Plastic Pipe

Abstract

To provide a resin pipe that suppresses a bending phenomenon and narrows the width of a connecting portion, in the resin pipe in which a first resin pipe and a second resin pipe are coupled by the connecting portion by a blow molding method.SOLUTION: A breather pipe 3 (first resin pipe) and a filler pipe 2 (second resin pipe) have a breather pipe vertical side part 6 (first resin pipe vertical side part) coupled with a connecting portion 4, and a filler pipe vertical side part 5 (second resin pipe vertical side part) of length equal to or longer than the breather pipe vertical side part 6. The filler pipe 2 has a generally straight filler pipe upper line part 7 (second resin pipe upper line parts) and a filler pipe lower line part 8 (second resin pipe lower line part) extending from both end parts of the filler pipe vertical side part 5 in the opposite direction to the connecting portion 4 side. The filler pipe upper line part 7 and the filler pipe lower line part 8 are expanded as it separates from the filler pipe vertical side part 5.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a resin pipe formed by integrally molding a first resin pipe and a second resin pipe having a larger cross-sectional area than the first resin pipe at a connection part by a blow molding method. [Background technology]

[0002] 10, a molding method has been proposed for a resin pipe 1 in which a breather pipe 3, which is a first resin pipe with a substantially rectangular cross section, and a filler pipe 2, which is a second resin pipe with a substantially rectangular cross section and a cross-sectional area larger than that of the breather pipe 3, are connected to each other via a connecting part 4 and molded integrally (for example, Patent Document 1). Also known is a resin pipe 1 in which a breather pipe 3 and a filler pipe 2, both of which have circular cross sections, are connected to each other via a connecting part 4 and molded integrally.

[0003] The resin pipe 1 of Patent Document 1 is manufactured as follows. As shown in Fig. 11, the upper mold 20 and the lower mold 30 of the blow molding die 15 are opened, and the parison 11 is introduced between them. The parison 11 is placed in the lower mold first cavity 31 and the lower mold second cavity 32.

[0004] At this time, the lower die slide core 33 separating the lower die first cavity 31 and the lower die second cavity 32 retreats from the cavity surface, and the lower die first cavity 31 and the lower die second cavity 32 become one cavity. Similarly, the upper die slide core 23 separating the upper die first cavity 21 and the upper die second cavity 22 retreats from the cavity surface, and the upper die first cavity 21 and the upper die second cavity 22 become one cavity.

[0005] Next, as shown in Figure 12, when the upper mold 20 and the lower mold 30 are closed, the upper mold slide core 23 and the lower mold slide core 33 remain retracted from the cavity surface, so that the parison 11 is positioned within a single cavity formed by the upper mold first cavity 21 and the upper mold second cavity 22, and the lower mold first cavity 31 and the lower mold second cavity 32.

[0006] Next, as shown in FIG. 13, the upper mold slide core 23 and the lower mold slide core 33 are inserted into their respective cavities, and the parison 11 in the cavities is subjected to a primary blow, so that the parison 11 can be abutted against the upper mold first cavity 21 and the upper mold second cavity 22, and the lower mold first cavity 31 and the lower mold second cavity 32.

[0007] 14, the upper slide core 23 and the lower slide core 33 are each further inserted into the cavity, and a secondary blow is performed on the parison 11. This secondary blow makes it possible to mold the resin pipe 1 in which the filler pipe 2 and the breather pipe 3, which have been molded into a predetermined shape, are connected at the connection part 4. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2016-107488 A Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, in the primary blow in FIG. 13, the parison 11 is in contact with the upper die 20 and the lower die 30 of the blow molding die 15, the upper die slide core tip portion 26 of the upper die slide core 23, and the lower die slide core tip portion 36 of the lower die slide core 33, but is not in contact with the upper die slide core recess 25 and the lower die slide core recess 35.

[0010] Therefore, in the primary blow, as shown in Fig. 15, the parison 11 may enter into the gap between the upper die slide core recess 25, the lower die slide core recess 35, and the upper die 20 and the lower die 30 of the blow molding die 15, causing a so-called folding phenomenon. This folding phenomenon causes the parison 11 to become thin-walled at the corners between the parison 11 and the upper die 20 and the lower die 30 of the blow molding die 15, or at the corners between the parison 11 and the upper die slide core tip 26 and the lower die slide core tip 36, and in the worst case, causes the resin pipe 1 to break in the subsequent secondary blow. In particular, this folding phenomenon is likely to occur when the upper die slide core recess 25 and the lower die slide core recess 35 are deep, or when the radius of the upper die slide core recess 25 and the lower die slide core recess 35 is large.

[0011] On the other hand, there is a demand for narrowing the connection portion 4 between the filler pipe 2 and the breather pipe 3 to reduce the space required, the weight, and the cost.

[0012] Therefore, the present invention provides a resin pipe in which a first resin pipe and a second resin pipe having a larger cross-sectional area than the first resin pipe are connected at a connection part by a blow molding method to be integrally molded, which suppresses the above-mentioned folding phenomenon and has a narrower width at the connection part. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention of claim 1 provides a resin pipe in which a first resin pipe and a second resin pipe having a cross-sectional area larger than that of the first resin pipe are connected at a connection portion by a blow molding method to be integrally molded, wherein in a cross section, the first resin pipe and the second resin pipe have a first resin pipe vertical side portion connected to the connection portion and a second resin pipe vertical side portion having a length equal to or greater than that of the first resin pipe vertical side portion, and the second resin pipe has a second resin pipe upper line portion and a second resin pipe lower line portion which are substantially straight and extend from both end portions of the second resin pipe vertical side portion in a direction opposite to the connection portion side, the first resin pipe has a first resin pipe upper line portion and a first resin pipe lower line portion which are substantially straight and extend from both end portions of the first resin pipe vertical side portion in a direction opposite to the connection portion side, The upper line of the second resin pipe and the lower line of the second resin pipe widen as they move away from the vertical side of the second resin pipe. The upper line portion of the first resin pipe and the lower line portion of the first resin pipe are formed on a line extending from the upper line portion of the second resin pipe and the lower line portion of the second resin pipe to the first resin pipe side. The resin pipe is characterized by the above.

[0014] The present invention of claim 1 provides a resin pipe formed integrally by connecting a first resin pipe and a second resin pipe having a cross-sectional area larger than that of the first resin pipe at a connection portion by a blow molding method, the first resin pipe and the second resin pipe having, in cross section, a first resin pipe vertical side portion connected to the connection portion and a second resin pipe vertical side portion having a length equal to or greater than that of the first resin pipe vertical side portion, the second resin pipe having a second resin pipe upper line portion and a second resin pipe lower line portion which are substantially straight and extend from both end portions of the second resin pipe vertical side portion in a direction opposite to the connection portion side, the first resin pipe has a first resin pipe upper line portion and a first resin pipe lower line portion which are substantially straight and extend from both end portions of the first resin pipe vertical side portion in a direction opposite to the connection portion side, The upper line of the second resin pipe and the lower line of the second resin pipe widen as they move away from the vertical side of the second resin pipe. The upper line portion of the first resin pipe and the lower line portion of the first resin pipe are formed on a line extending from the upper line portion of the second resin pipe and the lower line portion of the second resin pipe to the first resin pipe side. Therefore, while maintaining the cross-sectional area of ​​the second resin pipe, the length of the vertical side portion of the second resin pipe can be made shorter than before (at the same time, the length of the vertical side portion of the first resin pipe is also made shorter than before), and the height of the slide core recesses on the first resin pipe side and the second resin pipe side can be made smaller, i.e., the slide core recesses can be molded shallower.

[0015] As a result, the gap between the slide core recess and the upper and lower dies during the primary blow becomes smaller, making it possible to suppress the occurrence of the folding phenomenon.

[0016] In addition, the two approximately straight lines above and below include not only straight lines but also slight arc shapes, and include cases where both the top and bottom are straight lines, one is straight and the other is slightly arc-shaped, and both the top and bottom are slightly arc-shaped.

[0020] Claim 2 The present invention relates to Claim 1 In the invention, at least one of the first resin pipe vertical side portion and the second resin pipe vertical side portion is a resin pipe that is connected to the connection portion approximately perpendicularly.

[0021] The above Claim 1 According to the invention, the height of the upper and lower slide core recesses is reduced, so that the amount of movement (penetration) of the slide core can be reduced. As a result, the film thickness of the python can be maintained uniform even if the radius of the slide core recess is reduced.

[0022] Claim 2 In the present invention, First resin pipe vertical side At least one of the first and second resin pipe vertical sides is a resin pipe that is connected to the connecting part approximately perpendicularly, so the width of the slide core can be reduced to mold the resin pipe, and the width of the connecting part can be narrowed. As a result, the resin pipe can be made lighter, take up less space, and cost can be reduced. The approximately perpendicular shape is determined by taking into account the draft angle when the mold is opened up and down after molding.

[0023] Claim 3 The present invention relates to claim 1 or Claim 2 In the invention, the connection portion is a resin pipe that connects the first resin pipe vertical side portion and the second resin pipe vertical side portion near the center thereof.

[0024] Claim 3 In the present invention, since the connecting portion is a resin pipe that connects the first resin pipe vertical side portion and the second resin pipe vertical side portion near the center portion, the slide core recess can be almost evenly supported by the upper and lower slide cores. As a result, the height of the slide core recess on the first resin pipe side and the second resin pipe side can be reduced, i.e., the slide core recess can be molded shallow, so that the gap between the slide core recess and the upper and lower dies in the primary blow is further reduced, and the occurrence of the folding phenomenon can be further suppressed.

[0025] Claim 4 The present invention is as follows: 3 In the invention of the first resin The pipe is a breather pipe and the second resin The pipe is a plastic pipe that is a filler pipe.

[0026] Claim 4 In the present invention, First resin pipe is the breather pipe, and the second resinSince the pipe is a resin pipe which is a filler pipe, the breather pipe can be formed integrally along the filler pipe, the breather pipe can be firmly attached to the filler pipe, and the filler pipe and the breather pipe can be easily attached to the vehicle body. Effect of the Invention

[0027] A resin pipe formed by connecting a first resin pipe and a second resin pipe having a cross-sectional area larger than that of the first resin pipe at a connection portion by a blow molding method, the first resin pipe and the second resin pipe having, in a cross section, a first resin pipe vertical side portion connected to the connection portion and a second resin pipe vertical side portion having a length equal to or longer than that of the first resin pipe vertical side portion, the second resin pipe having a second resin pipe upper line portion and a second resin pipe lower line portion which are substantially straight and extend from both end portions of the second resin pipe vertical side portion in a direction opposite to the connection portion side, the first resin pipe has a first resin pipe upper line portion and a first resin pipe lower line portion which are substantially straight and extend from both end portions of the first resin pipe vertical side portion in a direction opposite to the connection portion side, The upper line of the second resin pipe and the lower line of the second resin pipe widen as they move away from the vertical side of the second resin pipe. The upper line portion of the first resin pipe and the lower line portion of the first resin pipe are formed on a line extending from the upper line portion of the second resin pipe and the lower line portion of the second resin pipe to the first resin pipe side. Therefore, while maintaining the cross-sectional area of ​​the second resin pipe, the length of the vertical side portion of the second resin pipe can be made shorter than before (at the same time, the length of the vertical side portion of the first resin pipe is also made shorter than before), and the height of the slide core recesses on the first resin pipe side and the second resin pipe side can be made smaller, i.e., the slide core recesses can be molded shallower.

[0028] As a result, the gap between the slide core recess and the upper and lower dies during the primary blow becomes smaller, making it possible to suppress the occurrence of the folding phenomenon. [Brief description of the drawings]

[0029] [Figure 1] FIG. 2 is a front view of a resin pipe molded according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the resin pipe molded in the first embodiment of the present invention, taken along the line AA in FIG. [Diagram 3]FIG. 2 is a cross-sectional view showing a state in which the blow molding die used in the first embodiment of the present invention is opened and a parison is placed between the blow molding halves. [Figure 4] FIG. 2 is a schematic diagram showing a state of a slide core and a parison in a state where the blow molding die used in the first embodiment of the present invention is closed and the parison is placed between the blow molding halves. [Diagram 5] FIG. 2 is a schematic diagram showing the state of the blow molding die, the slide core, and the parison when the upper and lower slide cores of the blow molding die used in the first embodiment of the present invention are inserted into the cavity to perform the primary blow. [Figure 6] FIG. 2 is a schematic diagram showing the state of the blow molding die, the slide core, and the parison when the upper and lower slide cores of the blow molding die used in the first embodiment of the present invention are further inserted into the cavity to perform a secondary blow. [Figure 7] 2 is a cross-sectional view of a resin pipe molded in a second embodiment of the present invention, taken along line AA in FIG. 1. [Figure 8] FIG. 11 is a schematic diagram showing the state of the blow molding die, the slide core, and the parison when the upper and lower slide cores of the blow molding die used in the second embodiment of the present invention are inserted into the cavity to perform the primary blow. [Figure 9] FIG. 11 is a schematic diagram showing the state of the blow molding die, the slide core, and the parison when the upper and lower slide cores of the blow molding die used in the second embodiment of the present invention are further inserted into the cavity to perform a secondary blow. [Figure 10] FIG. 1 is a cross-sectional view of a conventional resin pipe (Patent Document 1). [Figure 11] FIG. 1 is a cross-sectional view of a conventional blow molding die that is opened and a parison is placed between the blow molding halves (Patent Document 1). [Figure 12] FIG. 1 is a schematic diagram showing a state of a slide core and a parison when a conventional blow molding die is closed and a parison is placed between the blow molding halves (Patent Document 1). [Figure 13]FIG. 1 is a schematic diagram showing the state of a blow molding die, a slide core, and a parison when the upper and lower slide cores of a conventional blow molding die are inserted into a cavity to perform a primary blow (Patent Document 1). [Figure 14] FIG. 1 is a schematic diagram showing the state of a blow molding die, a slide core, and a parison when the upper and lower slide cores of a conventional blow molding die are further inserted into the cavity to perform a secondary blow (Patent Document 1). [Figure 15] FIG. 14 is an enlarged schematic view of the vicinity of the slide core in FIG. 13, explaining the occurrence of the folding phenomenon of the parison. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] First and second embodiments of the present invention will be described with reference to Fig. 1 to Fig. 10. The second embodiment will be described later. As an example of a resin pipe 1 molded by blow molding of the present invention, a resin pipe 1 in which a filler pipe 2 and a breather pipe 3 are connected to each other by a connection part 4 and molded as one piece by a blow molding method for supplying fuel to a fuel tank from a fuel filler port of an automobile body will be described. However, the present invention can also be used for other blow molded resin pipes in which a first resin pipe and a second resin pipe having a larger cross-sectional area than the first resin pipe are connected to each other by a connection part and molded as one piece, which are bent three-dimensionally.

[0031] Fig. 1 is a front view of a resin pipe 1 molded by a blow molding method according to a first embodiment of the present invention, and Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. The resin pipe 1 is formed by bending three-dimensionally along the shape of an automobile body, and is composed of a filler pipe 2 which is a hollow second resin pipe, a breather pipe 3 which is a hollow first resin pipe formed along the filler pipe 2 and has a smaller cross-sectional area than the filler pipe 2, and a plate-shaped connecting part 4 which integrally connects the filler pipe 2 and the breather pipe 3. As shown in Fig. 1, the filler pipe 2 and the breather pipe 3 communicate with each other at their tips.

[0032] 2, the filler pipe 2 is formed with a filler pipe vertical side portion 5 which is a vertical side portion of the second resin pipe, and is formed with a filler pipe upper line portion 7 which is a substantially straight line portion of the second resin pipe extending from both end portions of the filler pipe vertical side portion 5 in the opposite direction to the connection portion 4 side, and a filler pipe lower line portion 8 which is a substantially straight line portion of the second resin pipe. In addition, the filler pipe vertical side portion 5 is vertically connected to the connection portion 4 at approximately the center of the filler pipe vertical side portion 5.

[0033] On the other hand, the breather pipe 3 also has a breather pipe vertical side portion 6, which is a vertical side portion of the first resin pipe, and the breather pipe vertical side portion 6 is vertically connected to the connection portion 4 at approximately the center of the breather pipe vertical side portion 6. The cross-sectional areas of the hollow portions of the filler pipe 2 and the breather pipe 3 are the same as those of the conventional one (FIG. 10).

[0034] In addition, in FIG. 2, the filler pipe vertical side portion 5 and the breather pipe vertical side portion 6 have a slight inclination in the vertical direction relative to the connection portion 4. This is a draft angle that is used when opening the upper mold 20 and the lower mold 30 of the blow molding die 15 described later after molding the resin pipe 1 and removing the product, and this slight inclination is included in the vertical category.

[0035] The breather pipe 3 also has a first resin portion extending substantially linearly from both ends of the vertical side portion 6 of the breather pipe. pipe The upper wire portion is a breather pipe upper wire portion 9 and a first resin pipe A breather pipe lower line portion 10, which is a lower line portion, is formed in the opposite direction to the connection portion 4. In Fig. 2, the breather pipe upper line portion 9 and the breather pipe lower line portion 10 are formed on a line extending the filler pipe upper line portion 7 and the filler pipe lower line portion 8 toward the breather pipe 3. That is, the cross section of the resin pipe 1 has a shape in which two substantially straight lines, one above the other, extending from the breather pipe 3 to the filler pipe 2 toward the filler pipe 2 are narrowed substantially vertically near the connection portion.

[0036] Since the resin pipe 1 has the shape shown in FIG. 2, the lengths of the filler pipe vertical side portion 5 and the breather pipe vertical side portion 6 are shorter than those in FIG.

[0037] The side opposite to the connection part 4 of the filler pipe 2 and the breather pipe 3 is formed in an arc shape. However, this is not limited to an arc shape. The filler pipe lower line part 8 and the breather pipe lower line part 10 are formed substantially parallel to the connection part 4, and the filler pipe upper line part 7 is formed so as to widen as it moves away from the connection part 4 side. The filler pipe upper line part 7 may be formed substantially parallel to the connection part 4, and the filler pipe lower line part 8 may be formed so as to widen toward the filler pipe 2 side, or both the filler pipe upper line part 7 and the filler pipe lower line part 8 may be formed so as to widen as it moves away from the connection part 4 side.

[0038] The manufacturing method of the present embodiment 1 will be described below. As shown in Fig. 3, the blow molding die 15 used in the first embodiment of the present invention has two blow molding split dies, an upper die 20 and a lower die 30. The upper die 20 has an upper die first cavity 21 for molding the filler pipe 2, an upper die second cavity 22 for molding the breather pipe 3, an upper die slide core 23 that slides between the upper die first cavity 21 and the upper die second cavity 22, and an upper die slide core cylinder 24 that slides the upper die slide core 23.

[0039] The lower die 30 has a lower die first cavity 31 for molding the filler pipe 2, a lower die second cavity 32 for molding the breather pipe 3, a lower die slide core 33 that slides between the lower die first cavity 31 and the lower die second cavity 32, and a lower die slide core cylinder 34 that slides the lower die slide core 33.

[0040] As described above, since the resin pipe 1 has the shape shown in FIG. 2 and the lengths of the filler pipe vertical side portion 5 and the breather pipe vertical side portion 6 are shorter than those in FIG. 10, the upper slide core recess 25 of the upper slide core 23 and the lower slide core recess 35 of the lower slide core 33 are shallower than those in FIGS. 11 to 14, and since the filler pipe upper line portion 7 and the filler pipe lower line portion 8 are made to be the filler pipe vertical side portion 5 and the breather pipe vertical side portion 6 which are narrowed almost vertically at the connection portion 4, the radius of the upper slide core recess 25 of the upper slide core 23 and the lower slide core recess 35 of the lower slide core 33 can be made smaller, and the widths of the upper slide core 23 and the lower slide core 33 are also narrowed.

[0041] First, as shown in Fig. 3, the upper mold 20 and the lower mold 30 of the blow molding die 15 are opened, and the parison 11 is introduced between them. The parison 11 is placed in the lower mold first cavity 31 and the lower mold second cavity 32. In addition, since the cross-sectional area of ​​the filler pipe 2 is larger than that of the breather pipe 3, the parison 11 is placed at a position straddling the lower mold first cavity 31, which is closer to the filler pipe 2 side, and the lower mold slide core 33.

[0042] At this time, the lower die slide core 33 separating the lower die first cavity 31 and the lower die second cavity 32 retreats from the cavity surface, and the lower die first cavity 31 and the lower die second cavity 32 become one cavity. Similarly, the upper die slide core 23 separating the upper die first cavity 21 and the upper die second cavity 22 retreats from the cavity surface, and the upper die first cavity 21 and the upper die second cavity 22 become one cavity.

[0043] Next, when the upper mold 20 and the lower mold 30 are closed, as shown in Figure 4, the upper mold slide core 23 and the lower mold slide core 33 remain retracted from the cavity surface, so that the parison 11 is positioned within a single cavity formed by the upper mold first cavity 21 and the upper mold second cavity 22, and the lower mold first cavity 31 and the lower mold second cavity 32 being integrated together.

[0044] Next, as shown in FIG. 5, the upper slide core 23 is inserted into the cavity by the upper slide core cylinder 24, and the lower slide core 33 is inserted into the cavity by the lower slide core cylinder 34, and the parison 11 in the cavity is subjected to a primary blow.

[0045] At this time, since the upper slide core recess 25 of the upper slide core 23 and the lower slide core recess 35 of the lower slide core 33 are shallower than those of the conventional ones shown in Figs. 11 to 14, it is possible to suppress the occurrence of the so-called folding phenomenon in which the parison 11 described in Fig. 15 enters into the gaps between the upper slide core recess 25, the lower slide core recess 35, and the upper die 20 and the lower die 30 of the blow molding die 15.

[0046] As a result, the parison 11 is prevented from becoming thin-walled at the corners between the parison 11 and the upper mold 20 and lower mold 30 of the blow molding die 15, and at the corners between the parison 11 and the upper mold slide core tip 26 and the lower mold slide core tip 36, and the parison 11 can be abutted with uniform thickness against the upper mold first cavity 21 and the upper mold second cavity 22 and the lower mold first cavity 31 and the lower mold second cavity 32.

[0047] Next, as shown in Fig. 6, the upper slide core 23 is advanced further into the cavity by the upper slide core cylinder 24, and the lower slide core 33 is advanced further into the cavity by the lower slide core cylinder 34. As the upper slide core 23 and the lower slide core 33 advance, a secondary blow is performed on the parison 11. At this time, the tip portions of the filler pipe 2 and the breather pipe 3 are formed to communicate with each other (Fig. 1), so that if air is blown into one of the filler pipe 2 and the breather pipe 3 during the secondary blow molding, the other resin pipe can be molded at the same time.

[0048] Furthermore, by the secondary blow, the parison 11 is sandwiched between the upper slide core tip portion 26 and the lower slide core tip portion 36 of the upper slide core 23 and the lower slide core 33 at their respective tips, forming the connection portion 4 of the resin pipe 1 and also forming the filler pipe 2 and the breather pipe 3. The primary blow suppresses the occurrence of the folding phenomenon of the parison 11 and brings it into contact with the upper die first cavity 21 and the upper die second cavity 22 and the lower die first cavity 31 and the lower die second cavity 32 with an equal thickness, so that the filler pipe 2 and the breather pipe 3 can also have an equal thickness in the secondary blow.

[0049] Finally, the upper mold 20 and the lower mold 30 of the blow molding die 15 are opened, and the molded resin pipe 1 is removed from the parison 11. This allows the resin pipe 1 in which the filler pipe 2 and the breather pipe 3 are connected at the connection part 4 to be molded in one go.

[0050] As a result, by forming the resin pipe 1 into the shape shown in FIG. 2, the upper slide core recess 25 of the upper slide core 23 and the lower slide core recess 35 of the lower slide core 33 become shallower as compared with those in FIGS. 11 to 14, and the widths of the upper slide core 23 and the lower slide core 33 can also be narrowed, so that the occurrence of the folding phenomenon can be suppressed and the connection part 4 between the filler pipe 2 and the breather pipe 3 can be narrowed, thereby enabling space saving, weight reduction and cost reduction.

[0051] Next, a second embodiment of the present invention will be described with reference to Fig. 7 to Fig. 9. The difference between the first embodiment and the second embodiment is that the cross section of the resin pipe 1 in the first embodiment has a shape in which two substantially straight lines extending from the breather pipe 3 to the filler pipe 2 at the top and bottom are narrowed near the connection part, whereas in the second embodiment, the cross section of the resin pipe 1 has a shape in which the breather pipe upper line part 9 and the breather pipe lower line part 10 of the breather pipe 3, and the filler pipe upper line part 7 and the filler pipe lower line part 8 of the filler pipe 2 are widened as they move away from the connection part 4. The cross-sectional areas of the hollow parts of the filler pipe 2 and the breather pipe 3 are the same as those of the conventional embodiment (Fig. 10) and the first embodiment (Fig. 1).

[0052] Also, like the first embodiment, the filler pipe vertical side portion 5 and the breather pipe vertical side portion 6 are formed almost perpendicularly at both ends of the connection portion 4. As a result, the lengths of the filler pipe vertical side portion 5 and the breather pipe vertical side portion 6 can be made shorter than in the first embodiment.

[0053] Also, the side opposite to the connection part 4 of the filler pipe 2 and the breather pipe 3 is formed in an arc shape. However, it is not limited to an arc shape. Also, in FIG. 7, the filler pipe upper line part 7 of the filler pipe 2 spreads out more from the connection part 4 than the filler pipe lower line part 8, but it may be reversed, or the spread may be the same. This is also true for the breather pipe upper line part 9 and the breather pipe lower line part 10 of the breather pipe 3. In FIG. 7, the spread of the breather pipe upper line part 9 and the breather pipe lower line part 10 of the breather pipe 3 from the connection part 4 is almost the same. Furthermore, one of the filler pipe upper line part 7 and the breather pipe upper line part 9, or the filler pipe lower line part 8 and the breather pipe lower line part 10 may be formed in a substantially straight line (FIG. 1) as in the first embodiment described above.

[0054] The manufacturing method of the resin pipe 1 according to the second embodiment will be described below, starting with the primary blow. As shown in Fig. 8, the upper slide core 23 is inserted into the cavity by the upper slide core cylinder 24, and the lower slide core 33 is inserted into the cavity by the lower slide core cylinder 34, and the parison 11 in the cavity is subjected to the primary blow.

[0055] At this time, since the upper slide core recess 25 of the upper slide core 23 and the lower slide core recess 35 of the lower slide core 33 are shallower than those in the first embodiment described above, it is possible to further suppress the occurrence of the so-called folding phenomenon in which the parison 11 enters into the gaps between the upper slide core recess 25, the lower slide core recess 35, and the upper die 20 and the lower die 30 of the blow molding die 15. Then, this primary blow allows the parison 11 to be brought into contact with the upper die first cavity 21 and the upper die second cavity 22 and the lower die first cavity 31 and the lower die second cavity 32 with a uniform thickness.

[0056] In addition, the breather pipe 3 and the filler pipe 2 have upper and lower approximately straight portions which widen outward as they move away from the connection portion 4, and the filler pipe upper line portion 7 and the filler pipe lower line portion 8 are formed as the filler pipe vertical side portion 5 and the breather pipe vertical side portion 6 which are narrowed approximately vertically at the connection portion 4, so that the radii of the shallower upper slide core recess 25 of the upper slide core 23 and the lower slide core recess 35 of the lower slide core 33 can be further reduced, and the widths of the upper slide core 23 and the lower slide core 33 are also narrower as compared to the first embodiment.

[0057] 9, the upper slide core 23 is further advanced into the cavity by the upper slide core cylinder 24, and the lower slide core 33 is further advanced into the cavity by the lower slide core cylinder 34. As the upper slide core 23 and the lower slide core 33 advance, the parison 11 is subjected to a secondary blow.

[0058] Furthermore, by the secondary blow, the upper slide core 23 and the lower slide core 33 sandwich the parison 11 between their tips to form the connection part 4 of the resin pipe 1, and also form the filler pipe 2 and the breather pipe 3. The primary blow prevents the parison 11 from folding, and the parison is brought into contact with the upper first cavity 21 and the upper second cavity 22 and the lower first cavity 31 and the lower second cavity 32 with an equal thickness, so that the filler pipe 2 and the breather pipe 3 can be made to have an equal thickness even in the secondary blow.

[0059] Finally, the upper mold 20 and the lower mold 30 of the blow molding die 15 are opened, and the molded resin pipe 1 is removed from the parison 11. This allows the resin pipe 1 in which the filler pipe 2 and the breather pipe 3 are connected at the connection part 4 to be molded in one go.

[0060] As a result, by forming the resin pipe 1 into the shape shown in FIG. 7, the upper slide core recess 25 of the upper slide core 23 and the lower slide core recess 35 of the lower slide core 33 become shallower as compared with those in FIGS. 11 to 14, and the widths of the upper slide core 23 and the lower slide core 33 can also be narrowed, so that the occurrence of the folding phenomenon can be further suppressed and the connection part 4 between the filler pipe 2 and the breather pipe 3 can be further narrowed, thereby enabling space saving, weight reduction and cost reduction.

[0061] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the object of the present invention.

[0062] For example, in the first embodiment, the breather pipe upper line portion 9 and the breather pipe lower line portion 10 of the breather pipe 3 are formed on a line extending from the filler pipe upper line portion 7 and the filler pipe lower line portion 8 formed on the filler pipe 2 toward the breather pipe 3 side, but as long as the length of the breather pipe vertical side portion 6 is equal to or less than the length of the filler pipe vertical side portion 5, they do not have to be on the extended line, and further, the narrowing in the opposite direction on the connection portion 4 side is not affected by the filler pipe upper line portion 7 and the filler pipe lower line portion 8 of the filler pipe 2. Furthermore, the breather pipe upper line portion 9 and the breather pipe lower line portion 10 of the breather pipe 3 may be formed in parallel. [Explanation of symbols]

[0063] 1 Plastic pipe 2 Filler pipe 3 Breather pipe 4 Connection 5 Filler pipe vertical side 6 Breather pipe vertical side 7 Filler pipe upper line 8 Filler pipe lower line 9 Breather pipe upper line 10 Breather pipe lower line 11 Parison 15 Blow mold 20 Upper mold 21 Upper mold 1st cavity 22 Upper mold 2nd cavity 23 Upper slide core 25 Upper die slide core recess 26 Upper slide core tip 30 Lower mold 31 Lower die 1st cavity 32 Lower die 2nd cavity 33 Lower slide core 35 Lower die slide core recess 36 Lower die slide core tip

Claims

1. A resin pipe in which a first resin pipe and a second resin pipe having a cross-sectional area larger than that of the first resin pipe are connected at a connection portion by a blow molding method and integrally molded, In cross section, The first resin pipe and the second resin pipe have a first resin pipe vertical side portion connected to the connection portion and a second resin pipe vertical side portion having a length equal to or longer than that of the first resin pipe vertical side portion, The second resin pipe has a second resin pipe upper line portion and a second resin pipe lower line portion which are substantially straight and extend from both end portions of the second resin pipe vertical side portion in a direction opposite to the connection portion side, The first resin pipe has a first resin pipe upper line portion and a first resin pipe lower line portion which are substantially straight and extend from both end portions of the first resin pipe vertical side portion in a direction opposite to the connection portion side, The second resin pipe upper line portion and the second resin pipe lower line portion are wider as they are separated from the second resin pipe vertical side portion, A resin pipe characterized in that the first resin pipe upper line portion and the first resin pipe lower line portion are formed on a line extending the second resin pipe upper line portion and the second resin pipe lower line portion toward the first resin pipe side.

2. The resin pipe according to claim 1 , wherein at least one of the first resin pipe vertical side portion and the second resin pipe vertical side portion is connected to the connection portion substantially perpendicularly.

3. The resin pipe according to claim 1 or 2, wherein the connection portion connects the first resin pipe vertical side portion and the second resin pipe vertical side portion near central portions thereof.

4. The resin pipe according to claim 1 , wherein the first resin pipe is a breather pipe, and the second resin pipe is a filler pipe.

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