JPH0586741B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a corrugated pipe with a sleeve, particularly a sleeve equipped with a protrusion that is engaged with the peak of another corrugated pipe connected via the sleeve. The present invention relates to a method for manufacturing a corrugated pipe with a sleeve.

[Conventional technology]

A synthetic resin corrugated pipe having an outer wall with alternating peaks and valleys has a high earth pressure resistance strength because the peaks and valleys act as reinforcing ribs to prevent the corrugated pipe from deforming. Because it is relatively lightweight and flexible, it is often used for agricultural and civil engineering culvert drainage pipes. Such corrugated pipes are often connected using sockets, but from the viewpoint of workability, it is recommended to integrally equip the end of the corrugated pipe with a sleeve as a socket, and connect another corrugated pipe to this sleeve. It is better to connect by inserting the end of the For this reason, in recent years, corrugated pipes with sleeves, in which sleeves are integrally extended to the ends of the corrugated pipes, have come into use.

Conventional sleeved corrugated tubes are made by heat-sealing a sleeve with an outwardly expanding tapered inner peripheral surface and the end of the corrugated tube. It has been pointed out that the corrugated pipes tend to come loose and come loose easily at the connections between the corrugated pipes.

Therefore, a corrugated pipe with a sleeve was proposed in which the sleeve was provided with a protrusion projecting inwardly. According to such a corrugated tube with a sleeve, the crest of the corrugated tube inserted into the sleeve engages with the protrusion and prevents the corrugated tube from coming out of the sleeve, thereby preventing loosening of the connecting portion between the corrugated tubes. and detachment is prevented.

Conventionally, this type of sleeved corrugated tube is produced by injecting molten resin into the sleeve molding space between an outer mold with a protrusion molding surface and a core (hereinafter referred to as the core) with a protrusion molding surface. After injection molding the sleeve and the protrusion at the same time, the outer mold is opened and the core is extracted while expanding the molded sleeve against its elasticity.

[Problem that the invention seeks to solve]

In such conventional methods, if the protrusions are made too high, the protrusions become clumsy and it becomes impossible to extract the core.

However, if the height of the protrusion is set to such an extent that the core can be pulled out of the molded sleeve, during actual use, the width of the engagement portion between the peak of the corrugated pipe inserted into the sleeve and the protrusion (hereinafter referred to as Since the engagement width (referred to as the engagement width) cannot be made sufficiently large, the protrusions can easily come off from the ridges when the connecting portions of the corrugated pipes are deformed flat due to external forces such as earth pressure, and the sleeves can easily separate from the protrusions. There were concerns that the connection would come loose or come off as the corrugated pipe came off.

The present invention solves such problems, and aims to provide a method for manufacturing a sleeved corrugated tube that can sufficiently increase the engagement width.

[Means for solving problems]

In order to achieve the above object, the method for manufacturing a sleeved corrugated tube of the present invention includes a cylindrical parison formed by injection molding at the end of a corrugated tube having an outer wall in which peaks and valleys are interconnected alternately. is simultaneously extended integrally during its injection molding, and then the parison is inflated by blow molding, and a sleeve into which the end of another corrugated tube is inserted and a sleeve protruding inwardly of this sleeve are formed. The gist is to form a protrusion that engages with the peak of the corrugated pipe.

[Effect]

According to the above manufacturing method, by raising the protrusion forming surface of the blow molding die, it is possible to easily integrally provide the sleeve with a tall protrusion.

〔Example〕

Figure 1A shows a cylindrical parison 2 at the end of the corrugated tube 1.
The figure shows the case where the two are extended together. In the figure, reference numeral 3 denotes an outer mold, which is composed of a plurality of divided molds. 4 is a core, and when the core 4 is inserted into the outer mold 3, a parison molding space is formed between the outer mold 3 and the core 4.

The corrugated tube 1 is inserted into the outer mold 3 with two to three peaks at its end facing the parison molding space, and the opening at the end is closed by the core 4. From this state, the molten resin is poured into the parison molding space through the molten resin injection hole 5 of the outer mold 3.
For example, molten polyvinyl chloride resin or polyethylene resin is injected to fill the parison molding space with the molten resin. In this way, at the same time as the parison 2 is injection molded, the parison 2 is integrally heat-sealed and extended to the end of the corrugated tube 1. During this injection molding, it is of course optional to heat the end of the corrugated tube 1 to quickly and reliably heat-fuse it with the molten resin. After injection molding the parison 2, open the outer mold 3 and insert the core 4.
After being extracted from the parison 2, the parison 2 is blow-molded to form a sleeve.

Figure 1B shows the above parison 2 in the blow molding mold.
Figure C shows the state in which blow molding is in progress. In these figures, reference numeral 6 denotes an outer mold, which is composed of a plurality of split molds. This outer mold 6 has a sleeve molding surface 7 having a larger diameter than the parison 2,
The sleeve molding surface 7 is provided with annular rib molding surfaces 8, 8 and protrusion molding surfaces 9 at predetermined locations. Reference numeral 10 denotes a core provided with an air outlet (not shown), and a bulge 11 is provided at the distal end of the core to be inserted into the end of the corrugated tube 1 to close the end opening.

As shown in FIG. 1B, the parison 2 is set inside the outer mold 6, and the end opening of the corrugated tube 1 is inserted into the core
After the parison 2 is closed by the bulge 11, air is blown from the core 10 as shown by the arrow in FIG. Align it along surface 9. As a result, the sleeve 12, protrusion 13, and rib 14 are simultaneously blow-molded. After curing, the outer mold 6 is opened and the core 10 is extracted from the sleeve 12. Here, since the protrusion 13 is provided on the sleeve 12 formed by inflating the parison 2, unless the protrusion 13 is extremely tall, the protrusion 13 will be removed when the core 10 is extracted from the sleeve 12. 13 will never be boring. In addition,
When performing the above blow molding, if necessary, the second
Parison 2 set in outer mold 6 as shown in the figure
The tip portion 2a of the parison 2 may be sandwiched between the outer mold 6 and the core 10 to prevent the length of the parison 2 from being shortened when the parison 2 is expanded by blow molding.

The sleeved corrugated pipe manufactured in this way is
As shown in the figure, a sleeve 12 extends integrally to the end of the corrugated tube, and this sleeve 12
It has annular ribs 14 at a plurality of locations, and a plurality of protrusions 13 that protrude inward between these ribs 14.

FIG. 4 shows the state in which the sleeved corrugated pipe is used. As is clear from the figure, sleeve 1
The protrusion 13 engages with the crest 1a' of another corrugated tube 1' inserted into the corrugated tube 2, thereby preventing the corrugated tube 1' from slipping out.

Here, the engagement width between the peak 1a' and the protrusion 13 increases as the height of the protrusion 13 increases, and conversely decreases as the protrusion 13 becomes lower. becomes difficult to slip out of the sleeve 12. On the other hand, if the height of the protrusion 13 is too high, when another corrugated tube 1' is inserted into the sleeve 12, the protrusion 13 will become too tight, making it impossible to insert it. Therefore, the protrusion 13 should be made as high as possible without making it impossible to insert another corrugated tube 1' while expanding the sleeve 12 against its elasticity. desirable. In this respect, since the protrusions 13 are formed at the same time when the parison 2 is blow-molded to form the sleeve 12, even if the protrusions 13 are made as tall as possible within the above range, the core 10 is
The protrusion 13 does not become jammed when pulled out from 2. Therefore, the tall protrusion 13 can be formed without any inconvenience.

In addition, in this embodiment, since the sleeve 12 is reinforced by the ribs 14, even if earth pressure acts in a direction that deforms the sleeve 12 into a flat shape, the sleeve 12
2 deformation is suppressed to a minimum. Therefore, the engagement width between the protrusion 13 and the crest 1a' can be increased, and the connection portion of the corrugated pipes 1, 1' may be deformed and the engagement between the protrusion 13 and the ridge 1a' may be disengaged. This prevents the situation from happening and ensures that the connection parts do not come loose or come off. Further, if the necessary strength is ensured by the ribs 14, the sleeve 12 can be made thinner, so that the yield of the material is improved.

〔Effect of the invention〕

In the manufacturing method of the present invention, since the protrusions are blow-molded at the same time as the sleeve, a sleeve with tall protrusions can be easily formed. Therefore, it becomes possible to easily manufacture a corrugated tube with a sleeve, which has a sleeve that makes it difficult for a corrugated tube once inserted to come out, although it is easy to insert another corrugated tube.

[Brief explanation of the drawing]

FIG. 1A is a cross-sectional view showing a case in which a parison is integrally extended to the end of a corrugated pipe, and FIG. 1B is a cross-sectional view showing a state in which the parison is set in a blow molding mold.
Figure C is a sectional view showing the state during blow molding.
The figure is a partial cross-sectional view showing a modified example of a blow molding mold, FIG. 3 is a partial cross-sectional view showing a sleeved corrugated tube manufactured by the method of the present invention, and FIG. 4 is a partial cross-sectional view showing a sleeved corrugated tube manufactured by the method of the present invention. It is a partial sectional view showing a state. 1...Corrugated tube, 2...Parison, 12...Sleeve, 13...Protrusion.

Claims (1)

[Claims] 1. A cylindrical parison formed by injection molding is integrally extended at the end of a corrugated pipe having an outer wall in which peaks and valleys are connected alternately during injection molding, and then the parison is It is characterized by being inflated by blow molding to form a sleeve into which the end of another corrugated tube is inserted, and a protrusion that protrudes inward of this sleeve and is engaged with the peak of the another corrugated tube. A method of manufacturing a corrugated pipe with a sleeve.