JPH10141552A - Synthetic resin pipe provided with bellows part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic resin pipe having a bellows part structure which can be smoothly and efficiently separated from a die without damaging a bellows part, and which can be formed without requiring any intricate forming mechanism and without raising a product cost. SOLUTION: With bellows part 2, an axis A is tilted from the die opening direction X. The mountain-shaped sectional shapes in opposite sides of the axis A of the bellows part 2 are symmetrical with respect to a center 0 to form scalene triangles. Ridge lines 2a, 2b of the chevron shaped part are set to be parallel to the die opening direction X to reduce the amount of undercut at the time of opening the die of the bellows part 2, and to relax resistance to deformation of the bellows part 2 at the time of forcedly drawing out the bellows part. Thus, when the synthetic resin pipe is separated from a forming die M, the vertexes 2d of the bellows part 2 are hard to be caught by the forming plane of the die M, and thus the deformation of the vertexes 2d is eliminated. The synthetic resin pipe can thus be smoothly separated from the die M without damaging the bellows part 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin tube having a bellows at least in a part thereof, and more particularly, to an axis of a cavity in which a bellows of a synthetic resin tube is formed, in which the axis of the cavity is formed in a mold opening direction. The present invention relates to a synthetic resin pipe formed by blow molding or the like in a state where the pipe is inclined with respect to.

[0002]

2. Description of the Related Art A method for blow molding a long tube made of a synthetic resin such as a duct is disclosed in Japanese Patent Application Laid-Open No. 4-74682. In most parts of the duct formed by the method of the publication, the axis is inclined with respect to the mold opening direction of the mold, and a part of the inclined part has a bellows part 5 as shown in FIG.
Are formed. The bellows portion 5 has an isosceles triangular cross section in the axial direction, and the protrusion direction of the mountain is orthogonal to the axis A of the bellows portion 5.

In order to form the duct, the parison is extruded from a molding machine head into a mold, and the parison is inserted along a cavity while being sucked by a blower. Thereafter, the upper and lower shutters are closed, the upper and lower ends of the parison are sandwiched, and the mold is completely closed. Then, compressed air is blown from a blowing pin inserted into the parison to blow-mold the duct. After the molding is completed, the mold is opened to release the duct from the mold.

Usually, a blow molding die is divided into right and left along the axis of a molded product, and the die is opened in a horizontal direction. The above-mentioned duct is also divided into right and left along the inclined axis, and the mold is opened in the horizontal direction. However, the duct is often formed with a bellows portion at an inclined portion thereof, and the bellows portion has a peak projecting direction orthogonal to the inclined axis line, as described above, so that the duct has a And has an inclination angle. Therefore, when the duct is released from the molding die, the peak of the peak of the bellows is undercut and is caught on the molding surface of the mold, and the peak of the peak is forcibly deformed by forcibly deforming the peak of the peak. Will be pulled out.

[0005]

At this time, when an elastomeric resin material having a large amount of rubber components is used for the duct, the undercut portion is easily elastically deformed, so that the undercut portion is relatively easily removed from the molding die. Since it can be pulled out and further restored to its original shape, there is no loss of product value. However, when the duct is made of a resin material having a small elastic deformation performance, it is difficult to elastically deform, so that it is difficult to remove the bellows portion from the mold, thereby lowering the working efficiency and temporarily deforming the molded product. If added, it will be difficult to restore the original shape, and the product value will be impaired. Further, when the duct is formed of a hard resin, the deformation caused by the forcible withdrawal described above causes the peak of the bellows to be lost, resulting in a loss of product value.

For this reason, the mold at the bellows portion is constituted by an independent slide piece that is separate from the molding mold at the other portion.
At the time of opening the mold, a method of sliding the slide piece in a direction orthogonal to the axis of the bellows portion to smoothly release the bellows portion may be adopted. However, in the method using the slide piece, the cost of the mold is increased, so that the product cost is increased. Further, since the independent operation of the slide piece itself is a cause of trouble, the work efficiency is increased. Is significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can release a mold smoothly and efficiently without damaging a bellows portion, without requiring a complicated forming mechanism and without increasing product cost. An object of the present invention is to provide a synthetic resin tube having a bellows structure that can be molded.

[0008]

In order to achieve the above object, the present invention provides a synthetic resin molded tube having a bellows portion having an axis inclined with respect to a mold opening direction of a mold,
The projecting direction of the peak of the bellows portion is inclined from the direction perpendicular to the axis to the mold opening direction to reduce the amount of undercut when the mold is opened and to reduce the deformation resistance of the bellows portion when forcibly pulling out. The main configuration is a synthetic resin tube provided with a bellows portion characterized by relaxing. It is preferable that the synthetic resin tube is integrally formed with a single parison by blow molding.

Although the axis of the bellows portion of the synthetic resin tube is inclined with respect to the mold opening direction, the amount of undercut at the time of opening the mold is reduced and the deformation resistance of the bellows portion at the time of forcible withdrawal is reduced. Due to the shape, when the duct is released from the mold, the bellows is less likely to be caught on the molding surface of the mold, and the bellows is less deformed. Therefore, when the resin tube is made of a synthetic resin material having elastic deformation performance, the bellows portion is not lost or its shape is not deformed to an irreversible shape, and the product value is not impaired. . In addition, since the bellows portion has a shape that reduces the deformation resistance, the bellows portion can be relatively smoothly detached from the mold, thereby improving the working efficiency and suppressing the wear of the mold. In addition, the present invention merely requires the bellows forming mold to have a shape that reduces undercuts when the mold is opened, and does not require a special forming mechanism or equipment. Products can be supplied at low cost.

Further, the present invention is a synthetic resin molded tube having a bellows portion having an axis inclined with respect to a mold opening direction of a molding die, wherein the bellows portion is set so as not to be undercut when the mold is opened. Another main configuration is a synthetic resin tube having a bellows portion characterized by the following. It is preferable that the synthetic resin tube is also integrally formed with a single parison by blow molding.

The bellows of the synthetic resin pipe has an axis inclined with respect to the mold opening direction, but has a shape that does not cause undercut when the mold is opened. The apex of the peak of the bellows is completely prevented from being caught on the molding surface of the mold. Therefore, it is not necessary to deform the bellows portion and forcibly pull out the bellows portion, and the bellows portion can be released as it is, and even when the resin tube is formed of hard resin, the bellows portion is deformed or damaged. It is possible to smoothly pull out the mold without receiving any damage such as the above, and the working efficiency is remarkably improved, and the wear of the mold can be suppressed. Further, since the molding die of the bellows portion is merely shaped so as not to be undercut when the mold is opened, and no special molding mechanism or equipment is required, the production cost does not increase, and the product does not increase. Can be supplied at low cost.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a duct 1 according to a first embodiment of the present invention.
1 is a sectional view of a molding die M of FIG. The duct 1 according to this embodiment is formed of a synthetic resin material having elastic deformation performance, such as an olefin elastomer or LDPE (low density polyethylene). The form is substantially bent in the vicinity of the lower end, and its axis A is inclined at any position with respect to the mold opening direction X of the mold. The mold M of the duct 1 is divided into a right mold RM and a left mold LM along the axis A, and the mold M is opened in the mold opening direction X.
Move to the mold.

The duct 1 has a bellows portion 2 at the center. FIG. 2 shows a sectional view of a molding die of the bellows portion 2.
Also in the bellows part 2, the axis A of the part 2 is inclined with respect to the mold opening direction X. The cross-sectional shape of the mountain that sandwiches the axis A of the bellows portion 2 is symmetrical on the left and right with respect to the axis center O, and each forms a trapezoid triangle. The upper ridge 2a of the chevron formed by the right mold RM and the lower ridge 2b of the chevron formed by the left mold LM are set so as to be parallel to the mold opening direction X. Have been. On the other hand, a valley line B connecting the valley 2c of the bellows portion 2 is orthogonal to the axis A, and a straight line C connecting the left and right vertices 2d is slightly inclined from the orthogonal direction to the axis A of the bellows portion 2.

To form the duct 1, a parison (not shown) is first pushed out of the head of a blow molding machine into a mold M, and the parison is sucked by a blower (not shown) in the same manner as in ordinary blow molding. Insert along. Thereafter, the upper and lower shutters (not shown) are closed to hold the upper and lower ends of the parison, and the mold M is completely closed.
Compressed air is blown from a blow pin (not shown) inserted inside the parison to form the duct 1. After the molding is completed, the mold M is opened right and left along the axis A in the mold opening direction X to release the duct 1 from the mold M.

When the mold is opened, the bellows portion 2 of the duct 1 has its ridge lines 2a and 2b of the chevron portion parallel to the mold opening direction X, eliminating the undercut amount at each vertex 2d, and releasing the mold. Since the bellows 2 has a shape that reduces the deformation resistance, the peak 2d of the peak does not get caught on the molding surface of the ridges 2a and 2b in the mold M, and there is no deformation of the peak 2d. However, a small amount of frictional resistance is generated at the valley 2c when the mold is released. Therefore, the shape of the bellows portion 2 may be slightly deformed. However, when the molding material is a synthetic resin material having elastic deformation performance such as an olefin-based elastomer or LDPE (low-density polyethylene), It is easy to restore to the original shape, the desired product form is secured,
There is no loss in product value. Further, since the bellows portion 2 is relatively smoothly separated from the mold M, the working efficiency is not reduced.

FIG. 3 is a sectional view of a mold for forming the bellows 2 'according to a modification of the first embodiment. Also in this modification, the axis A of the bellows portion 2 'is inclined with respect to the mold opening direction X. The bellows portion 2 ′ has an upper ridge line 2 a ′ in a portion formed by the right mold RM and a lower ridge line 2 a ′ in a portion formed by the left mold LM, similarly to the bellows portion 2 of the first embodiment described above. Is formed in such a shape that the ridge line 2b 'is parallel to the mold opening direction X. However, the valley 2 of the bellows 2 '
c 'is formed deeper than the valley 2c of the bellows portion 2 described above. Therefore, the straight line C 'connecting the left and right vertices 2d' of the bellows portion 2 'is directed more toward the mold opening direction X than in the case of the first embodiment described above, from a direction perpendicular to the axis A of the bellows portion 2'. More inclined. Since the bellows portions 2 ″ at both ends along the axis A are continuously formed with the same diameter as the outer diameter of the duct main body 1 ′, the valley 2 of the central bellows portion 2 ′ is formed.
The diameter is larger than the diameter of c ', and the mountain shapes on the left and right sides are asymmetric with respect to the axis center O'.

Due to the bellows configuration, the bellows portion 2 ′ according to the present modification has a smaller number of undercuts in the valleys 2 c ′ than the above-described bellows portion 2. The deformation resistance of the bellows 2 'is reduced. Accordingly, the form stability of the bellows portion 2 'when the mold is opened is further improved, the releasability is improved, and the work efficiency is further improved.

FIG. 4 is a sectional view of a mold for forming the bellows portion 4 of the duct 3 according to the second embodiment of the present invention. The duct 3 is blow-molded from a hard synthetic resin such as PP (polypropylene) or PE (polyethylene).
Also in the bellows part 4, the axis A of the part 4 is inclined with respect to the mold opening direction X. The cross-sectional shape of the mountain shape sandwiching the axis A of the bellows portion 4 is symmetrical on the left and right with respect to the axial center O ″, and each forms a trapezoidal triangle. The bellows portion 4 is connected to a valley line D connecting the valley 4c. Both the mountain lines E connecting the vertices 4d of the right and left mountains are parallel to the mold opening direction X.

The bellows portion 4 according to the present embodiment is blow-molded in the same manner as in ordinary blow molding according to the above-described procedure, and then the mold is opened and released from the same mold. At this time,
As described above, the bellows portion 4 has the apex 4 of the left and right ridges, although the axis A is inclined with respect to the mold opening direction X.
d is parallel to the mold opening direction X, so that the vertex 4d of the peak of the bellows portion 4 is the ridge line 4a, 4b in the mold M.
It is completely prevented from being caught on the molding surface of the portion, and there is no deformation of the vertex 2d. Furthermore, since the valley line D is also made parallel to the mold opening direction X, there is no undercut portion in the valley 4c at the time of mold release. Therefore, when the bellows part 4 is released from the mold M, no part of the bellows part 4 is caught on the molding surface of the mold M. Therefore, the bellows portion 4 is smoothly pulled out from the mold M in the same form without being deformed, and even if the duct 3 is made of a hard resin as in this embodiment, the bellows portion 4 is damaged. There is no loss of product value. Further, since no frictional resistance is generated between the mold M and the duct M, the duct 3 can be pulled out from the mold M very smoothly, and the working efficiency is remarkably improved, and the wear of the mold can be suppressed.

[0020]

As described above, even when the bellows portion of the synthetic resin pipe has its axis inclined with respect to the mold opening direction, the bellows portion reduces the amount of undercut when the mold is opened. Since the shape of the bellows part is relaxed when forcibly withdrawn, the bellows part is less likely to be caught on the molding surface of the mold when the bellows part is released from the molding die, and the deformation is reduced. Become. Therefore, when the resin tube is made of a synthetic resin material having elastic deformation performance, the bellows portion is not damaged or its shape is not deformed to an irreversible shape, and the product value may be impaired. Absent. Further, since the bellows portion has a shape to reduce its deformation resistance, the bellows portion is relatively smoothly separated from the mold,
Work efficiency can be improved, and wear of the mold can be suppressed. In addition, the present invention merely requires the bellows forming mold to have a shape that reduces undercuts when the mold is opened, and does not require a special forming mechanism or equipment. Products can be supplied at low cost.

Further, when the bellows portion is set so as not to be undercut when the mold is opened, it is possible to completely prevent the bellows portion from being caught by the mold when the duct is released from the mold. Can be avoided. Therefore, the bellows portion is smoothly released in its original form without being deformed at all, and in particular, when the resin tube is formed of a hard resin, the bellows portion is not damaged or deformed or damaged. Not only high quality is guaranteed, but also the work efficiency is remarkably improved and the wear of the mold can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold for forming a duct according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a molding die for a bellows portion.

FIG. 3 is a sectional view of a bellows forming die according to a modification of the first embodiment.

FIG. 4 is a sectional view of a mold for forming a bellows portion in a duct according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a conventional bellows forming die.

[Explanation of symbols]

 1 Duct 2, 2 ', 2 "bellows 2a, 2a' ridge 2b, 2b 'ridge 2c, 2c' valley 2d, 2d 'peak of mountain 3 duct 4 bellows 4a ridge 4b ridge 4c valley 4d peak of mountain 5 bellow Part A Axis B Valley line C, C 'Straight line D Valley line E Mountain line X Mold opening direction O, O', O "Shaft center RM Right mold LM Left mold

Claims (4)

[Claims] 1. A synthetic resin molded tube having a bellows portion having an axis inclined with respect to a mold opening direction of a molding die,
The projecting direction of the peak of the bellows portion is inclined from the direction perpendicular to the axis to the mold opening direction to reduce the amount of undercut when the mold is opened and to reduce the deformation resistance of the bellows portion when forcibly pulling out. A synthetic resin tube provided with a bellows portion, characterized in that the pressure is reduced. 2. The synthetic resin tube according to claim 1, wherein the synthetic resin tube is formed integrally with a single parison by blow molding. 3. A molded pipe made of synthetic resin having a bellows portion having an axis inclined with respect to a mold opening direction of a molding die,
A synthetic resin tube having a bellows portion, wherein the bellows portion is set to a shape that does not cause undercut when the mold is opened. 4. The synthetic resin tube according to claim 3, wherein the synthetic resin tube is formed integrally with a single parison by blow molding.