JPS6154992B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flexible tube whose inner surface is coated with a corrosion-resistant resin coating.

Conventionally, flexible tubes have been employed when joining two pipes with some flexibility in their positional relationship. For example, as shown in Figure 1,
When connecting the fire prevention sprinkler 7 installed on the ceiling 9 of a building to the pipe 6 branched from the water main pipe 8, in order to facilitate their positioning,
A flexible tube 1 is used. but,
This flexible tube had the disadvantage that since its inner surface was in direct contact with the fluid, corrosion progressed gradually, leading to damage. For example, if the above-mentioned flexible tube 1 is damaged due to corrosion, the water pressure inside the sprinkler will temporarily decrease, which will activate the pump installed upstream of the water main pipe 8, causing the sprinkler 7 to malfunction. .

As a countermeasure to this problem, there is a proposal to apply a resin coating to the inner surface of the flexible tube to improve chemical resistance and corrosion resistance. There are two types of coating: one that forms a coating that adheres closely to the inner surface of the bellows-shaped flexible tube, and one that does not adhere to the inner surface and contacts only the corrugated bottom of the flexible tube.
255). The former is one in which a coating is formed by spin coating a molten fluorine resin on the inner surface of a flexible tube after molding. In this case, it is difficult to form a coating film of uniform thickness, and the continuous coating often results in an overall thick coating film. Since this thick coating film is adhered to the inner surface of the flexible tube, it reduces the flexibility of the flexible tube. Also,
There is also the possibility that pinholes may exist in the coating, resulting in poor reliability. On the other hand, in the latter case, as shown in FIG.
3 was inserted.

Therefore, a film of uniform thickness can be formed, and pinholes are less likely to exist in the film. However, between the flexible tube 2 and the fluorine resin tube 33, ring-shaped spaces 31 are formed at approximately equal intervals.
Because of the presence of As a result, a fluororesin tube with a large wall thickness is required, which reduces the flexibility of the flexible tube.

The present invention was made in view of these known tubes, and aims to eliminate the above-mentioned drawbacks and provide an easy method for manufacturing a flexible tube with good reliability and flexibility.

The structure of the inner-coated flexible tube is that the inner-coated flexible tube has a corrosion-resistant resin coating 3 applied to the entire inner surface of a metal flexible tube 2, and the resin coating 3 has a thin and substantially uniform thickness without pinholes. It is characterized in that it is a continuous film, is in close contact with the inner surface of the flexible tube, but is not bonded, and has almost no space between the flexible tube and the resin coating.

In the method for manufacturing the inner-coated flexible tube, a thin corrosion-resistant resin tube is inserted into a metal flexible tube in which large folds are formed around the circumferential surface at approximately equal intervals in the axial direction.

The metal flexible tube has a slightly larger pleat pitch than the finished flexible tube.

The feature is that internal pressure is applied to the corrosion-resistant resin tube by a high-temperature fluid to cause the resin tube to bulge along the inner surface of the metal flexible tube, and then the flexible tube is compressed in the axial direction until it reaches a predetermined pleat pitch. shall be.

(Operation of the present invention) When the inner-coated flexible tube is bent, the bellows portion of the metal flexible tube 2 contracts or expands and is plastically deformed. At this time, the resin coating is not bonded to the inner surface of the flexible tube, so the relative Moreover, since the coating has a uniform thickness and is thin, it is easily deformed while maintaining close contact with the flexible tube.

In actual use, even if a large internal pressure is applied, the coating is merely pressed against the inner surface of the tube, and compressive stress is exerted thereon. Therefore, rupture due to internal pressure does not occur.

In the method for manufacturing an inner-coated flexible tube according to the present invention, a corrosion-resistant resin tube 30 having a thin and uniform thickness and smooth inner and outer surfaces is provided.
is heated and softened by coming into contact with high-temperature, high-pressure fluid, and at the same time is pressed against the inner surface of the semi-finished flexible tube 20, deforming into a bellows shape, and coming into close contact with the inner surface without any gaps. At this time, since the folds of the flexible tube 20 have a relatively large pitch and only exhibit a gentle waveform, the thickness of the resin tube 30 does not change significantly locally, and the tube bulges when bulged by the high-pressure fluid. There is no risk that 30 will explode. Furthermore, since an originally intact resin tube is used, there is no damage to the resin coating 3 after hydraulic molding.

The flexible tube 20 as a semi-finished product coated with the above resin coating is then compressed in the axial direction, so that it contracts uniformly without buckling. At this time, the resin coating 3 on the inner surface of the flexible tube 2
0, and there is almost no change in thickness.

(Special Effects) The internally coated flexible tube has sufficient flexibility because the resin coating 3 on the internal surface is thin and has a uniform thickness and is not bonded to the internal surface of the flexible tube 2. Furthermore, the resin coating 3 does not burst due to internal pressure and has no scratches such as pinholes, so it has high reliability.

Further, according to the method for manufacturing an inner-coated flexible tube according to the present invention, a desired flexible tube can be easily manufactured as described below. That is, the flexible tube 20 as a semi-finished product having a relatively large pleat pitch can be easily manufactured by conventional techniques such as hydraulic molding or roller molding, and the thin-walled resin tube 30 can be easily manufactured. It's easy. Furthermore, resin tube 3
It is possible to supply high temperature and high pressure liquid into the flexible tube 20 into which the tube 20 is inserted by using a combination of a liquid pump and a heater, and compression processing in the final step is also a well-known technique. In this manufacturing method, a flexible tube 2 is produced as a semi-finished product having a relatively large pleat pitch by hydroforming a resin tube.
0 and then compresses the flexible tube 20 in the axial direction to form a predetermined pleat pitch. When the membrane 30 is expanded, a membrane of uniform thickness is formed without strain, and the membrane does not rupture. At the stage of hydroforming, the air existing between the flexible tube and the resin tube is easily discharged, so the closeness of the resin coating to the flexible tube is extremely high.

The present invention will be specifically described below based on embodiments shown in the drawings.

FIG. 2 shows an embodiment of an internally coated flexible tube. A corrosion-resistant resin coating 3 is provided closely on the inner surface of the metal flexible tube 2, but is not adhered to it.

The flexible tube 2 is preferably made of stainless steel to enhance corrosion resistance. Furthermore, fluororesin is suitable for the corrosion-resistant resin coating 3. The thickness of the coating is approximately 0.45 mm to 0.6 mm,
It is thinner than films made by conventional methods, and there is almost no unevenness in thickness. A blade 14 for protecting the flexible tube is fixed to the outer periphery of the flexible tube. A pair of cylindrical bodies 11, 11 are fitted on both ends of the flexible tube,
Nuts 12, 12 for connecting to other pipes are rotatably locked to the cylindrical body, respectively.

FIGS. 3 and 4 show an embodiment of a series of steps for manufacturing the above-mentioned internally coated flexible tube.

First, the diameter is approximately 22 mm to 30 mm as shown in Figure 3.
A stainless steel flexible tube 20 having a total length of approximately 50 cm and a pleat pitch of approximately 9 mm is manufactured by a hydroforming method or the like. However, the flexible tube 2
0 is compression molded in the subsequent process and is approximately two-thirds
The folds become tight.

Next, the outer diameter of the flexible tube 20 is approximately
Fluorine resin tube 30 with a diameter of 22 mm and a thickness of approximately 0.5 mm.
is inserted, and then the resin tube is hydraulically molded along the inner surface of the flexible tube 20 using a device as shown in FIG. 4a. To do this, first, the cylindrical bodies 11, 1 are fixed to both ends of the flexible tube 20.
1 is housed and held from above and below by support members 42 and 43 having a split structure. Next, the closing members 46, 44
The round shaft parts 51, 51 of the flexible tube 20
Fits liquid-tightly into both openings. One of the closing members 46 is fixed, and is provided with a supply hole 52 for guiding high pressure oil supplied from an oil pump 47 into the tube. The oil pump 47 is supplied with oil at about 120° C. to 200° C. from the oil storage tank 54. A relief hole 53 is provided in the other closing member 44 and is connected to one stop valve 50. The outer surface of the closing member 44 is pressed by a press machine 45.
is pressed with a relatively weak force. In this state, the stop valve 50 is slightly opened and the pump 47 is started. When the oil flowing into the resin tube 30 exhausts the air inside the tube and the tube is filled with oil, the stop valve 5 is opened.
0 is fully closed and an internal pressure of about 75 to 80 kg/cm ² is applied inside the tube. By this, the resin tube 3
0 is softened by heat received from the high-temperature, high-pressure oil and is simultaneously hydrostatically formed on the inner surface of the flexible tube.
The resin tube 30 is also bulged in the vicinity of both end surfaces of the flexible tube as shown. As a final step, the flexible tube 20 is compression molded until the pleat pitch is about 6 mm. First of all, stop valve 50
is slightly opened to release the internal pressure, and then the press machine 45 is operated. As shown in FIG. 4, a group of guide members 41 are arranged in the pleats of the flexible tube 20 in contact with the recesses of the pleats in order to prevent buckling and local deformation during compression molding. There is. The press machine 45 presses the flexible tubes 2 until the guide members 41 are pressed together as shown in FIG. 4b.
Compress 0. However, the guide member 41 has the same thickness as the pleat pitch of the flexible tube 2 as a product.

The unnecessary parts of the resin tube 3 that protrude from both end faces of the flexible tube 2 are bulge-molded parts 1 near both end faces of the flexible tube 2.
It is cut leaving only 3 and 13. The bulging molded parts 13, 13 in the cross section are pushed and expanded along the flexible tube flange.

Incidentally, during hydroforming, if a through hole 49 is provided in one of the support members 42 as shown in FIG. ,
The resin tube adheres more tightly to the flexible tube. However, even without this mechanism,
Since the resin tube adheres substantially tightly to the inner surface of the flexible tube, there is no practical problem.

As described above, the inner-coated flexible tube has sufficient flexibility and reliability, and can be easily manufactured by the above-described method. Furthermore, the above method has the advantage that pinholes in the resin tube can be detected at the stage of hydroforming. The process is also more efficient than the conventional spin coating method. Furthermore, this resin coating can be made thinner than coatings made by conventional methods, so it is advantageous in terms of cost.

[Brief explanation of the drawing]

Fig. 1 is a front view of an example in which an inner-coated flexible tube is applied to a sprinkler connection, Fig. 2 is a partial cross-sectional view of an embodiment of an inner-coated flexible tube, and Figs. 3 and 4 a and b show the flexible tube. FIG. 5 is a partial sectional view of a conventional example. 2... Metal flexible tube, 3... Corrosion-resistant resin coating, 20... Flexible tube as a semi-finished product, 30... Corrosion-resistant resin tube,
41... Guide member, 42, 43... Support member, 4
4, 46...Closing member, 45...Press machine, 4
7, 48...pump, 50...stop valve,
51...Round shaft part.

Claims (1)

[Scope of Claims] 1. A step of penetrating a thin corrosion-resistant resin tube into a metal flexible tube in which large folds surrounding the circumference are formed at approximately equal intervals in the axial direction. A process of inserting a thin corrosion-resistant resin tube into the corrosion-resistant resin tube by applying high-temperature and high-pressure fluid to the corrosion-resistant resin. A step in which the tube is heated and softened while applying internal pressure to swell the resin tube along the inner surface of the metal flexible tube.A step in which the metal flexible tube and resin tube are compressed in the axial direction to shorten the pleat pitch. A method for producing an inner-coated flexible tube, the method being carried out in a series.