JP3243574B2 - Blow forming method and apparatus for bent pipe joint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for blow molding a curved pipe joint, and more particularly, to a method for blow molding a resin curved pipe joint used for connecting a water pipe, a water supply pipe, a waste water pipe, and the like. Related to the device.

[0002]

2. Description of the Related Art Conventionally, in order to connect a pipe such as a water supply pipe made of vinyl chloride by changing its direction by 90 ° or 45 °, a bent portion having a predetermined radius of curvature and receiving portions at both ends are provided. Is used.

FIG. 4 is a diagram showing an example of a configuration of an injection molding apparatus used for manufacturing a conventional pipe joint. In FIG. 4, an injection molding apparatus 100 includes a cavity 101 for storing a molten resin, and a heating unit 109 arranged around the cavity.
A screw unit 102 disposed in the cavity, and a driving source 103 for applying a rotational force to the screw unit 102.
And a hopper 104 for supplying a resin material to the cavity 101.
A nozzle member 110 provided at one end of the cavity 101 for discharging resin, and a nozzle fixing member 10 for fixing the nozzle.
5, a mold fixing member 106 provided to face the nozzle 110, a nozzle fixing member 105 and a mold fixing member 106.
And a pair of rods 1 that guide the mold fixing member 106 in a direction to approach and separate from the nozzle fixing member 105.
07. Note that a broken line 108 is a mold accommodating space.

In order to manufacture a bent pipe joint using such a conventional injection molding apparatus, a mold having a cylindrical molding cavity corresponding to the shape of the manufactured bent pipe joint is used. The molten resin is injected into the molding cavity of the shape from at least one circumferential position and solidified. In this case, the injected resin is branched in two directions in the molding space, flows in the circumferential direction, merges and solidifies in a cylindrical shape. In addition, a joint generally called a perching line is formed at a portion where the resins have joined.

According to this method, when the product weight is less than 1 kg at the maximum, there is not much problem. Also, the time per one shot is efficient. Non-parallel curved surface products are also elegantly finished. The unmanned operation that is optimal for mass production can be designed and implemented relatively easily. It has the advantage that it can be commercialized in one shot by the development of mold technology.

On the other hand, when manufacturing a large-sized pipe joint having a diameter of 20 cm or more, a problem in strength occurs due to the above-described seam. Therefore, the manufactured bent pipe joint is cut along its length direction. Generally, a method of separately manufacturing a pair of divided pieces having the same shape as that obtained by dividing into two pieces and bonding the divided pieces to each other is adopted.

[0007]

According to the former method described above, the above-mentioned seam causes the strength of the bent joint to decrease. As a result, the strength of the bent pipe joint portion is reduced by about 35% from the strength of a normal pipe to be constructed. This drop in strength cannot be corrected with current molding technology.

In the latter method described above, since the divided bent pipe joint pieces must be bonded, the number of steps is increased, and the strength of the joint is also inferior.

[0009] On the other hand, molding methods that do not produce a joint or a seam have been attempted. For example, if resin is injected from one end in the axial direction into a cylindrical molding cavity corresponding to the shape of a curved joint to be manufactured, the resin moving angular velocity at the inside and outside of the curved portion of the molding cavity is changed. In other words, the resin supply speed of the outer portion is lower than that of the inner portion, so that the outer and inner portions of the bent portion of the bent pipe joint may have different wall thicknesses. In extreme cases, the outer portion may have holes due to the small thickness. This becomes increasingly more pronounced with larger pipe diameters.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for blow molding a seamless bent pipe joint having a predetermined curvature.

[0011]

According to the present invention, in a method of manufacturing a bent pipe joint by extruding a kneaded thermoplastic resin and by blow molding, a method of manufacturing an inner nozzle surface continuous in a circumferential direction and the inner nozzle surface is performed. Also has an annular nozzle hole defined by an outer nozzle surface which is continuous in the circumferential direction.
In addition, a nozzle member is provided in which a distance between the inner nozzle surface and the outer nozzle surface is partially different in a circumferential direction, and a female mold having a sealable molding cavity shaped according to the outer shape of the bent pipe joint. Preparing the tubular intermediate product by extruding the kneaded thermoplastic resin from the one end in the axial direction through the nozzle hole, and enclosing the tubular intermediate product in the molding space to form the tubular intermediate product. A blow molding method is provided, comprising supplying a compressed fluid to the inside and pressing the tubular intermediate product against the wall of the molding cavity.

According to the present invention, in the blow molding method, a male mold is inserted into both ends of the tubular intermediate product in the tube axis direction, and a gap is formed between the both ends and the wall of the molding cavity. And pressurizing the both ends against the male mold by supplying a compressed fluid.

According to the present invention, in the blow molding method, the tubular intermediate product is bent in accordance with the bent joint, and a distance between the inner nozzle surface and the outer nozzle surface is set as the nozzle member. A blow molding method is characterized in that a wider one is used on the opposite side as compared to the side that matches the direction of bending of the intermediate product.

According to the present invention, in the blow molding method, the tubular intermediate product is bent in accordance with the bent joint, and the inner nozzle surface and the outer nozzle surface are similar to each other as the nozzle member. A blow molding method characterized by using one that is eccentric with respect to the inside nozzle surface on the side that matches the direction of bending of the tubular intermediate product is obtained.

According to the present invention, in the blow molding method, the tubular intermediate product is bent in accordance with the bent joint, and the bent pipe joint has a uniform thickness in a circumferential direction and a circular cross section. The blow molding method is characterized in that the inner nozzle surface and the outer nozzle surface both have a circular shape.

Further, according to the present invention, in an apparatus for manufacturing a bent pipe joint by extruding a kneaded thermoplastic resin by blow molding, an inner nozzle surface continuous in a circumferential direction and a circumferentially outer portion of the inner nozzle surface outside the inner nozzle surface. A nozzle member having an annular nozzle hole defined by a continuous outer nozzle surface and a gap between the inner nozzle surface and the outer nozzle surface being partially different in a circumferential direction; A blow molding apparatus is obtained, comprising: extrusion means for extruding through a nozzle hole to form a tubular intermediate product; and blow molding means for blowing the tubular intermediate product.

According to the present invention, in the blow molding apparatus, the blow molding means has a molding cavity having a shape according to the outer shape of the curved pipe joint, and the tubular intermediate product is placed in the molding cavity. A female mold to be accommodated, two male molds respectively inserted into both ends of the tubular intermediate product in the tube axial direction accommodated in the molding cavity, and both ends of the tubular intermediate product in the tube axial direction facing radially outward. First biasing means for biasing each of the
A second urging means for urging the intermediate portion in the pipe axial direction of the tubular intermediate product inward in the radial direction, respectively, to obtain a blow molding apparatus.

According to the present invention, in the blow molding apparatus, when the tubular intermediate product is extruded through the nozzle hole, the tubular intermediate product is bent according to the bent joint, and the nozzle member is connected to the inner nozzle surface. A blow molding apparatus is characterized in that the distance from the outer nozzle surface is wider on the opposite side than the side coincident with the bending direction of the tubular intermediate product.

According to the present invention, in the blow molding apparatus, when the tubular intermediate product is extruded through the nozzle hole, the tubular intermediate product is bent in accordance with the bent pipe joint, and the nozzle member is connected to the inner nozzle surface. A blow molding apparatus characterized in that an outer nozzle surface and an outer nozzle surface are similar to each other, and the inner nozzle surface is eccentric with respect to the outer nozzle surface on a side corresponding to a bending direction of the tubular intermediate product. can get.

According to the present invention, in the blow molding apparatus, the bent pipe joint has a uniform thickness in a circumferential direction and a circular cross section, and the nozzle member includes the inner nozzle surface and the inner nozzle surface. A blow molding apparatus is obtained in which the outer nozzle surfaces are all shaped according to a circle.

[0021]

According to the blow molding method of the present invention, the inner nozzle surface continuous in the circumferential direction and the outer nozzle surface outside the inner nozzle surface,
A nozzle member having an annular nozzle hole defined by an outer nozzle surface continuous in a circumferential direction, and further comprising a nozzle member in which a distance between the inner nozzle surface and the outer nozzle surface is partially different in a circumferential direction; A female mold having a sealing cavity capable of being sealed according to the outer shape of the pipe joint is prepared, and the kneaded thermoplastic resin is extruded from one end in the axial direction through the nozzle hole to form a tubular intermediate product. The kneaded thermoplastic resin is filled by enclosing the tubular intermediate product in a cavity and supplying a compressed fluid to the inside of the tubular intermediate product to press the tubular intermediate product against the wall of the molding cavity. Is extruded and a bent pipe joint is manufactured by blow molding.

In the blow molding apparatus according to the present invention, the nozzle member has an annular shape defined by an inner nozzle surface that is continuous in the circumferential direction and an outer nozzle surface that is circumferentially continuous outside the inner nozzle surface. It has a nozzle hole, and the interval between the inner nozzle surface and the outer nozzle surface is partially different in the circumferential direction. Extrusion means extrudes the kneaded thermoplastic resin through the nozzle hole to produce a tubular intermediate product. The blow molding means blow-molds the tubular intermediate product to produce a bent pipe joint from the kneaded thermoplastic resin.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A is a perspective view showing a bent pipe joint manufactured according to an embodiment of the present invention, and FIG. 1B is a sectional view of the bent pipe joint shown in FIG. As shown in FIGS. 1 (a) and 1 (b), a curved pipe joint 1 according to an embodiment of the present invention is an integrally molded product made of hard vinyl chloride, and has a pair of annular opening surfaces at both ends perpendicular to each other. , And a bent portion 3 having an annular cross-section for connecting these bent portions 2 and 2 by bending them. The wall thickness of this bent pipe joint 1 is 2
Both are formed equally. The outer wall 4 and the inner wall 5 along the curve also have the same thickness. Also, as shown in FIG. 1B, the inner diameter d of the bent portion 3 is smaller than the inner diameter D of the receiving portion 2, and the inner diameter D of the receiving portion 2 is equal to the outer diameter of the bent portion 3. Hole 6 is stepped at these boundaries.

FIGS. 2A, 2B, and 2C are views showing a main part of a bending pipe joint forming apparatus according to an embodiment of the present invention, and FIG. 2 (b) is a front view of the extrusion nozzle member 15, and FIG. 2 (c) is a cross-sectional view of a blow molding die. FIG. 3 is a front view of the extrusion nozzle member of FIG. 2B.

2 (a) and 2 (b), the blow molding apparatus includes an extrusion unit 10 and a molding die 20. The extruding section 10 includes a nozzle member 15 and extruding means for extruding the kneaded thermoplastic resin through the nozzle member 15. Specifically, the extruding section 10 includes a hollow section 11 having an annular cross section, a screw section 13 inserted into the resin storage section 12 of the hollow section 11, and one end of the hollow section 11. A rectangular disk-shaped resin extrusion nozzle member 15 provided to seal the body 11 is provided. The cavity 11 and the screw 13 together constitute an extruding means.

The screw section 13 of the extruding section 10 is a screw used for ordinary extrusion molding. Due to the rotational force of the screw part 13 of the extrusion part, the nozzle hole 19 of the nozzle member 15
Extrudes a tubular intermediate product made of resin, which is a bent pipe joint.

The nozzle member 15 includes a nozzle outer die 16 forming an outer nozzle surface 16a, and a nozzle inner die 17 forming an inner nozzle surface 17a having a similar cross section to the outer nozzle surface 16a. The nozzle member 15 has an annular nozzle hole 19 extending from the tip to the inside of the cavity 11 at the other end of the nozzle member 15. This nozzle hole 19 is
The nozzle inner mold 1 gradually moves to the cavity 11 side.
7 is formed so that the cross-sectional area of the outer peripheral surface is gradually reduced so that the cross-sectional area of the nozzle hole is gradually increased. As shown in FIG. 3, this nozzle member 15 has a large width 19a at a portion corresponding to the outside of this curve in a bent molding cavity of a molding die 20 described later, and is provided inside the hole of the die. A position where the center of the circular cross section of the inner nozzle surface 17a of the nozzle inner die 17 is eccentric with respect to the center of the circular cross section of the outer nozzle surface 16a of the nozzle outer die 16 so that the width 19b of the corresponding portion becomes smaller. And an eccentric annular nozzle hole 19 is formed. Therefore, in the drawing, the width of the nozzle hole 19 gradually decreases from the upper part to the lower part as it moves in the circumferential direction. In addition, this nozzle hole 1
9 is provided with a gate (not shown) for blocking resin extrusion. In the drawing, the broken line 17 'indicates the position of the conventional nozzle inner mold.

In FIG. 2C, the blow molding die 2
0 indicates that both ends of the bent molding cavity 22 of the female mold 21 are sealed by a pair of male dies 23 and 24, and that one of the male mold 23 and the female mold 21 has the inside of the molding cavity 22. As described later, an air injection hole for introducing high-pressure air as first and second urging means is provided. That is, the male molds 23 and 24 have the tip portions 23a and 24a inserted into the molding cavity 22 projecting in a hemispherical shape, and subsequently the cylindrical portions having the shapes along the both end portions 22a and 22b of the hole 22. 23a, 24a and further lids 23c, 24c are provided integrally, and both ends of the molding cavity 22 are sealed by inner surfaces 23d, 24d of the lids. Also, from the outer end surface of the lid 23c of one male mold 23 to the tip 23
The air injection hole 23e penetrates to a. Further, the male mold 24 is not provided with an air injection hole. Extrusion unit 10
And the blow molding die 20 sandwiches the tubular intermediate product extruded from the nozzle member 15, and inserts the male dies 23 and 24 into the sleeve portion. High-pressure air, which is the first urging means, is injected into both ends of the product in the tube axis direction from the air injection holes 23e, and the resin injected into the mold with this pressure is brought into close contact with the product to produce a blow-molded product with high accuracy. Things.

FIG. 4 is a view showing a small female die of the blow molding die shown in FIG. 2 (c). As shown in FIG.
It is formed from a pair of small female molds 20a that are divided into two and overlap each other along two axes. The small female mold 20a
A semicircular die 25 having a semicircular cross section in a semicylindrical groove having a circular cross section,
26 and an arc die 27 having an inner diameter smaller than these dies 25 and 26 and forming an arc in the length direction are inserted through a rubber packing 28. The small female mold 20a has a molding cavity 22 extending from the outside to both ends in the axial direction.
a, 22b are provided with continuous air injection holes 25a and 26a, respectively. The female mold 20 is formed by fitting and fixing the small female mold 20a and another symmetrically-formed small female mold cavity (not shown). The rubber packing 28 is used for sealing when the small female molds are overlapped.

Next, a method of manufacturing a bent pipe joint by the manufacturing apparatus according to the embodiment of the present invention will be described. First, FIG.
With reference to (a), (b), and (c), a resin tubular intermediate product is extruded from the nozzle member 15 in a state where both the male dies 23 and 24 are pulled out from the female die 20. The tip of the extruded tubular intermediate product is received by one male mold 23, and the end of the tubular intermediate product is sealed by the other male mold 24. This tubular intermediate product is sandwiched between a pair of female dies 20a from both sides and inserted into the molding cavity 22. High-pressure air, which is the first urging means, is injected into the resin tubular intermediate product from the air injection hole 23e of the male mold 24. Then, the resin is brought into pressure contact with the wall of the molding cavity 22 so as to maintain the same thickness at all portions, and the bent portion 3 of the bent pipe joint is formed (see FIG. 1).
While maintaining this pressure, high-pressure air is injected from the air injection holes 25a, 25a as second urging means.
The resin at both ends of the tube shaft of the tubular intermediate product in 2a is pressed against the outer peripheral surfaces of the male cylindrical portions 23b and 24b, so that a uniform curved surface is formed on the inner surface, a step is formed, and the receiving portion is formed. 2 is completed. In this blow molding method, the resin is not expanded but reduced by pressure, so that the density of the molded product can be increased, the product strength can be increased, and the accuracy of the product can be enhanced.

In the embodiments of the present invention, hard vinyl chloride is used as the thermoplastic resin.
For example, the present invention can be applied to a polyethylene resin, a nylon resin, and the like.

[0033]

As described above, according to the present invention, the blow molding of a seamless curved pipe joint having a bent portion having a predetermined curvature and receiving portions at both ends of the bent portion. Methods and apparatus can be provided.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a bent pipe joint manufactured according to an embodiment of the present invention. (B) is sectional drawing of the bent pipe joint of (a).

FIG. 2 (a) is a cross-sectional view illustrating an extruded portion of a blow molding device for a bent pipe joint according to an embodiment of the present invention. (B) is a front view of the nozzle member of (a). (C) is sectional drawing which shows the shaping | molding die of the blow-molding apparatus of the curved pipe joint which concerns on the Example of this invention.

FIG. 3 is an enlarged front view of the nozzle member of FIG. 2 (b).

FIG. 4 is a view showing a blow molding die of FIG. 2 (c).

FIG. 5 is a partial cross-sectional view showing one structural example of a conventional injection molding apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 curved pipe joint 2 receiving part 3 bent part 4 outer wall 5 inner wall 10 extrusion part 11 cavity part 12 resin storage part 13 screw part 15 nozzle member 16 nozzle outer mold 17 nozzle inner mold 19 nozzle hole 20 metal for blow molding Mold 21 female mold 22 molding cavity 23,24 male mold 23e, 25a air injection hole 25,26 semicircle die 27 arc die 28 rubber packing 101 cavity 102 screw part 103 drive source 104 hopper 105 nozzle fixing member 106 gold Mold fixing member 107 Rod 110 Nozzle member

Claims (10)

(57) [Claims] 1. A method for manufacturing a bent pipe joint by extruding a kneaded thermoplastic resin and blow molding, wherein an inner nozzle surface which is continuous in a circumferential direction and an outer surface which is outer than the inner nozzle surface and which is continuous in a circumferential direction. A nozzle member having an annular nozzle hole defined by a nozzle surface and having a gap between the inner nozzle surface and the outer nozzle surface that is partially different in a circumferential direction; Preparing a female mold having a sealable molding cavity of a shape according to the above, extruding the kneaded thermoplastic resin through the nozzle hole from one end in the axial direction to form a tubular intermediate product;
And enclosing the tubular intermediate product in the molding cavity, supplying a compressed fluid to the inside of the tubular intermediate product, and pressing the tubular intermediate product against the wall of the molding cavity. Blow molding method. 2. The blow molding method according to claim 1, wherein male molds are inserted into both ends of the tubular intermediate product in the tube axis direction, and between the both ends and the wall of the molding cavity. Supplying a compressed fluid to press the both ends against the male mold. 3. The blow molding method according to claim 1, wherein the tubular intermediate product is bent in accordance with the bending joint, and a distance between the inner nozzle surface and the outer nozzle surface as the nozzle member is the tubular shape. A blow molding method characterized by using an intermediate product that is wider on the side opposite to the side that matches the bending direction of the intermediate product. 4. The blow molding method according to claim 1, wherein the tubular intermediate product is bent in accordance with the bending joint, and the inner nozzle surface and the outer nozzle surface are similar to each other as the nozzle member. A blow molding method characterized by using an inner nozzle surface which is eccentric with respect to a side corresponding to a bending direction of the tubular intermediate product. 5. The blow molding method according to claim 4, wherein the tubular intermediate product is bent according to the bent joint, and the bent pipe joint has a uniform thickness in a circumferential direction and a circular cross section. Wherein the inner nozzle surface and the outer nozzle surface both have a circular shape. 6. An apparatus for manufacturing a bent pipe joint by extruding a kneaded thermoplastic resin by blow molding, comprising: an inner nozzle surface continuous in a circumferential direction; and an outer nozzle surface continuous in a circumferential direction outside the inner nozzle surface. A nozzle member having an annular nozzle hole defined by the formula, wherein the interval between the inner nozzle surface and the outer nozzle surface is partially different in the circumferential direction, and the kneaded thermoplastic resin is extruded through the nozzle hole to form a tube. A blow molding apparatus, comprising: extrusion means for producing an intermediate product; and blow molding means for blowing the tubular intermediate product. 7. A blow molding apparatus according to claim 6, wherein said blow molding means has a molding cavity having a shape according to the outer shape of said curved pipe joint, and stores said tubular intermediate product in said molding cavity. A female mold to be accommodated, two male molds respectively inserted into both ends of the tubular intermediate product in the tube axial direction accommodated in the molding cavity, and both ends of the tubular intermediate product in the tube axial direction facing radially outward. And a second urging means for urging the intermediate portion of the tubular intermediate product in the pipe axial direction radially inward. 8. The blow molding apparatus according to claim 6, wherein when the tubular intermediate product is extruded through the nozzle hole, the tubular intermediate product is bent in accordance with the bent joint, and the nozzle member is connected to the inner nozzle surface. A blow molding apparatus, wherein a distance from the outer nozzle surface is wider on a side opposite to a direction corresponding to a bending direction of the tubular intermediate product. 9. The blow molding apparatus according to claim 6, wherein said tubular intermediate product is bent in accordance with said bent pipe joint when being extruded through said nozzle hole, and said nozzle member is provided between said inner nozzle surface and said inner nozzle surface. A blow molding apparatus, wherein an outer nozzle surface is similar to each other, and the inner nozzle surface is eccentric with respect to the outer nozzle surface on a side corresponding to a bending direction of the tubular intermediate product. 10. The blow molding apparatus according to claim 6, wherein the bent pipe joint has a uniform thickness in a circumferential direction and a circular cross section, and the nozzle member includes the inner nozzle face and the inner nozzle face. A blow molding apparatus, wherein each of the outer nozzle surfaces has a circular shape.