JPS60223640A - Production of pipe bend - Google Patents

Abstract

PURPOSE:To produce a pipe bend having an intricate shape with good accuracy and high efficiency by disposing a core formed by embedding a reinforcing core material consisting of a flexible continuous body into a consumable material into a casting mold, pouring a forming material into the mold and curing the same. CONSTITUTION:The core 12 consisting of inactive aggregate such as sand and the consumable material such as fused salt, low melting alloy or synthetic resin which is softened or dissolved by water, heat, chemical, etc. and can be thus removed is disposed into the casting mold 13 consisting of a cope 13a and a drag 13b. The prescribed forming material is poured into the cavity 14 of said mold. The reinforcing core material 15 which connects plural core members 16 by spherical joints to constitute a flexible shaft and forms end faces 16a, 16b developing in the direction intersecting with the axial direction of the core 12 between the respective core member 16 is embedded into said core 12. The mold 13 is opened upon curing of said forming material, then the formed product is taken out and the consumable material of the core 12 is consumed by means such as heating or dissolving and thereafter the material 15 is drawn out and the pipe bend having the curved part is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD This invention relates to a method of manufacturing a tube body having a curved portion.

BACKGROUND OF THE INVENTION Pipe bodies with curved parts, such as L-shaped pipe joints, have been used in various fields, and they have been manufactured by various methods as described below.

First, as shown in FIG. 1, extrusion molding or other methods of mechanically bending a pipe to form a curved pipe have been carried out. However, this method has disadvantages in that it is not easy to process the resulting curved pipe into the desired shape, and the accuracy is poor.

Additionally, there was a problem in that it was difficult to provide localized protrusions, such as ribs, which were provided on the pipe wall as needed, such as ribs that protruded from the pipe inner wall surface in a direction intersecting the pipe axis direction, by integral molding. .

Further, in Japanese Patent Publication No. 58-37136, as shown in Fig. 2, a reinforcing fiber layer 2 containing a thermosetting resin is molded,
At the high temperature at which the thermosetting resin hardens, it has a vapor pressure greater than atmospheric pressure, and the elastic tube 4 is filled with a substance 3 that is liquid at room temperature.
112, and by applying heat while storing them in the mold 5, the tube 4 is expanded by the vapor pressure of the substance 3, thereby pressing the reinforcing fiber layer 2 against the inner wall of the mold 5. A method of manufacturing hollow tubes is described by curing. According to this method, it is possible to manufacture the shape of the curved part, small focus, mountain power, ridge, slope, etc. with high precision.
The method described in Publication No. 36 has the problem that not only the materials to be molded are considerably limited, but also that it is difficult to obtain a hollow tube having a uniform wall thickness.

Furthermore, as shown in the third factor, Japanese Patent Publication No. 43-23781 describes a method for manufacturing a bent pipe using a molding device in which cores 6a and 6b that can move forward and backward are inserted into a mold 7. There is.

However, in the case of this method, if the shape of the target product becomes complicated, it becomes difficult to take out the core, so the shapes of the hollow tubes that can be manufactured are extremely limited. For example, as shown in Fig. 4 or 5 There is a drawback that if the hollow tube body 8a or 8b, which is the object of manufacture, has at least two curved (bent) parts, it cannot be molded.

Therefore, conventionally, as shown in FIG. 6, reinforcing core material 9a,
A method of manufacturing a hollow tube body is carried out using a molding apparatus in which a core 10 made of a fugitive material and equipped with a core 9b is disposed in a mold 11.

According to this method, after molding, the fugitive material of the core 10 is mixed with water,
By softening and dissolving it with heat, chemicals, etc., it disappears and the desired hollow tube body can be obtained.

Therefore, even when manufacturing the hollow tube body 8a or 8b as shown in FIG. 4 or FIG. 5, the fugitive material of the core can be easily removed from the product.

However, even with the method using the core 10 made of a fugitive material, there is a disadvantage that depending on the shape of the intended hollow tube, it may be difficult to take out the reinforcing core material of the core from the molded product. Therefore, in such a case, as shown in the example in FIG.
It was designed to be equipped with a 19b. However, when the reinforcing core material is divided into pieces and not integrated, there is a drawback that the strength of reinforcing the core by the reinforcing core material is significantly reduced. Therefore, the method of manufacturing a hollow tube using a core made of a fugitive material in which a divided reinforcing core material is embedded, as described above, can only be applied when a low molding pressure is sufficient, such as when making a metal hoko. There wasn't.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional circumstances, and is capable of manufacturing even hollow tube bodies with complicated shapes with high precision and high efficiency, and can be applied to molding of various materials. The object of the present invention is to provide a method for manufacturing a bent pipe.

The structure of the invention, that is, the method for manufacturing a bent pipe of the present invention is to form a core by embedding a reinforcing core material made of a flexible continuous body in a fugitive material, and placing the core in a mold. The method is characterized in that a molding material is injected into the tube, and after the molding material has hardened, the fugitive material is made to disappear and the reinforcing core material is pulled out to obtain a tubular molded body.

This invention will be explained in more detail below.

FIG. 7 is a diagram showing a case where a bent pipe having two curved portions is manufactured by implementing the present invention. In this invention, a core 12 is formed from a fugitive material, and the core 12 is placed in a mold 13, whereby the molding material is injected.

The fugitive material forming the core 12 is a material that can be removed by softening or dissolving it with water, heat, chemicals, etc. For example, when the material used for molding is plastic, An aggregate made of molten salt using inert particles such as sand as shown in Japanese Publication No. 52-18226 can be used, and various low-melting point alloys can also be used. Furthermore, when the material to be molded is metal, various known materials made of synthetic resins using inert particles such as sand as aggregate can be used.

Further, in the present invention, a reinforcing core material 15 made of a flexible continuous body is embedded in the core 12 made of a fugitive material to provide reinforcement. As shown in FIG. 7, as the core material 15, for example, a plurality of core members 16 connected by a ball joint 17 to form a flexible shaft is used, and each core member 16 has a core 12 attached to it. In this invention, the core 12 obtained as described above is
As shown in FIG. 7, an upper mold 13a and a lower mold 13b are arranged.
are closed to sandwich the core 12 to form a cavity 14. The cavity 14 is filled with a molten molding material injected through a gate (not shown). Next, after the filled material has hardened, the upper mold 13a is opened and the molded product in which the core 12 has been cast is taken out from the lower mold 13b. Then,
When the fugitive material is made to disappear from the molded product taken out by an appropriate means, for example, by heating and melting, the core material 15 is removed.
A gap is created between the core material 15 and the molded product, and since the core material 15 is flexible, the core material 15 can be freely pulled out from inside the molded product to obtain the desired molded product.

In the above process, when injecting the molding material into the cavity 14 of the mold 13'' in which the core 12 is disposed, the core 12 is
In 2, the injection pressure of the molding material is applied.

Bending stress acts on the portion of the core 12 that faces the cavity 14. That is, as shown in FIG.
When attempting to bend the core 12, there is a neutral portion 12a that does not expand or contract in the curved portion of the core 12, and tensile stress acts on the outside of the neutral portion 12a as a boundary, while compressive stress acts on the inside. On the other hand, the various materials described above used as the fugitive materials forming the core 12 all exhibit stronger resistance to compressive stress than to tensile stress in an agglomerated state. Specifically, materials consisting of molten salt and sand or synthetic resin and sand exhibit about six times stronger resistance to compressive stress than to tensile stress, and low melting point metals such as lead-tin alloys exhibit resistance to tensile stress. It shows about three times higher resistance to compressive stress than

Therefore, if the core 12 is made of only fugitive material, the strength of the core 12 will reach its limit at the portion where the tensile stress is applied as shown in FIG. However, in this invention, the core 1
2 is equipped with a flexible core material 15, and in particular, in the embodiment shown in FIG.
6a and end surface 16b, even if bending stress acts on the curved portion of the core 12, the core 12 exhibits extremely high resistance to the bending stress for the following reason. That is, when bending stress is applied to the curved portion of the core 12, the adjacent core members 1
The end face 16a of one core member 16 of 6 and the other core member 16
The fugitive material between the end surfaces 16b and the end surface 16b is compressed between the end surfaces 16a and 16b, and a compressive stress acts on the fugitive material. However, as mentioned above, the fugitive material used for the core 12 exhibits extremely higher resistance to compressive stress than to tensile stress, and the fugitive material between end surfaces 16a and 16b resists compressive stress. Resist extremely strongly. the result,
Even if bending stress is applied to the curved portion of the core 12, the fugitive material of the gate between the end surfaces 16a and 161 strongly resists the force in the compressive direction, and the entire core 12 does not easily bend. Therefore, until the part of the core 12 on which tensile stress acts as shown in FIG. 8 breaks, the core 12 itself does not deform.
has extremely high strength.

In addition, as in the case of the above embodiment, the end surface 16 of the core member 16
The fugitive material of the core 12 is compressed when bending stress is applied to the core 12, even if the end face 16b and the end face 16b are not made into planar shapes that expand in the direction intersecting the axial direction of the core 12. If there are surfaces, the above-mentioned effects can be achieved, and for example, the end surfaces 16a and 16b can be made concave or the like. In that case, as long as the fugitive material has a surface that applies force in the compression direction, the core member 15 is not limited to the one in which the core members 16 are connected by a ball-and-socket joint as in the above-mentioned embodiment, but can be one using a universal joint. Or, depending on the case, a chain belt or the like may be used.

Effects of the Invention As described above, according to the method for manufacturing a bent pipe of the present invention, a core is formed from a fugitive material in which a core material made of a flexible continuous body is embedded, and the core is used to form a tubular shape. By manufacturing the molded body, even a tubular body having a complicated shape as shown in FIGS. 4 and 5, for example, can be easily manufactured with high precision.

In addition, since a flexible core with a continuous core material embedded in it is used, the strength of the core itself is improved, the material that can be molded is not limited, and the strength of the core is improved in this way. As a result, products with a large slenderness ratio (length/diameter value) can be easily manufactured.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a state in which a tube is formed by extrusion molding as an example of the prior art, FIG. 2 is a cross-sectional view showing another example of the prior art, and FIG. 3 is still another example of the prior art. Fig. 4 is a cross-sectional view showing an example of a curved pipe with a relatively complex external shape, Fig. 5 is a cross-sectional view showing another example, and Fig. 6 is a conventional pipe using fugitive material. FIG. 7 is a sectional view showing an embodiment of the method for manufacturing a curved pipe according to the present invention, and FIG. 8 explains the bending stress acting on the core. FIG. 12... Core, 13... Mold, 13'a...
Upper mold, 13b...lower mold, 14...cavity,
15... Reinforcement core material, 16... Core member, 16a.
... end face, 16b... end face. Applicant Toyota Motor Corporation Patent Attorney Agent Yutaka 1) Hisashi Take (and 1 other person) Figure 1 Figure 2 Figure 4 Figure 6 SoD Figure 8 Figure 7

Claims (1)

[Claims] A reinforcing core material made of a flexible continuous body is embedded in a fugitive material to form a core, the core is placed in a mold, a molding material is injected into the mold, and the molding material is cured. A method for manufacturing a curved pipe, characterized in that the fugitive material is then made to disappear and the reinforcing core material is pulled out to obtain a tubular molded body.