JPS5828104B2 - Manufacturing method of bellows tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a tubular body having a bellows structure.

When it is necessary to form an L-shape or a curved shape with a small radius of curvature at the joint part of a transport pipe for chemicals, water, or various gases, a bellows pipe 1 having the structure shown in Fig. 1 is used.
is often used.

This bellows tube is conventionally manufactured by inserting a tubular body made of thermoplastic plastic into a mold that has a bellows structure formed on its inner surface, heating the tubular body, and applying pressure from inside to press it against the inner surface of the mold. Alternatively, in the case of obtaining a metal bellows tube, it is manufactured by a method in which each unit of the bellows structure to be formed is sequentially heated and pressed using a mold similar to the above-mentioned mold and drawn.

However, in the former method, a mold must be prepared each time according to the dimensions of the desired bellows tube, and it is extremely difficult to easily manufacture a bellows tube with the desired dimensions, and the mold is expensive. The problem is that the resulting bellows tube is also very expensive, and the latter method involves forming the bellows structure unit by unit, which is extremely inefficient and cannot be manufactured at the site of use. Moreover, there is a problem that the resulting bellows tube lacks flexibility, and the current situation is that neither of them is satisfactory.

The present invention has been made for the purpose of solving the above-mentioned problems of the conventional method at once, and to easily provide a bellows tube, and especially to easily provide a bellows tube of a desired size at the site of use.

That is, in the present invention, regulating devices capable of regulating the thermal expansion of predetermined portions of the material tube are arranged at predetermined intervals on the outer circumferential surface of a material tube made of an organic polymer material and having thermal expansion properties, and then the material tube is The method is characterized in that the non-restricted portion of the material tube between the restrictors is heated to an appropriate temperature for thermal expansion and then cooled.

The material tube used in the present invention is made by adding additives such as a vulcanizing agent, an anti-aging agent, and a pigment to an organic polymer material, that is, natural rubber, synthetic leather rubber, thermoplastic plastic, or a mixture thereof, according to a predetermined method. A material tube is formed by forming it into a tubular shape, and the material tube is given the property of being able to expand its diameter by heating.
(thermal expandability).

Thermal expandability can be imparted to the material tube by heating the material tube to its softening point or melting point, stretching it in the axial direction to reduce its diameter, and then cooling it directly, or by heating the material tube to the above temperature range. Thereafter, the tube is passed through a core having a diameter smaller than that of the material tube to reduce its diameter.

In addition, the regulating devices are placed at predetermined intervals on the outer circumferential surface of the material tube to regulate the thermal expansion of predetermined portions of the material tube, ensuring heat resistance that will not be damaged by heating during thermal expansion work. Constructed of materials with

A specific example of this is a ring or a plate-shaped body made of metal, ceramics, asbestos, plastic, etc., and having an inner diameter slightly larger than the outer diameter of the material pipe, or a hollowed part having a diameter slightly larger than the outer diameter of the material pipe. Examples include those with .

It is preferable that the restricting device has a split structure as shown in FIG. 4, for example, since the restricting device can be easily removed from the outer circumferential surface of the material tube.

In the present invention, first, restrictors are placed at predetermined intervals on the outer peripheral surface of the material tube.

At this time, if a mold release agent such as silicone resin is applied to the outer peripheral surface of the material tube or the contact area of the restrictor with the material tube,
This is preferable because the phenomenon of sticking of the softened or melted material pipe and the restrictor does not occur during the thermal expansion work of the material pipe.

In the present invention, the material tube is then heated to an appropriate temperature for thermal expansion (softening point or melting point), and between the restricting tools (unrestricted portion of the material tube)
is thermally expanded.

The thermal expansion work can be carried out by placing the whole in a heating furnace and thermally expanding each non-regulated part at the same time, or by sequentially heating each non-regulated part with a heating device such as a gas burner or hot air gun to thermally expand each part individually. This is done by

The restriction is usually removed after the thermal expansion operation, but if the bellows tube is required to have pressure resistance, the restriction may be left as is.

The present invention is configured as described above, and has advantages such as being able to easily manufacture a bellows tube with simple operations, allowing manufacture at the site of use, and requiring no special mold.

Hereinafter, the present invention will be explained in more detail by way of examples with reference to the drawings.

Exception: After heating a polytetrafluoroethylene material tube with a diameter of 20 m and an inner diameter of 177 nm and a length of 700 mm in a 3400C heating furnace for 15 minutes, it was taken out of the heating furnace and immediately grasped at both ends and stretched to a length of 1750 mm. , cooled by immersing it in 20℃ water for 10 minutes, and the outer diameter was 14 mm.
A thermally expandable material tube 2 having an inner diameter of 12 mm was obtained.

Next, as shown in FIG.
r/LrLr
0m7rL, inner diameter 14.2m>width 5mm restrictor 3 is arranged.

Note that 4 is a non-restricted portion of the material tube 2. Thereafter, the areas between the regulating devices 3 are sequentially heated with a gas burner to thermally expand the non-limiting portions 4 of the material tube 2, and air (temperature 20° C.) is further blown thereto for cooling.

FIG. 3 shows the state after the above-mentioned cooling, and then the restrictor 3 is removed and the length is approximately 22 mm with straight portions 5 at both ends.
A bellows tube of 01n71L was obtained.

The outer diameter of the thermal expansion section 6 of the bellows tube is 19.5 mm.
Met.

As shown in FIG. 4, the restrictor 3 is made of half-moon-shaped asbestos bodies 7 and 8 connected by a pin 9 into a nongangular shape, and has a structure that can be divided into two parts.

The obtained bellows tube had the property of being able to be bent to a radius of curvature of 50 mm.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an example of a bellows tube, and FIGS. 2 and 3 show an example of the manufacturing method of the present invention.
The figure is a perspective view showing a state in which a restrictor is placed on the outer circumferential surface of a material tube, FIG. 3 is a vertical cross-sectional view showing a state after the non-restricting part of the material tube is expanded and cooled, and FIG. 4 is an embodiment. FIG. 2...Material pipe, 3...Regulating tool, 4...
...Non-regulated section.

Claims (1)

[Claims] 1. On the outer circumferential surface of a material tube made of an organic polymeric material and having thermal expansion properties, regulating devices capable of regulating the thermal expansion of predetermined portions of the material tube are placed at predetermined intervals, and then the material tube is heated to an appropriate temperature for thermal expansion. A method for manufacturing a bellows tube, which comprises heating the material to thermally expand the non-restricted portion of the tube, and then cooling the material.