JPH0220324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a reinforced pipe with different diameters in which a portion of a raw pipe is reduced in diameter.

[Conventional technology]

Stress is concentrated at the stepped portion due to the diameter difference in pipes of different diameters, so it may be necessary to reinforce this portion.

Conventionally, in order to reinforce such a stepped portion, a reinforcing ring C of an appropriate length is fitted onto the inner surface (or outer surface) of the stepped portion B of the tube body A, as shown in Fig. 1. The substantial wall thickness of part B was increased.

[Problem that the invention seeks to solve]

Since it is extremely difficult to bring the entire circumferential surface of the reinforcing ring C as described above into proper contact with the inner surface of the tube body A,
Even if the two were fixed by spot welding or the like, it would be difficult to obtain the desired strength, and furthermore, the processing would require considerable effort.

An object of the present invention is to provide a method for manufacturing a reinforced pipe with different diameters that can eliminate such problems.

[Means for solving problems]

According to the present invention, the above object is achieved by comprising the following steps.

(a) By slightly expanding the diameter of the raw pipe from the key point to the end, a small step is formed at the key point.

(b) Insert a reinforcing pipe with a diameter slightly smaller than the inner diameter of the expanded diameter part and slightly larger than the original diameter of the raw pipe from the end of the enlarged diameter part, and lock the inner end to the stepped part. let

(c) The enlarged diameter part of the raw pipe is reduced in diameter until it almost returns to its original diameter, and its inner surface is compressed against the entire outer peripheral surface of the reinforcing pipe.

(d) By swaging from the outer surface of the base pipe to the other end and reducing the diameter of this part, steps are formed at key points of the base pipe and the reinforcing pipe that are in close contact with each other. .

[Operation] A part of the material is once expanded in diameter, a reinforcing tube is inserted into this part, and the reinforcing tube is positioned against the expanded diameter step, and then the expanded diameter part is reduced in diameter to join the two, Furthermore, by forming diameter-reducing steps at key points, the connection between the two is made stronger and the diameter-reducing step is reinforced.

〔Example〕

First, as shown in FIG. 2, by slightly expanding the diameter 2 of the raw pipe 1 from a key point to one end, a small diameter-enlarging step 3 is formed at the key point.

Next, as shown in FIG. 3, from the end of the enlarged diameter section 2, a diameter slightly smaller than the inner diameter of the enlarged diameter section 2, a diameter slightly larger than the original inner diameter of the blank pipe 1, and a required length is obtained. The reinforcing tube 4 having the reinforcing tube 4 is inserted, and its inner end 4a is locked to the enlarged diameter stepped portion 3.

Then, by ironing or the like, the enlarged diameter part 2 of the raw pipe 1 is reduced in diameter to almost its original diameter, and its inner surface is tightened to the entire outer peripheral surface of the reinforcing pipe 2, as shown in FIG. Pressure is applied to securely fix the reinforcing tube 2 at the required position.

At the same time or after this, by swaging the outer surface of the raw pipe 1, including the portion that overlaps with the reinforcing pipe, as shown in FIG. A diameter-reduced step portion 5 having a diameter difference of .

As a result, the stepped portion 6 is attached to the reinforcing pipe 4 while remaining in close contact with the inner surface of the base pipe 1, and the two become a completely integrated double pipe with no gaps, and are reinforced as required. This results in pipes with different diameters.

If necessary, both tubes 1 and 4 may be fixed by spot welding, or key points of the raw tube 1 may be heated and processed.

〔Effect of the invention〕

According to the present invention, the reinforcing pipe inserted into the inner surface of the raw pipe can be brought into close contact with the raw pipe very easily and reliably, and at the same time can be brought into close contact with the raw pipe and made integral with it. At the same time, it is possible to form required diameter-reducing step portions whose inner surfaces are effectively reinforced at key points of the blank pipe.

The diameter of the large diameter portion of the completed different diameter pipe is almost the same as the diameter of the base pipe.

Moreover, since the diameter of the main part of the raw pipe is enlarged, insertion of the reinforcing pipe is easy.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view illustrating the steps for reinforcing the stepped portion in a conventional reinforced pipe with different diameters, and FIGS. 2 to 4 are
Embodiments of the present invention are shown, and FIG. 2 is a longitudinal sectional front view showing a state in which the diameter of the raw pipe is slightly expanded from a key point to one end, and FIG. 3 is a main part of the expanded diameter portion of the raw pipe. In place,
FIG. 4 is a longitudinal front view showing a state in which the reinforcing pipe is inserted, and FIG. teeth,
FIG. 4 is a longitudinal sectional front view showing a state in which a diameter-reducing step portion is attached from the state shown in FIG. 4; DESCRIPTION OF SYMBOLS 1... Base pipe, 2... Expanded diameter part, 3... Expanded diameter step part, 4... Reinforcement pipe, 4a... Inner end, 5... Reduced diameter step part.

Claims (1)

[Claims] 1. A method for manufacturing a reinforced pipe with different diameters, which comprises the following steps. (a) By slightly expanding the diameter of the raw pipe from a key point to one end, a small step is formed at the key point. (b) Insert a reinforcing pipe with a diameter slightly smaller than the inner diameter of the expanded diameter part and slightly larger than the original diameter of the raw pipe from the end of the enlarged diameter part, and lock the inner end to the stepped part. let (c) The enlarged diameter part of the raw pipe is reduced in diameter until it almost returns to its original diameter, and its inner surface is compressed against the entire outer peripheral surface of the reinforcing pipe. (d) By swaging from the outer surface of the base pipe to the other end and reducing the diameter of this part, steps are formed at key points of the base pipe and the reinforcing pipe that are in close contact with each other. .