JPH0671735A - Hose manufacturing method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a hose manufacturing method capable of obtaining a hose which does not require cutting of a bag-shaped closed end after blow molding and has good inner surface dimensional accuracy. [Structure] A blow molding material is preliminarily formed into a tube shape, and a core die 30 is provided inside an opening end of the preforming tube 28.
Is inserted into the blow molding die 34 together with the core die 30, and the preformed tube 28 is softened by heating thereafter or prior to this. And blow molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a hose, and more particularly to a hose that is required to have gasoline resistance and gasoline permeation resistance such as a filler hose for automobiles and an air intake hose that is required to have oil resistance and heat resistance. The present invention relates to a manufacturing method suitable for manufacturing.

[0002]

2. Description of the Related Art Filler hoses (fuel hoses) for automobiles and the like are conventionally made of rubber materials such as NBR / PVC rubber, which are resistant to gasoline and gasoline permeation. There is.

However, regulations on gasoline permeation have become stricter in recent years, and it has become difficult to cope with the above-mentioned conventional hose composed of a single rubber layer.

In such a situation, as shown in FIG. 7A, a thin fluororubber film (inner layer) 102 is formed inside the rubber outer layer 100, or the hose is made of resin. Things are being considered.

In the case of the former hose in which the fluororubber membrane 102 is lined, the performance is good, but there is a problem that the cost is high, and it is difficult to adopt it in reality.

On the other hand, in the case of the latter resin hose, a hard resin material is generally superior in gasoline resistance and gasoline permeation resistance in the present materials, so that it is made of a hard resin. In this case, the hose becomes poor in flexibility, and there arises a problem that sufficient sealing performance cannot be obtained when the mating pipe is inserted into the end of the hose.

Therefore, in the case of such a resin hose, it may be considered that only the end portion connected to the mating pipe is made of a soft resin material (for example, bending elastic modulus of 500 kg / cm ² or less).

By the way, a blow molding method is preferably adopted as a molding method of this resin hose. However, in the case of blow molding, since the parison is inflated by blowing air to form a predetermined shape, the dimensional accuracy of the inner surface is poor. Become.

If the dimensional accuracy of the inner surface of the end of the hose is poor, sufficient sealing performance cannot be obtained when the mating pipe is inserted into the same end. Therefore, after that, finishing work such as polishing of the inner surface of the end portion is required for dimensioning.

However, when such a polishing process is performed, polishing powder remains on the same portion, and a step for cleaning the polishing powder is required later, which complicates the hose manufacturing process.

For this reason, various molding methods which do not require polishing or the like have been studied later, but in the case of these molding methods, there is a problem that the mold and equipment are complicated. When the hose end is made of soft resin material like this,
There is also a problem that the gasoline permeation resistance and the like at the ends also deteriorate.

On the other hand, as shown in FIG. 7B, the resin hose has a two-layer laminated structure and the outer layer 104
If a soft resin material is used as the inner layer 106 and a hard resin material having excellent gasoline resistance, gasoline permeation resistance, etc. is used as the inner layer 106, the flexibility of the hose including the ends and the gasoline permeation resistance will be improved. It is possible to improve the properties such as the property.

As a method of manufacturing this hose having a laminated structure,
Although a method of blow molding a resin parison having a laminated structure of a thick and soft resin and a thin and hard resin can be adopted, in this case, the flexibility of the end of the hose can be secured, but the inner diameter dimensional accuracy becomes poor. In this case, if the inner surface of the end portion is subjected to polishing or the like, there arises a problem that the thin-film resin inner layer 106 that has been carefully formed is scraped off.

In general, in blow molding, since the parison is inflated by blowing air, it is necessary to close the end portion in a bag shape, and therefore the bag-shaped closed end portion is cut off later. Therefore, there is a problem that the hose is complicated and the material is lost accordingly.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its gist is to preform a blow molding material into a tubular shape in advance and to open the preformed tube at its open end. The core die is inserted into the inner side of the part to close the end portion and the inner diameter is regulated, and in this state, the preforming tube is set inside the outer surface molding member together with the core die, and after or in advance thereof, The preforming step is to heat the preforming tube by heating in a separate heating step and then blow mold the preforming tube.

[0016]

As described above, according to the present invention, a core mold is inserted inside the open end of a tube preformed to a predetermined length and blow molding is performed with the core closed. Therefore, it is not necessary to close the end portion of the preformed tube into a bag shape during blow molding.

Therefore, unlike the conventional method, it is not necessary to cut off the end portion closed like a bag later, the material loss is reduced accordingly, and the processing steps are simplified to reduce the processing cost. .

In general, in blow molding, a large-scale and complicated equipment including a portion for molding a parison in a molten state (injection machine, extruder, etc.) and a portion for performing mold clamping and blowing is used. , Further requires a step of adjusting the dimension of the inner surface of the end portion, but according to the present invention, by using a normal simple blow molding die, polishing of the inner surface of the end portion is not required, and the accuracy of the end portion dimension is good. The hose can be obtained, and the cost of the mold and equipment can be reduced.

In the present invention, a tube to be blow-molded is pre-molded and then a core die is attached to the open end of the pre-molded tube for blow molding. Therefore, a large amount is prepared in advance. It has the feature that various kinds of hoses can be manufactured by simply changing the type of blow mold using the preformed tube that has been set aside. That is, according to the present invention, when manufacturing various types of hoses, the steps up to obtaining the preformed tube can be made common.

Further, when the preformed tube is blow-molded, it is heated and softened in a heating step separate from that of the pre-molding, so that the pre-molded tube can be satisfactorily blow-molded even if it is once cooled. Therefore, even a thin preformed tube can be blow-molded satisfactorily (the parison in the molten state (softened state) is injection-molded, and while maintaining the softened state, this is set in the blow-molding die to perform the blow operation. If this is done, it must be thicker than a certain thickness to prevent the parison from cooling rapidly).

In the present invention, the preformed tube has a laminated structure of a thick resin outer layer and a thin resin inner layer, and the preformed tube having the laminated structure can be subjected to blow molding operation.

According to this method, the filler hose, the air duct hose, and the like, which are composed of the thick soft resin outer layer and the thin hard resin inner layer, are kept at the end while having a two-layer structure made of the same material. Blow molding can be performed while maintaining good dimensional accuracy of the inner surface.

[0023]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 shows an example of a hose such as a filler hose or an air intake hose. The hose 10 shown in FIG. 2 (A) has a thick resin outer layer 12 (for example, a wall thickness of 2 mm or more).
And a thin (for example, a wall thickness of 0.5 mm or less) resin inner layer 14
And a bellows portion 16 is formed at a middle portion in the longitudinal direction.

Here, the thick resin outer layer 12 is made of a soft material (for example, the bending elastic modulus is 500 kg / cm ² or less), and the thin resin inner layer 14 is resistant to internal fluids (gasoline resistance, gasoline permeation resistance). It is made of a hard resin material with excellent properties.

The hose 18 of (B) is also composed of a soft and thick resin outer layer 12 and a thin and inner fluid resistant thin resin inner layer 14, and has a bent portion 20 approximately in the middle in the longitudinal direction.
It has a curved shape. Then, a bellows portion 16 is formed on one side of the bent portion 20 in the same manner as the hose 10.

The hose 22 of (C) is the hose 10,
Similar to 18, a thick and soft resin outer layer 12 and a thin and hard inner resin layer 14 having a good internal fluid resistance form a laminated structure. However, this hose 22 does not have a bellows-shaped portion, but has two bent portions 24 and 26 that are curved.

FIGS. 1 and 3 show an example of a method for manufacturing the hose 10. As shown in the figure, in the manufacturing method of this example, a resin material is preformed to form a thick resin outer layer 12
A preformed tube 28 having a two-layer laminated structure of the resin inner layer 14 and the thin resin inner layer 14 is manufactured. Here, the pre-molding of the tube 28 may be carried out by injection molding such as injection molding.
Tube 28 having a uniform cross section in the longitudinal direction as shown in the figure
In the case of, an extrusion molding method is suitable.

The preformed tube 28 can be obtained by, for example, continuously extruding a long tube and cutting it into a suitable length. That is, a large amount of preformed tubes 28 can be prepared in advance at the preforming stage.

Now, when the preformed tube 28 is prepared,
Next, as shown in (B), the core mold 3 is placed inside both ends thereof.
0 is inserted in a close contact state, the end opening is closed by these core molds 30 and the inner surface of the end is constrained, and then the preforming tube 28 is heated until it is in a substantially molten state. As the heating means, various methods such as heating by an oven, far infrared heating, radiant heating, hot air heating, dielectric heating can be adopted.

After the preforming tube 28 is heated to a substantially molten state, it is then blown together with the core die 30 into a blow molding die 34.
Blow hole 32 formed in one core mold 30 as shown in (D).
Further, air is blown to inflate the preforming tube 28 until it comes into close contact with the inner surface of the cavity 36, and this is molded into a predetermined shape. Thereafter, the hose product can be obtained by removing the mold from the blow mold 34. The heat softening of the preforming tube 28 can be performed in a state where it is set in the blow molding die 34.

Thus, in this method, the preformed tube 2
Since the blow molding is performed with both ends of 8 being closed by the core die 30, it is not necessary to keep the ends of the preforming tube 28 itself in a bag shape. Therefore, the step of cutting the bag-like closed portion thereafter is not required, and therefore, the material loss due to the cutting does not occur, and the product can be obtained as it is by blow molding, so that the processing step is also simplified.

Further, since blow molding is performed with the core die 30 in a state where the inner surface of the end portion of the preformed tube 28 is regulated, a blow molded product (hose 10) having a good dimensional accuracy of the inner surface of the end portion can be obtained.

FIG. 3 shows an example of another manufacturing method.
In this example, after inserting the core die 30 into the end portion of the preforming tube 28, first the end die 38a of the blow molding die is set as shown in (A), and then preforming as shown in (B). An example is shown in which the tube 28 is heated and softened and then the split type main body mold 38b is set and blow molded.

In FIG. 4, the core mold 30 is inserted into the end portion of the preforming tube 28, and the preforming tube 28 is heated and loaded into a blow molding die 40 having a curved cavity 42. This is an example of the case of blowing and molding into a predetermined shape. The hose 18 can be obtained by this method.

As another method of manufacturing the hose 18, as shown in FIG. 5, the end mold 44a is first set, and then the split type main mold 44b is set, and then the blow molding operation is performed. It is also possible to adopt.

FIG. 6 shows an example of the shape of the preformed tube. The preformed tube 48 of (A) has a single layer structure of resin and has a uniform thickness in the longitudinal direction.

The preformed tube 50 of (B) has a single-layer structure of resin similarly, and has a thick wall portion 52 at a portion excluding the end portion in the longitudinal direction, that is, a portion whose wall thickness becomes thin during blow molding. In this way, the blow-molded product having a uniform thickness can be obtained by previously forming the thick portion in the blow-molding so that the thickness becomes thin.

The preformed tube 54 of (C) has a two-layer laminated structure of the resin outer layer 12 and the resin inner layer 14, and has the thick portion 56 formed by projecting the intermediate portion in the longitudinal direction inward. is there.

The preformed tube 58 of (D) is obtained by alternately changing the wall thicknesses of the resin outer layer 12 and the resin inner layer 14 in the longitudinal direction, and the preformed tube 60 of (E) is
The resin inner layer 14 has a thick intermediate portion in the longitudinal direction. Further, in the preformed tube 62 of (F), the outer resin layer 12 and the inner resin layer 14 are made to have a generally smaller diameter in the longitudinal middle portion.

It is to be noted that extrusion molding is suitable for the preformed tubes 48 and 58 of (A) and (D) in FIG. 6, and the preformed tubes of (B), (C), (E) and (F). 5
Injection molding is suitable for 0, 54, 60 and 62.

Although the embodiment of the present invention has been described in detail above, this is merely an example. The present invention can be applied to a hose having a combination of an outer layer and an inner layer made of another material, or a single-layer structure. Further, when manufacturing a hose having a laminated structure, the outer layer is formed in a final shape in advance. It is also possible to preform only the inner layer, set it inside the outer layer, and perform a blow molding operation to obtain a hose having a final shape. Others The present invention can be implemented in variously modified modes based on the knowledge of those skilled in the art without departing from the spirit of the invention.

[Brief description of drawings]

FIG. 1 is a process explanatory diagram of a hose manufacturing method that is an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a hose obtained by the method of the present invention.

FIG. 3 is an explanatory view of a method of another embodiment of the present invention.

FIG. 4 is an explanatory view of a method of still another embodiment of the present invention.

FIG. 5 is an explanatory view of a method of still another embodiment of the present invention.

FIG. 6 is a diagram showing an example of the shape of a preformed tube.

FIG. 7 is a background illustration of the present invention.

[Explanation of symbols]

10, 18, 22 Hose 12 Resin outer layer 14 Resin inner layer 28, 48, 50, 54, 58, 60, 62 Preforming tube 30 Core type 34, 40 Blow molding type 38a, 44a End part type 38b, 44b Main body type

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 31, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a hose, and more particularly to a hose that is required to have gasoline resistance and gasoline permeation resistance such as a filler hose for automobiles and an air intake hose that is required to have oil resistance and heat resistance. The present invention relates to a manufacturing method suitable for manufacturing.

[0002]

2. Description of the Related Art Filler hoses (fuel hoses) for automobiles and the like are conventionally made of rubber materials such as NBR / PVC rubber, which are resistant to gasoline and gasoline permeation. There is.

However, regulations on gasoline permeation have become stricter in recent years, and it has become difficult to cope with the above-mentioned conventional hose composed of a single rubber layer.

In such a situation, as shown in FIG. 7A, a thin fluororubber film (inner layer) 102 is formed inside the rubber outer layer 100, or the hose is made of resin. Things are being considered.

In the case of the former hose in which the fluororubber membrane 102 is lined, the performance is good, but there is a problem that the cost is high, and it is difficult to adopt it in reality.

On the other hand, in the case of the latter resin hose, a hard resin material is generally superior in gasoline resistance and gasoline permeation resistance in the present materials, so that it is made of a hard resin. In this case, the hose becomes poor in flexibility, and there arises a problem that sufficient sealing performance cannot be obtained when the mating pipe is inserted into the end of the hose.

Therefore, in the case of such a resin hose, it may be considered that only the end portion connected to the mating pipe is made of a soft resin material (for example, bending elastic modulus of 500 kg / cm ² or less).

By the way, a blow molding method is preferably adopted as a molding method of this resin hose. However, in the case of blow molding, since the parison is inflated by blowing air to form a predetermined shape, the dimensional accuracy of the inner surface is poor. Become.

If the dimensional accuracy of the inner surface of the end of the hose is poor, sufficient sealing performance cannot be obtained when the mating pipe is inserted into the same end. Therefore, after that, finishing work such as polishing of the inner surface of the end portion is required for dimensioning.

However, when such a polishing process is performed, polishing powder remains on the same portion, and a step for cleaning the polishing powder is required later, which complicates the hose manufacturing process.

For this reason, various molding methods which do not require polishing or the like have been studied later, but in the case of these molding methods, there is a problem that the mold and equipment are complicated. When the hose end is made of soft resin material like this,
There is also a problem that the gasoline permeation resistance and the like at the ends also deteriorate.

On the other hand, as shown in FIG. 7B, the resin hose has a two-layer laminated structure and the outer layer 104
If a soft resin material is used as the inner layer 106 and a hard resin material having excellent gasoline resistance, gasoline permeation resistance, etc. is used as the inner layer 106, the flexibility of the hose including the ends and the gasoline permeation resistance will be improved. It is possible to improve the properties such as the property.

As a method of manufacturing this hose having a laminated structure,
Although a method of blow molding a resin parison having a laminated structure of a thick and soft resin and a thin and hard resin can be adopted, in this case, the flexibility of the end of the hose can be secured, but the inner diameter dimensional accuracy becomes poor. In this case, if the inner surface of the end portion is subjected to polishing or the like, there arises a problem that the thin-film resin inner layer 106 that has been carefully formed is scraped off.

In general, in blow molding, since the parison is inflated by blowing air, it is necessary to close the end portion in a bag shape, and therefore the bag-shaped closed end portion is cut off later. Therefore, there is a problem that the hose is complicated and the material is lost accordingly.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its gist is to preform a blow molding material into a tubular shape in advance and to open the preformed tube at its open end. The core die is inserted into the inner side of the part to close the end portion and the inner diameter is regulated, and in this state, the preforming tube is set inside the outer surface molding member together with the core die, and after or in advance thereof, The preforming step is to heat the preforming tube by heating in a separate heating step and then blow mold the preforming tube.

[0016]

As described above, according to the present invention, a core mold is inserted inside the open end of a tube preformed to a predetermined length and blow molding is performed with the core closed. Therefore, it is not necessary to close the end portion of the preformed tube into a bag shape during blow molding.

Therefore, unlike the conventional method, it is not necessary to cut off the end portion closed like a bag later, the material loss is reduced accordingly, and the processing steps are simplified to reduce the processing cost. .

In general, in blow molding, a large-scale and complicated equipment including a portion for molding a parison in a molten state (injection machine, extruder, etc.) and a portion for performing mold clamping and blowing is used. , Further requires a step of adjusting the dimension of the inner surface of the end portion, but according to the present invention, by using a normal simple blow molding die, polishing of the inner surface of the end portion is not required, and the accuracy of the end portion dimension is good. The hose can be obtained, and the cost of the mold and equipment can be reduced.

In the present invention, a tube to be blow-molded is pre-molded and then a core die is attached to the open end of the pre-molded tube for blow molding. Therefore, a large amount is prepared in advance. It has the feature that various kinds of hoses can be manufactured by simply changing the type of blow mold using the preformed tube that has been set aside. That is, according to the present invention, when manufacturing various types of hoses, the steps up to obtaining the preformed tube can be made common.

Further, when the preformed tube is blow-molded, it is heated and softened in a heating step separate from that of the pre-molding, so that the pre-molded tube can be satisfactorily blow-molded even if it is once cooled. Therefore, even a thin preformed tube can be blow-molded satisfactorily (the parison in the molten state (softened state) is injection-molded, and while maintaining the softened state, this is set in the blow-molding die to perform the blow operation. If this is done, it must be thicker than a certain thickness to prevent the parison from cooling rapidly).

In the present invention, a blow molding material is preliminarily formed into a tube.
Blow molding by inserting a core mold into the end after preforming into a shape
The preforming step and its
Separate production line for core die insertion, blow molding process, etc.
On the same line or on one continuous production line
Both cases are included.

In the present invention, the preformed tube has a laminated structure of a thick resin outer layer and a thin resin inner layer, and the preformed tube having the laminated structure can be subjected to blow molding operation.

According to this method, the filler hose, the air duct hose, and the like, which are composed of the thick soft resin outer layer and the thin hard resin inner layer, have their end portions kept in a two-layer structure made of the same material, and also have the end portions. Blow molding can be performed while maintaining good dimensional accuracy of the inner surface.

[0024]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 shows an example of a hose such as a filler hose or an air intake hose. The hose 10 shown in FIG. 2 (A) has a thick resin outer layer 12 (for example, a wall thickness of 2 mm or more).
And a thin (for example, a wall thickness of 0.5 mm or less) resin inner layer 14
And a bellows portion 16 is formed at a middle portion in the longitudinal direction.

Here, the thick resin outer layer 12 is made of a soft material (for example, the bending elastic modulus is 500 kg / cm ² or less), and the thin resin inner layer 14 is resistant to the internal fluid (gasoline resistance, gasoline permeation resistance). It is made of a hard resin material with excellent properties.

The hose 18 of (B) is also composed of a soft and thick resin outer layer 12 and a thin and inner fluid resistant thin resin inner layer 14, and has a bent portion 20 approximately in the longitudinal direction.
It has a curved shape. Then, a bellows portion 16 is formed on one side of the bent portion 20 in the same manner as the hose 10.

The hose 22 of (C) is the hose 10,
Similar to 18, a thick and soft resin outer layer 12 and a thin and hard inner resin layer 14 having a good internal fluid resistance form a laminated structure. However, this hose 22 does not have a bellows-shaped portion, but has two bent portions 24 and 26 that are curved.

FIGS. 1 and 3 show an example of a method for manufacturing the hose 10. As shown in the figure, in the manufacturing method of this example, a resin material is preformed to form a thick resin outer layer 12
A preformed tube 28 having a two-layer laminated structure of the resin inner layer 14 and the thin resin inner layer 14 is manufactured. Here, the pre-molding of the tube 28 may be carried out by injection molding such as injection molding.
Tube 28 having a uniform cross section in the longitudinal direction as shown in the figure
In the case of, an extrusion molding method is suitable.

The preformed tube 28 can be obtained, for example, by continuously extruding this into a long shape and cutting it into a suitable length. That is, a large amount of preformed tubes 28 can be prepared in advance at the preforming stage.

Now, when the preformed tube 28 is prepared,
Next, as shown in (B), the core mold 3 is placed inside both ends thereof.
0 is inserted in a close contact state, the end opening is closed by these core molds 30 and the inner surface of the end is constrained, and then the preforming tube 28 is heated until it is in a substantially molten state. As the heating means, various methods such as heating by an oven, far infrared heating, radiant heating, hot air heating, dielectric heating can be adopted.

After the preforming tube 28 is heated to a substantially molten state, it is then blown together with the core die 30 into a blow molding die 34.
Blow hole 32 formed in one core mold 30 as shown in (D).
Further, air is blown to inflate the preforming tube 28 until it comes into close contact with the inner surface of the cavity 36, and this is molded into a predetermined shape. Thereafter, the hose product can be obtained by removing the mold from the blow mold 34. The heat softening of the preforming tube 28 can be performed in a state where it is set in the blow molding die 34.

Thus, in this method, the preformed tube 2
Since the blow molding is performed with both ends of 8 being closed by the core die 30, it is not necessary to keep the ends of the preforming tube 28 itself in a bag shape. Therefore, the step of cutting the bag-like closed portion thereafter is not required, and therefore, the material loss due to the cutting does not occur, and the product can be obtained as it is by blow molding, so that the processing step is also simplified.

Further, since blow molding is performed with the core die 30 in a state where the inner surface of the end portion of the preformed tube 28 is regulated, a blow molded product (hose 10) having a good dimensional accuracy of the inner surface of the end portion can be obtained.

FIG. 3 shows an example of another manufacturing method.
In this example, after inserting the core die 30 into the end portion of the preforming tube 28, first the end die 38a of the blow molding die is set as shown in (A), and then preforming as shown in (B). An example is shown in which the tube 28 is heated and softened and then the split type main body mold 38b is set and blow molded.

In FIG. 4, the core mold 30 is inserted into the end portion of the preforming tube 28, and the preforming tube 28 is heated and loaded into a blow molding die 40 having a curved cavity 42. This is an example of the case of blowing and molding into a predetermined shape. The hose 18 can be obtained by this method.

As another method of manufacturing the hose 18, as shown in FIG. 5, the end mold 44a is first set, and then the split type main mold 44b is set, and then the blow molding operation is performed. It is also possible to adopt.

FIG. 6 shows an example of the shape of the preformed tube. The preformed tube 48 of (A) has a single layer structure of resin and has a uniform thickness in the longitudinal direction.

The preformed tube 50 of (B) has a single layer structure of resin similarly, and has a thick wall portion 52 at a portion excluding the end portion in the longitudinal direction, that is, a portion having a thin wall thickness during blow molding. In this way, the blow-molded product having a uniform thickness can be obtained by previously forming the thick portion in the blow-molding so that the thickness becomes thin.

The preformed tube 54 of (C) has a two-layer laminated structure of the resin outer layer 12 and the resin inner layer 14, and has the thick portion 56 formed by projecting the middle portion in the longitudinal direction inward. is there.

The preformed tube 58 of (D) is obtained by alternately changing the wall thicknesses of the resin outer layer 12 and the resin inner layer 14 in the longitudinal direction, and the preformed tube 60 of (E) is
The resin inner layer 14 has a thick intermediate portion in the longitudinal direction. Further, in the preformed tube 62 of (F), the outer resin layer 12 and the inner resin layer 14 are made to have a generally smaller diameter in the longitudinal middle portion.

Extrusion molding is suitable for the preformed tubes 48 and 58 of (A) and (D) in FIG. 6, and the preformed tubes of (B), (C), (E) and (F). 5
Injection molding is suitable for 0, 54, 60 and 62.

Although the embodiment of the present invention has been described in detail above, this is merely an example. The present invention can be applied to a hose having a combination of an outer layer and an inner layer made of another material, or a single-layer structure. Further, when manufacturing a hose having a laminated structure, the outer layer is formed in a final shape in advance. It is also possible to preform only the inner layer, set it inside the outer layer, and perform a blow molding operation to obtain a hose having a final shape. Others The present invention can be implemented in variously modified modes based on the knowledge of those skilled in the art without departing from the spirit of the invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29L 23:22 4F

Claims (2)

[Claims] 1. A blow molding material is preliminarily formed into a tube shape, and a core die is inserted inside the opening end of the preforming tube to close the end and regulate the inner diameter, and the preforming is performed in that state. The tube is set inside the outer surface forming member together with the core mold, and after or prior to this, the preforming tube is softened by heating in a heating step separate from the preforming step, and then the preforming is performed. A method for producing a hose, which comprises blow-molding a tube. 2. The method for producing a hose according to claim 1, wherein the preformed tube has a laminated structure of a thick resin outer layer and a thin resin inner layer.