annular collar portion formed with a larger outer diameter than the tubular material at a position distant from one axial end of the tubular material, and an annular collar at a position adjacent to the one axial end of the annular collar portion. First formed with an outer diameter smaller than the collar
A tubular part, a second tubular part formed at a position adjacent to the one axial end of the first tubular part with an outer diameter smaller than the first tubular part, and one axial end of the second tubular part In the formation of the connecting end portion of the pipe having an annular raised portion formed with an outer diameter smaller than the annular collar portion and larger than the second tubular portion at a position adjacent to the side, the pipe material is clamped. And the axially one end of the pipe material and its vicinity are expanded to form the relatively large-diameter cylindrical portion, and the raw tube side tape formed in the first preliminary process. Par
The diameter of the conical cylinder having a large-diameter body section connected to the section, a small-diameter cylinder section, and a taper section connecting them, and the ratio of the axial lengths of the conical cylinder section and the small-diameter cylinder section. A second preliminary step of reducing the diameter to a series having a ratio of approximately 2: 1 and a taper portion on the end side of the raw pipe formed in the second preliminary step are held down to form an annular collar portion by extension molding. A tape is attached to one end of the annular collar portion.
A step of forming an annular collar portion including a preliminary step of forming a second cylinder part in which the ratio of the axial length of the conical cylindrical part and the small diameter cylindrical part is approximately 1: 2. Forming a first tubular portion having a step portion perpendicular to the axial direction by suppressing a conical tubular portion connected to one end side of the annular collar portion, and forming a second tubular portion from the step portion to the tip end Molding step of the first tubular portion and the second tubular portion, and annular ridge portion forming in which the first tubular portion and the second tubular portion are fixed by an auxiliary clamp and the distal end side of the second tubular portion is held down to form an annular ridge portion. A method for molding a connecting end portion of a pipe, which comprises the steps of: