JPH09164586A - Manufacture of bend - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bend the preliminary molding of a thermoplastic resin straight pipe into a desired complex form easily, inexpensively, accurately, with good productivity. SOLUTION: Aluminum is extruded into a straight pipe 28 with a U-shaped cross section. A rod-shaped thermoplastic resin core material 30 which is flexible and has prescribed hardness is inserted into the U-shaped aluminum pipe. The pipe is bent by a bender, and then the core material 30 is removed to produce a bent molding 10 of a desired shape. An extruded straight thermoplastic resin pipe is inserted into the bent molding 10, set, and heat-treated, and the pipe is bent to obtain a bend of a desired shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a single tube or a multi-layer laminated tube made of a thermoplastic resin or rubber (elastomer) or a bent tube having a predetermined bent shape with a cross-sectional structure laminated by combining these.

[0002]

2. Description of the Related Art
For example, a bent tube made of a resin tube (thermoplastic resin tube) or a rubber tube is used for supplying fuel to an automobile, and this bent tube is used to form a fuel supply passage while avoiding interference with other members. , Has a three-dimensionally intricately winding shape.

Conventionally, this kind of bent pipe has been manufactured as follows. That is, a bending mold having a bending shape corresponding to the bending pipe is prepared, and a preform made of a resin material extruded in a straight tubular shape in advance is set in the fitting form, and then this is put in a heating furnace. After heat-molding at a predetermined temperature for a predetermined time, it was taken out of the furnace and cooled, and then demolded to obtain a bent tube.

FIG. 6 shows an example of a bending mold used in a method for manufacturing a bent pipe (Japanese Patent Laid-Open No. 59-57715).

In the method of this example, a half-split mold 200 formed by splitting a pipe having a predetermined curved shape with a circular cross section into a fastening piece 2
02, a pipe-shaped bending mold is fastened with a butterfly bolt 204, and a thickness is formed inside the bending mold that has a diameter smaller than the inner diameter of the bending mold and forms a gap with the inner surface of the bending mold. Straight tubular thermoplastic resin pipe (preform)
Is inserted from one end opening in the axial direction and set, and this is put in a heating furnace and bent.

In this method, a gap is formed between the preform and the outer peripheral surface thereof as described above.
The reason why a bending mold with a large inner diameter is used is
Since it takes time and effort to fasten or unfasten the half mold 200 when setting the resin pipe as the preform into the bending mold, opening the one end in the axial direction while keeping the half mold 200 in the tightened state. The preform is inserted through the mouth.

However, inserting the straight tubular preform into the pipe-shaped bending mold through the opening at the one end in the axial direction requires the resistance against resistance in the bent portion and the like, and therefore the setting work is performed. In addition, it is necessary to unfasten the half mold 200 and separate them when taking out the bent product, that is, the bent pipe from the bending mold after heating and cooling, which is troublesome. There is a problem that takes.

In addition, since there is a gap between the inner peripheral surface of the bending mold and the outer peripheral surface of the preform, there is a problem inevitably that the accuracy of the bent shape when bending is inferior. Further, there is a problem that it is very difficult to cut a pipe having a predetermined bent shape and a circular cross section, that is, it is difficult to obtain such a half mold 200.

On the other hand, using only the half mold 200,
That is, when the bending mold has a semicircular cross-section and the inner diameter is set to the inner diameter corresponding to the outer diameter of the preform and the preform is set and bent, the bending mold of the preform is Although it can be set and removed from the bending mold with good workability, the preform is partly separated from the bending mold, particularly in the bent shape part, or is not sufficiently adhered to the inner surface of the bending mold. As a result, there arises a problem that bending cannot be favorably performed.

On the other hand, as shown in FIG.
6, 208, 210 are welded to each other to manufacture a bending mold 212 having a rectangular cross section and a predetermined bending shape, and a straight tubular preform is set in the bending mold 212 through the opening on the upper surface in the figure. A method of bending by heating is also considered.

However, even in this case, there is a problem that a gap is formed between the preform having a circular cross section and the inner surface of the corner of the bending mold 212, and it is difficult to obtain a bending mold that is three-dimensionally bent. There is a problem that it is difficult to obtain a desired bent shape.

[0012]

The invention of the present application has been made to solve such a problem. Thus, the first invention of the present application is to bend a straight tubular preform made of substantially thermoplastic resin or unvulcanized or semi-vulcanized rubber having a constant outer diameter and a constant length into a predetermined curved shape. A method of manufacturing a bent pipe by processing, wherein the inner peripheral surface and the outer peripheral surface have a semicircular shape, and the inner diameter is set to an inner diameter of a size that fits into the outer peripheral surface of the bent pipe with substantially no clearance. An outer peripheral surface of the semi-circular portion has an arc shape continuous with the outer peripheral surface of the semi-circular portion, and an inner peripheral surface of the semi-circular portion extends straight in the outer peripheral surface direction continuously with the inner peripheral surface of the semi-circular portion. A bending mold having a U-shaped groove having an opening on the outer peripheral surface having a width substantially equal to the outer diameter of the preform, the bending mold having a predetermined curved shape in the axial direction. On the other hand, the extrusion-molded straight tubular preform is introduced from the opening of the bending mold into the U-shaped groove. It is characterized in that the semicircular shaped portion is pushed into a state of being closely fitted to the inner peripheral surface of the semicircular shaped portion and set, and then they are heat treated to be molded, and then a cooling step is performed to remove the mold (claim 1). .

According to the second aspect of the present invention, a bent pipe is manufactured by bending a straight tubular preform having a constant outer diameter and a constant length and made of a substantially thermoplastic resin into a predetermined bent shape. A method comprising: (a) a semicircular portion having an inner peripheral surface and an outer peripheral surface having a semicircular shape, and having an inner diameter of a size that fits into the outer peripheral surface of the curved pipe with substantially no gap;
The outer peripheral surface has an arc shape continuous with the outer peripheral surface of the semicircular portion, and the inner peripheral surface has a continuous extended portion that is continuous with the inner peripheral surface of the semicircular portion and extends straight in the outer peripheral surface direction. Formed and formed,
Forming a straight U-shaped tube having a U-shaped groove having an opening on the outer peripheral surface having a width substantially equal to the outer diameter of the preform by extrusion molding of a metal material and cutting thereof (b) The shape of the outer peripheral surface of the portion located in the opening has a cross-sectional shape that fits tightly into the inner peripheral surface of the U-shaped groove, and the shape of the outer peripheral surface of the extension portion is from the opening side end portion in the circumferential direction to the opening center portion side. A step of forming a rod-shaped flexible core material having a shape projecting outward in the radial direction by (c) loading the core material into the U-shaped groove in a fitted state, and A step of obtaining a U-tube-core material composite obtained by filling the core material with the core material; (d) bending the composite material into the predetermined curved shape; and (e) using the bent composite material. A step of taking out the core material and obtaining a bending mold having the U-shaped groove, which has the predetermined bending shape in the axial direction; A step of inserting a straight preform into the U-shaped groove of the bending mold and the inner peripheral surface of the semicircular portion through the opening so as to be in close contact with the bending mold; A step of bending and forming the preform by inserting and setting the preform, and (h) performing a cooling treatment after the heating step, and thereafter, bending the bend pipe inside the bend forming die. And a step of removing from the bending mold.

According to a third aspect of the present invention, a straight pipe-shaped preform made of unvulcanized or semi-vulcanized rubber having a constant outer diameter and a constant length is bent into a predetermined bent shape. (A) A semicircular shape in which the inner peripheral surface and the outer peripheral surface have a semicircular shape, and the inner diameter is an inner diameter of a size that fits into the outer peripheral surface of the curved pipe with substantially no gap. Extension of the shape in which the outer peripheral surface has an arc shape continuous with the outer peripheral surface of the semicircular portion, and the inner peripheral surface continuously extends in the outer peripheral surface direction continuously with the inner peripheral surface of the semicircular portion. A straight U-shaped tube having a U-shaped groove having an opening on the outer peripheral surface, the opening having a width substantially equal to the outer diameter of the preform is formed by extrusion molding of a metal material and cutting thereof. Forming step and (b) the opening having a cross-sectional shape that fits tightly on the inner peripheral surface of the U-shaped groove The outer peripheral surface shape of the portion of which are positioned,
A step of forming a rod-shaped flexible core material having a shape projecting outward in the radial direction from the end portion on the opening side in the circumferential direction of the extension portion to the side of the center portion of the opening; U
A step of loading the inside of the U-shaped groove in a fitted state to obtain a U-tube-core material composite obtained by filling the U-shaped groove with the core material; and (D) forming the composite into the predetermined curved shape. And (e) taking out the core material from the bent composite,
A step of obtaining a bending mold having the U-shaped groove that has the predetermined curved shape in the axial direction, and (f) the straight preform through the opening inside the U-shaped groove of the bending mold and A step of fitting and setting the inner peripheral surface of the semicircular portion in a close contact state; and (g) a preforming product by heat-vulcanizing them while the preforming product is fitted and set in the bending mold. And (h) after the heating and vulcanizing step, the bent tube inside the bending mold is taken out from the bending mold.

The bent pipe manufacturing method according to claim 4 of the present application is the method according to any one of claims 1, 2 and 3, wherein the end of the extension in the circumferential opening side is located inside at a predetermined position in the axial direction of the bending mold. The opening width is partially narrowed by bending so as to partially crush it.

The bent pipe manufacturing method according to claim 5 of the present application is the method according to any one of claims 1, 2, 3, and 4, wherein the axial end surface of the preform is provided at one end of the bending mold in the axial direction. While providing a stopper part that abuts against the
The other end of the bending mold in the axial direction is formed into an open shape, and the preform is fitted and set in the bending mold such that one end surface of the preform contacts the stopper.

According to a sixth aspect of the present invention, in the method for manufacturing a bent pipe according to the fifth aspect, a cross section in which the stopper portion is fitted / fixed to the inner peripheral surface of the semicircular portion of the bending mold with substantially no space therebetween. It is characterized by being made of a circular metal short pipe.

The bent pipe manufacturing method according to claim 7 of the present application is the method according to any one of claims 2, 3, 4, 5, and 6, wherein the outer peripheral surface shape of the portion of the core member located at the opening is the U-shaped portion. It is characterized in that it has a substantially circular shape together with the outer peripheral surface of the character tube.

[0019]

As described above, the invention of claim 1 uses a bending mold having a U-shaped cross section, which is formed by continuously forming an extension portion on a semicircular portion whose inner and outer peripheral surfaces are semicircular. According to the present invention, the straight tubular preform is set and bent into a desired shape by heating. The preform is easily set in the bending mold through the circumferential opening. In addition, the preform can be brought into close contact with the inner peripheral surface of the semicircular portion, and bending can be performed with high accuracy, and the bent pipe can be easily removed from the bending mold when demolding. be able to.

Further, in the present invention, the bending mold is formed with a continuous extension in a semicircular portion, and the extension serves as an embankment for preventing the preform from protruding, which is complicated. Even if the preform is set in a curved shape, the preform does not stick out of the bending mold, and the preform can be brought into a state in which it is in close contact with the inner surface of the mold even at the bend, and the bending process is accurate. You can do it high.

A second aspect of the present invention relates to a method for manufacturing a bent pipe substantially made of a thermoplastic resin.
A straight U-shaped tube is manufactured by extrusion-molding and cutting a metal material such as an aluminum material, and a flexible rod-shaped core material is loaded inside the U-shaped tube in a fitted state without a gap.
In that state, the U-shaped tube is bent into a desired shape to manufacture a bending mold, and a straight tubular preform which is substantially made of a thermoplastic resin is set on the bending mold, and then the desired shape is obtained by heating. According to the present invention, which is bent into a shape,
In the same manner as bending a metal pipe with a bender, a U-shaped pipe can be bent accurately and easily into a desired shape to manufacture a bending mold.

At this time, since a core material is loaded inside the U-shaped tube and the core material acts as a backup material, the U-shaped tube is not partially bent, crushed or buckled at the bent portion. This can be bent into a good curved shape.

In the present invention, the outer peripheral surface shape of the core material, specifically, the outer peripheral surface shape of the portion located at the opening of the U-shaped groove of the U-shaped tube is close to a circle or a circle together with the U-shaped tube outer peripheral surface. Since it is shaped like a shape, it is possible to bend the U-shaped tube with the core material loaded in the same manner as bending a circular pipe. This can be easily and accurately bent into a desired bent shape.

Further, after the bending, the inner peripheral surface of the bending mold has a U-shaped cross section, and the width of the opening in the circumferential direction is substantially equal to the outer diameter of the preform. Therefore, the core material can be easily taken out from the bending mold.

In the present invention, a thermoplastic resin having a predetermined hardness (eg, ultrahigh molecular weight polyethylene resin) is used as the core material.
It is preferable that the hardness thereof is Rockwell hardness (R scale) of 45 to 100 (20 ° C.) and the flexural modulus of elasticity is 1000 to 15000 kgf / cm ² .

If the hardness of the core material is less than 45, the core material may be partially crushed at the bent portion during bending and the U-shaped tube may be partially crushed. There is a risk that the character tube may be broken or that the core material cannot be taken out from the inside of the bending mold after bending. On the other hand, the bending elastic modulus of the core material is 1000 kgf / cm.
^If it is less than ² , the core material may be stretched during bending and the inner diameter of the bending mold and the opening width in the circumferential direction may be narrowed. If it exceeds 15,000 kgf / cm ² , the deformation resistance is too strong and the bending resistance may be too high. During processing, the U-shaped pipe may be broken or the bending itself may become difficult.

The invention of claim 3 relates to a method for manufacturing a bent pipe substantially made of rubber, wherein a bending mold manufactured in the same manner as the invention of claim 2 is substantially unvulcanized or semi-vulcanized. A straight tubular preform made of vulcanized rubber is set and then bent into a desired shape by heat vulcanization.According to the present invention, even if the bent pipe is made of a rubber material, it is heated. In the vulcanization process, it is possible to accurately perform bending into a desired shape.

According to a fourth aspect of the present invention, the end of the extension portion of the bending mold in the circumferential direction on the opening side is bent so as to be partially crushed inward at a predetermined axial position to partially narrow the opening width. Therefore, according to the present invention, the protrusion of the preform set in the bending mold can be more effectively prevented. Also, since the crushed part (bent part) of this extension is only partially formed at a predetermined location along the axial direction, after setting the preform on the bending mold or after heating / cooling. There is an advantage that workability in removing the bent pipe (after heat vulcanization) from the bending mold is not substantially impaired.

According to a fifth aspect of the present invention, a stopper portion is provided at one end portion in the axial direction of the bending mold, while the other end portion of the bending mold has an open shape. According to the present invention, a straight tubular preform is formed. When the product is set in the bending mold, the pre-formed product can be reliably and easily set at the specified position by bringing the axial end surface into contact with the stopper part. In addition to being able to easily perform the setting work to the molding die, it is possible to set the preform in a predetermined relational position relative to the bending mold,
There is an advantage that the bending accuracy is further increased.

According to a sixth aspect of the present invention, a metal short tube having a circular cross section is fitted into and fixed to the inner peripheral surface of the semi-circular portion of the bending mold without a gap to form the stopper portion. According to the present invention, By simply fixing the short pipe, it is possible to form the stopper part over the entire inner circumference of the semi-circular shaped part of the bending mold, and it is easy to fix the metal short pipe to the bending mold. The advantage that the entire axial end surface of the preform can be brought into contact with the stopper portion is obtained.

According to a seventh aspect of the present invention, the shape of the outer peripheral surface of the core material is formed so as to form a substantially circular shape together with the outer peripheral surface of the U-shaped tube. In the present invention, the U-shaped tube is formed. Since the entire outer peripheral surface shape of the core material and the core material is circular, bending can be performed more smoothly by using a bender without causing partial crushing.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, reference numeral 10 denotes a bending mold used to obtain a bent pipe 14 for supplying fuel for an automobile from a straight tubular preform 12 (see FIG. 2) which will be described in detail later, and is made of an aluminum material. , As a whole, bent pipe 14
It has a curved shape corresponding to the shape of.

As is clear from the cross-sectional shape shown in the drawing, the bending mold 10 has a U-shaped inner peripheral surface and an upward C-shaped outer peripheral surface, and extends in the circumferential direction over the entire axial length. It has a U-shaped groove that forms the opening 16 at a predetermined position. That is, the bending mold 10 includes a semicircular portion (lower half portion) 18 in which both the inner peripheral surface and the outer peripheral surface form a semicircular shape, and the inner peripheral surface of the semicircular portion 18 from both ends in the circumferential direction of the inner peripheral surface. It has an extension portion (upper half portion) 20 that has a straight surface shape that extends right above in the drawing and that has an outer peripheral surface that forms an arc shape that is continuous with the outer peripheral surface of the semicircular portion 18.

The semi-circular portion 18 is a portion to be fitted with the preform 12 when the bent pipe 14 is molded, and its inner diameter is substantially a clearance from the outer peripheral surface of the preform 12, that is, the bent pipe 14. It is sized to fit without.

As shown in the sectional view on the right side in FIG. 1, the extension portion 20 is formed with an inward pressing portion 22 at a predetermined axial position so as to prevent the preform 12 from protruding. The holding portion 22 is formed by bending the end portion of the extension portion 20 on the circumferential opening side so as to be partially crushed inward, whereby the width of the opening portion 16 of the bending mold 10 in the circumferential direction is partially formed. Has been narrowed to.

Further, one end of the bending mold 10 in the axial direction is
There is provided a stopper portion 24 that comes into contact with one end surface of the preform 12 to regulate the axial position of the preform 12.
The stopper portion 24 is a short tube made of an aluminum material and having a circular cross section, and is a semicircular portion 1 of the bending mold 10.
It is provided by being fitted and fixed to the inner peripheral surface of 8 with substantially no gap. On the other hand, the other end portion of the bending mold 10 in the axial direction is an open portion 26.

The preform 12 is a thermoplastic resin,
For example, a nylon resin is extruded into a straight tube and cut into a predetermined size. A method of manufacturing the bent pipe 14 from the preform 12 will be described with reference to FIG.

As shown in the figure, first, a straight tubular preform 12 is set in the bending mold 10 through an opening 16 in the circumferential direction (I, II). At this time, the position of the preform 12 in the axial direction is regulated by bringing one end surface in the axial direction into contact with the stopper portion 24, and the outer peripheral surface has the semicircular portion 1.
It is fitted on the inner peripheral surface of 8 without a gap. As a result, the preform 12 can be accurately bent in the subsequent heating step.

Subsequently, the bending mold 10 and the preform 12 are put into a heating furnace and heat-treated at a predetermined temperature for a predetermined time, then taken out of the furnace and cooled, and then the mold is removed. Here, the bent pipe 14 bent into a predetermined shape
Is obtained (III).

In the manufacturing method of this example, the bending mold 1 is used.
0, an extension 20 continuous with the semicircular portion 18 is formed, the bending mold 10 has a U-shaped cross section as a whole, and the extension 20 is set inside the bending mold 10. Since it acts as an embankment part for preventing the preformed product 12 from protruding, the preformed product 12 is prevented from protruding, especially in the bent portion, during the setting operation of the preformed product 12 in the bending mold 10 and the handling thereof. It

As a result, the preform 12 is bent into the bending mold 1
Bending can be performed with the inner peripheral surface of No. 0 being held in close contact with the inner peripheral surface, and the bending of the preform 12 can be performed with high shape accuracy.

Further, according to the method of manufacturing the bent pipe 14 in this example, the preform 12 can be further firmly held in the bending mold 10 by the pressing portion 22, and thus the preform can be held. The protrusion of 12 can be more reliably prevented, and the bending accuracy can be further improved. In addition, the inner peripheral surface of the extension portion 20 is a straight surface, and the opening width of the opening portion 16 in the circumferential direction is the semicircular shape portion 18.
Since it is the same as the inner diameter of the preformed product 12, it is possible to easily perform the setting operation when setting the preformed product 12 in the bending mold 10, and after the cooling, the bent molded product,
That is, the bent tube 14 can be smoothly released from the mold.

Next, a method of manufacturing the bending mold 10 will be described with reference to FIGS. In this example, first, a predetermined metal material, in this example, an aluminum material is extruded to manufacture a U-shaped tube 28 having a straight U-shaped cross section. Here, the U-shaped pipe 28 includes a semicircular portion 18 and an extension portion 20 that follows the semicircular portion 18.
And a form having.

In the manufacturing method of this example, as shown in FIG. 4, the U-shaped tube 28 prepared as described above is provided inside the U-shaped tube 28 over its entire length in the axial direction. A core material 30 having properties is loaded to form a composite (I), which is bent into a desired shape by a bender (I).
I) Then, the core material 30 is taken out and the bending mold 10 is manufactured (III).

Here, the core material 30 is obtained by extruding a flexible thermoplastic resin material, in this example, an ultrahigh molecular weight polyethylene resin material, and has a hardness of Rockwell hardness (R scale). ) Is 45 to 100 (20 ° C.) and the flexural modulus is 1000 to 15000 kgf / cm ² .

Here, the outer peripheral surface shape of the core material 30 will be described in detail. As is clear from FIG. 3, the cross-sectional shape is such that when the core material 30 is loaded into the U-shaped tube 28, the cross-sectional shape is combined. Are said to form a circle. That is, in the core material 30, in particular, the outer peripheral surface of the portion corresponding to the space between the both ends on the opening side of the extension portion 20 of the U-shaped tube 28 (opening 16) is continuous with the outer peripheral surface of the U-shaped tube 28. The outer peripheral surface of the U-shaped tube 28 has a circular cross section as a whole, and the surface shape of the portion corresponding to the inner peripheral surface of the U-shaped tube 28 is a shape that fits into the inner peripheral surface of the U-shaped tube 28 with substantially no clearance. ing.

In the method of manufacturing the bending mold 10 in this example, a straight U-shaped tube 28 made of an aluminum material is manufactured, and an ultrahigh molecular weight polyethylene resin material having flexibility inside the U-shaped tube 28. Since the rod-shaped core material 30 made of is substantially gaplessly loaded and thereafter they are bent, the U-shaped tube 28 is not partially bent, crushed or buckled at the bent portion. Even if the number of bent portions is large and the curved shape is three-dimensionally complicated,
This can be easily bent into a desired shape. At that time, it is also possible to easily bend the entire U-shaped pipe 28 on the side of the opening 16 in the circumferential direction.

In this example, the outer peripheral surface of the core material 30 is the core material 30.
Is shaped so as to have a circular cross-section when loaded into the U-shaped pipe 28, which allows the U-shaped pipe 28 to be bent in the same manner as a pipe having a circular cross-section, that is, Bending can be performed by a bender, so that the bending mold 10 having a desired shape can be easily and accurately obtained.

Further, in this example, the inner peripheral surface of the U-shaped tube 28 has a U-shaped cross section, and the opening width of the opening 16 in the circumferential direction is the same as the inner diameter of the semicircular portion 18, so that the bending is performed. The core material 30 can be easily taken out from the bending mold 10 after processing.

FIG. 5 shows another embodiment of the present invention, and particularly shows an example in which a core material 32 having a different shape is used in the method for manufacturing the bending mold 10 described above. The core material 32 in this example has an octagonal sectional shape as a whole, and when it is loaded inside the U-shaped tube 28, the core material 32 and the U-shaped tube 28 have a circular sectional shape as a whole. It is shaped so as to form an approximate shape. More specifically, in the core member 32, the shape of the outer peripheral surface of the portion of the extension portion 20 between the two ends on the opening side in the circumferential direction protrudes outward in the radial direction toward the center side of the opening 16 from the both ends. With the U-shaped tube 28, the outer peripheral surface as a whole has a cross-sectional shape that approximates a circle. Even if the U-shaped tube 28 is bent by a bender in this state, it can be easily processed into a good and desired bent shape.

The embodiments of the present invention have been described in detail above, but these are merely examples, and the present invention can be applied to the manufacture of bent pipes of uses and types other than those described above, for example. Further, the present invention can also be applied to the production of a thermoplastic resin single pipe, a thermoplastic resin laminated structure pipe, a rubber single pipe, or a bent pipe having a cross-sectional structure laminated by combining these, and the like. It can be implemented in a mode in which various changes are made without departing from the range.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of a bending mold used in a method for manufacturing a bent pipe according to the present invention.

FIG. 2 is a diagram showing a method for manufacturing a bent pipe which is an embodiment of the present invention using the bending mold shown in FIG.

FIG. 3 is an explanatory view showing essential steps of the method for manufacturing the bending mold of FIGS.

FIG. 4 is a diagram showing a method for manufacturing a bending mold in one embodiment of the present invention using the core material in FIG.

FIG. 5 is a view showing a cross-sectional shape of a core material used in manufacturing a bending mold according to another embodiment of the present invention together with a U-shaped tube. .

FIG. 6 is a view showing a bending mold used in a conventionally known method for manufacturing a bent pipe.

FIG. 7 is a view showing a bending mold used in a conventional manufacturing method different from that in FIG.

[Explanation of symbols]

 10 Bending Molds 12 Preforms 14 Bent Pipes 16 Openings 18 Semi-Circular Shapes 20 Extensions 24 Stoppers 28 U-Shaped Tubes 30, 32 Cores

Claims (7)

[Claims] 1. A bent pipe obtained by bending a straight tubular preform made of a substantially thermoplastic resin having a constant outer diameter and a fixed length or unvulcanized or semi-vulcanized rubber into a predetermined bent shape. In the method of manufacturing the inner peripheral surface and the outer peripheral surface is a semi-circular shape, and the inner diameter is a semi-circular shaped portion having an inner diameter of a size that fits into the outer peripheral surface of the curved pipe with substantially no gap,
The outer peripheral surface has an arc shape continuous with the outer peripheral surface of the semicircular portion, and the inner peripheral surface has a continuous extended portion that is continuous with the inner peripheral surface of the semicircular portion and extends straight in the outer peripheral surface direction. Formed and formed,
The straight tubular preform extruded from a bending mold having a U-shaped groove having an opening on the outer peripheral surface having a width substantially equal to the outer diameter of the preform and having a predetermined curved shape in the axial direction. The molded product is pushed into the U-shaped groove through the opening of the bending mold and set in a state of being closely fitted to the inner peripheral surface of the semi-circular shaped portion, and then they are heat-treated and molded, and thereafter, A method for manufacturing a bent pipe, which comprises demolding after a cooling step. 2. A method for producing a bent pipe by bending a straight tubular preform having a constant outer diameter and a constant length and made of a substantially thermoplastic resin into a predetermined bent shape. A semi-circular portion having an inner peripheral surface and an outer peripheral surface having a semi-circular shape and an inner diameter having an inner diameter of a size that fits into the outer peripheral surface of the curved pipe with substantially no gap, Of the semicircular portion, the inner peripheral surface of which is continuous with the outer peripheral surface of the semicircular portion, and the inner peripheral surface of the semicircular portion continuously extends straight in the direction of the outer peripheral surface. A step of forming a straight U-shaped tube having a U-shaped groove having an opening on the outer peripheral surface having a width substantially equal to the outer diameter of the product by extrusion molding of a metal material and cutting the same; and (B) the U-shaped groove Has a cross-sectional shape that fits tightly to the inner peripheral surface of the outer peripheral surface of the portion located at the opening. A step of forming a rod-shaped flexible core material having a shape protruding outward in the radial direction from the end portion on the opening side in the circumferential direction of the extension portion toward the center portion of the opening; A step of loading the inside of the U-shaped groove in a fitted state to obtain a U-tube-core material composite body in which the U-shaped groove is filled with the core material; A step of bending into a bent shape, and (e) a step of taking out the core material from the bent composite body, and obtaining a bending mold having the U-shaped groove, which has the predetermined bent shape in the axial direction ( F) a step of fitting the straight preform through the opening to the inside of the U-shaped groove of the bending mold and the inner peripheral surface of the semicircular portion in a close contact state, and (g) the bending mold A step of bending the preform by heating them with the preform fitted and set in Performs cooling processing in after h) heating process, the manufacturing method of the bent pipe, characterized in that it comprises a step of taking out from the bending mold a bent pipe of the mold inner bend in subsequent. 3. A method for manufacturing a bent pipe by bending a straight tubular preform made of unvulcanized or semi-vulcanized rubber having a constant outer diameter and a constant length into a predetermined bent shape. (A) A semicircular portion having an inner peripheral surface and an outer peripheral surface having a semicircular shape and having an inner diameter of a size that fits into the outer peripheral surface of the curved pipe with substantially no gap, An outer peripheral surface of the circular portion is formed in a continuous arc shape, and the inner peripheral surface is continuously formed on the inner peripheral surface of the semicircular portion to continuously form an extension portion of a form that extends straight in the outer peripheral surface direction, Forming a straight U-shaped tube having a U-shaped groove having an opening on the outer peripheral surface having a width substantially equal to the outer diameter of the preform by extrusion molding of a metal material and cutting thereof (b) Outer peripheral surface shape having a cross-sectional shape that fits tightly on the inner peripheral surface of the U-shaped groove and located at the opening A step of forming a rod-shaped flexible core material having a shape protruding outward in the radial direction from the end portion on the opening side in the circumferential direction of the extension portion to the side of the center portion of the opening; and (c) the core material. Is loaded into the U-shaped groove in a fitted state to obtain a U-tube-core material composite body in which the U-shaped groove is filled with the core material. And (e) taking out the core material from the bent composite body to obtain a bending mold having the U-shaped groove, which has the predetermined bending shape in the axial direction. (F)
A step of fitting the straight preform through the opening to the inside of the U-shaped groove of the bending mold and the inner peripheral surface of the semicircular portion in a close contact state; A step of bending and molding the preforms by heat-vulcanizing the preforms in a set state; and (h) bending the bent pipe inside the bending mold after the heat vulcanization step. A method of manufacturing a bent pipe, including the step of removing from a mold. 4. The method according to claim 1, wherein the end portion of the extension portion on the circumferential opening side is bent so as to be partially crushed inward at a predetermined axial position of the bending mold. A method for manufacturing a bent pipe, wherein the opening width is partially narrowed. 5. The stopper according to claim 1, 2, 3 or 4, wherein one end portion of the bending mold in the axial direction is in contact with an axial end surface of the preform to define an axial position. While providing a portion, the other axial end of the bending mold has an open shape, and the preform is fitted and set in the bending mold in such a state that one end surface of the preform contacts the stopper. And a method for manufacturing a bent pipe. 6. The stopper according to claim 5,
A method for manufacturing a bent pipe, which comprises a metal short pipe having a circular cross section that is fitted and fixed to the inner peripheral surface of the semicircular portion of the bending mold with substantially no gap. 7. The outer peripheral surface shape of a portion of the core member located at the opening has a substantially circular shape together with the outer peripheral surface of the U-shaped tube according to any one of claims 2, 3, 4, 5, and 6. A method for manufacturing a bent pipe, which is characterized in that the shape is formed.