JPH04322831A - Diameter expansion method for metallic tube and synthetic resin lining metallic tube - Google Patents

Abstract

PURPOSE:To provide the diameter expansion method which can improve remarkably a service life of formed rubber, at the time of executing the diameter expansion of a metal tube and a synthetic resin lining metallic tube by a bulge forming method. CONSTITUTION:In a state that a seal ring 4 made of a synthetic resin, which has almost the same diameter as the inside diameter of a tube 2 to be subjected to diameter expansion, and is formed by a material being softer than hardness of the inner wall surface of the tube is allowed to run along the end face of formed rubber 3, and also, a metallic washer 5 whose diameter is smaller than that of the seal ring is allowed to run along the outside of the seal ring 4, pressure is applied to the forming rubber 3 through the washer 5 and the seal ring 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method for expanding the diameter of metal tubes and synthetic resin-lined metal tubes using a rubber bulge forming method.

0002

[Prior Art] For example, composite pipes in which the inner circumferential surface of a metal pipe is lined with a synthetic resin layer are used for drainage pipes installed vertically in buildings. To connect them, generally, a socket is formed at the end of one of the composite pipes to be connected, and a rubber packing, for example, is attached to this socket, and the end of the other composite pipe is inserted into the socket. The connection is made by inserting the opening into this packing.

[0003] Incidentally, the socket portion of a composite pipe is formed by enlarging the diameter of the end of the composite pipe using a rubber bulge forming method as disclosed in, for example, JP-A-2-11233 and JP-A-2-130126. It is now possible to do so.

That is, as shown in FIG. 5, a metal washer 62 provided at the tip of a cylinder rod 61 and a molded rubber 63 attached to the cylinder rod 61 are expanded in diameter to form a socket. The tube 64 is inserted from the tube end, and the mold 65 is placed over the tube end from the outside. Note that this mold 65 has a recess 66 formed therein having an inner surface shape that follows the outer surface shape of the socket, and two
It is split into two.

Next, as shown in FIG. 6, the molded rubber 63 is compressed through the washer 62 by pulling the cylinder rod 61 toward the tube end. By this compression, the molded rubber 62
The longitudinal dimension tends to shrink and the width direction expands, and the pressure causes the end of the tube 64 to deform to follow the internal shape of the recess 66 of the mold 65, forming a socket 64a at the tube end. It is supposed to be done.

[0006]

[Problems to be Solved by the Invention] However, in the above-described conventional method for expanding the diameter of a tube using the rubber bulge forming method, the washer 62
When compressing the molded rubber 63, there is a risk that if the rubber comes into contact with the synthetic resin running layer or plating layer formed on the inner wall surface of the pipe for the purpose of preventing corrosion, the lining layer or plating layer may be damaged and their function may be inhibited. The diameter of the washer 62 is made slightly smaller than the inner diameter of the tube 64 so that the washer 62 does not come into contact with the lining layer or the plating layer.

Therefore, as the molded rubber 63 is compressed, the washer 62 does not touch the inner wall surface of the pipe, but as shown in FIG.
As shown in the figure, a gap 67 is formed between the washer 62 and the mold 65, so a part 63a of the molded rubber 63 protrudes into this gap 67, and the ends of the molded rubber 63 are easily damaged and have a short lifespan. I have a problem to say.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a method for expanding the diameter of metal tubes and synthetic resin-lined metal tubes in which molded rubber is less likely to be damaged.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for expanding the diameter of a metal tube and a synthetic resin-lined metal tube on the end face of the molded rubber when expanding the diameter of the metal tube using a rubber bulge molding method. A synthetic resin seal ring made of a material that has approximately the same diameter as the inner diameter of the pipe and is softer than the inner wall surface of the pipe is placed along it, and a metal washer with a smaller diameter than the seal ring is placed on the outside of this seal ring. The gist of this paper is a method for expanding the diameter of metal tubes and synthetic resin-lined metal tubes, which is characterized by applying pressure to molded rubber through a washer and the seal ring.

0010

[Operation] According to the above structure, the outer circumferential surface of the seal ring is arranged in close contact with the inner circumferential surface of the pipe, and when the molded rubber is compressed through the washer and the seal ring, the seal ring is also compressed and the outer circumferential surface of the pipe is compressed. The diameter becomes larger and it comes to be in complete contact with the inner circumferential surface of the pipe. Therefore, the gap in which the molded rubber tends to protrude due to compression is completely closed.

Furthermore, the seal ring receives the repulsive force of the molded rubber in the direction of the washer due to compression, but the washer can completely absorb this force.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to the drawings showing embodiments thereof.

FIGS. 1 and 2 show a method for expanding the diameter of the intermediate portion of a pipe, which is an embodiment of the method for expanding the diameter of a metal pipe and a synthetic resin-lined metal pipe according to the present invention. The steps will be explained in detail.

[0014] As shown in FIG. 1, a mold 1 having a recess 11 that follows the outer shape of the expanded diameter portion is prepared, and the pipe 2 whose diameter is to be expanded is inserted into the mold 1. Note that the mold 1 may be split into two in the axial direction and the split molds may be combined to cover the outside of the tube 2 with the mold 1.

(2) Insert the molded rubber 3 into the tube 2, and place the seal ring 4 and washer 5 along both end faces of the molded rubber 3. In addition,
It is preferable to integrate the seal ring 4 and washer 5 in advance.

■ As shown in FIG. 2, pressure is applied to the molded rubber 3 from the outside via the washer 5 and the seal ring 4 to compress the molded rubber 3. Note that pressure can be applied, for example, by connecting cylinder rods to the washers 5 on both sides and pushing the cylinder rods toward the recesses 11, respectively.

Due to this compression, the molded rubber 3 contracts in the longitudinal direction and tends to swell at the center, and the tube 2 is deformed along the recess 11 due to the pressure. Also, seal ring 4
When pressure is applied, the tube is compressed and its outer diameter becomes slightly larger, so that the inner circumferential surface of the pipe and the outer circumferential surface of the seal ring are brought into closer contact with each other. Therefore, there is no gap between the seal ring 4 and the tube 2, and it is possible to completely prevent the molded rubber 3 from protruding outward. Synthetic resin-lined metal tubes are particularly effective in expanding the diameter of lined metal tubes because their inner diameters vary more widely than metal tubes.

Moreover, since the seal ring 4 is supported by the washer 5, it is prevented from deforming outward even when the repulsive force of the molded rubber 3 is applied, and a stable state of close contact can always be obtained.

The seal ring 4 used in the diameter expansion method described above is
For example, the material includes nylon such as MC nylon (monomer casting nylon), synthetic resin such as high-density polyethylene, and polyvinyl chloride.
When expanding the diameter of a synthetic resin-lined metal pipe, it is preferable to use a material that is less hard than the lining resin, and its outer diameter should be approximately the same as or slightly larger than the maximum inner diameter of the pipe 2 whose diameter is to be expanded. is preferred.

Furthermore, as shown in FIG. 3, the peripheral portion 41
It is particularly preferable to make the wall a little thick so that it protrudes toward the molded rubber 3 side. That is, if the seal ring 4 having such a shape is used, when the molded rubber 3 is compressed, the peripheral edge 41 of the seal ring 4 will be compressed due to the repulsive force of the molded rubber 3.
is bent toward the washer 5 as shown by the chain line in FIG. 3, and the outer diameter of the seal ring 4 becomes larger. Therefore, there is an advantage that the seal ring 4 can be brought into tighter contact with the inner wall surface of the pipe.

The material of the metal tube whose diameter can be expanded by this diameter expansion method is not limited to steel, but also soft iron, copper, aluminum,
Examples include lead. In addition, as the resin constituting the lining layer of a synthetic resin-lined metal pipe, it is effective to use a resin that has an elongation of 20% or more at room temperature to prevent cracks from occurring during diameter expansion. Specifically, polyvinyl chloride , polyethylene, crosslinked polyethylene, polybutene, polypropylene,
Examples include fluororesin.

The lining layer is not particularly limited, but can be formed, for example, by inserting a synthetic resin pipe into a metal pipe and integrating it with the metal pipe via an adhesive. Moreover, as the adhesive, rubber-based, epoxy-based, hot melt-based adhesives, and the like are preferable.

[0023] Below, one of the implemented examples and comparative examples is shown.
Explain an example.

[0024]

[Example 1] Molded rubber made of urethane rubber, average diameter is 11
A seal ring made of MC nylon with an outer diameter of 109.5 mm and a thickness of 10 mm.
Using a washer made of 0 mm S45C (iron), the wall thickness of the steel pipe is 2.0 mm and the wall thickness of the PVC lining pipe is 1.0 mm.
mm, average inner diameter is 110.0mm, minimum inner diameter is 10
9.7mm lining pipe with outer diameter of 116.0mm
When the diameter was expanded to 140.0 mm by the bulge molding method shown in FIGS. 1 and 2, there was almost no damage to the ends of the molded rubber even after 500 shots of molding.

[0025]

[Comparative Example 1] When the diameter was expanded in the same manner as in Example 1 with the washer 5 placed directly along the molded rubber 3 without using the seal ring 4, as shown in FIG. At times, there is a gap 22 between the washer 5 and the tube 2, and a part 33 of the molded rubber 3 enters this gap 22, so the end face of the molded rubber is damaged all around after 50 shots, causing the tube to expand into the specified shape. I can no longer measure the diameter.

[0026] It is clearly seen from Example 1 and Comparative Example 1 that the life of molded rubber can be dramatically improved by using the diameter expanding method according to the present invention. Note that the method for expanding the diameter of metal tubes and synthetic resin-lined metal tubes according to the present invention is not limited to expanding the diameter of the central portion of the tube as in the above embodiments, but is also applicable to 2-1
Similar to Japanese Patent No. 30126, it can also be applied to forming a socket at the end of a tube.

[0027]

[Effects of the Invention] The method for expanding the diameter of metal tubes and synthetic resin-lined metal tubes according to the present invention is configured as described above, so that when the molded rubber is compressed through the washer and the seal ring, the seal The ring is also compressed, increasing its outer diameter and coming into close contact with the inner circumferential surface of the pipe. In addition, the seal ring receives the repulsive force of the molded rubber in the direction of the washer due to compression, but since this force can be completely absorbed by the washer, the seal ring does not bend, making the adhesion more stable. be able to.

[0028] Therefore, the ends of the molded rubber are prevented from protruding, the ends of the molded rubber are not damaged by the compression operation, the life of the molded rubber is dramatically improved, and manufacturing costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a state before diameter expansion of a metal tube and a synthetic resin-lined metal tube diameter expansion method according to the present invention.

FIG. 2 is a sectional view showing the expanded state.

FIG. 3 is a sectional view showing a preferable example of the seal ring.

FIG. 4 is a sectional view showing a state in which molded rubber is compressed using only a washer, excluding a seal ring.

FIG. 5 is a cross-sectional view showing a state before diameter expansion in a conventional diameter expansion method for metal tubes and synthetic resin-lined metal tubes.

FIG. 6 is a sectional view showing the expanded state.

[Explanation of symbols]

2 pipe 3 Molded rubber 4 Seal ring 5 Washer 62 Washer 63 Molded rubber 64 pipe

Claims (1)

[Claims] [Claim 1] Metal tube and synthetic resin lining When expanding the diameter of a metal tube using the rubber bulge molding method, the end surface of the molded rubber is formed of a material that has approximately the same diameter as the inner diameter of the tube to be expanded and is softer than the hardness of the inner wall surface of the tube. At the same time, a metal washer with a smaller diameter than the seal ring is placed along the outside of this seal ring, and pressure is applied to the molded rubber through this metal washer and the seal ring. A method for expanding the diameter of metal pipes and synthetic resin-lined metal pipes.