JPS6334011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a double pipe made of synthetic resin used for civil engineering drainage pipes, etc., more specifically, a so-called corrugated pipe in which large diameter parts and small diameter parts are repeated alternately is used as an outer cylinder. The present invention relates to an effective continuous manufacturing method for a double pipe in which a small diameter portion and a straight inner cylinder are fused and integrated.

Synthetic resin corrugated pipes have been widely used as drainage pipes for civil engineering. Even though the corrugated pipe is relatively thin, the pipe wall has regular irregularities along the axial direction, so it has much higher buckling resistance than general straight synthetic resin pipes, and Since it is a molded body of synthetic resin, there is no risk of rusting, and it is easy to mold, and in addition, it is lightweight and inexpensive, so it is extremely suitable as the above-mentioned civil engineering drainage pipe buried in the soil. As described above, the above-mentioned corrugated pipe has various advantages, but in terms of drainage efficiency, since the inner surface, which serves as a fluid flow path, has an uneven surface, the flow resistance is large and solid matter in the fluid tends to accumulate. It contained the drawbacks of. Therefore, recently, in order to eliminate such drawbacks, the inner surface is lined with a synthetic resin sheet, or by co-extrusion with a synthetic resin straight pipe, the outer cylinder of a corrugated pipe and the inner cylinder of a straight pipe are made. Measures such as installing double pipes have begun to be taken. To manufacture the latter double pipe, an extrusion nozzle equipped with an internal and external dual annular synthetic resin extrusion passage is introduced into the continuous molding equipment for ordinary corrugated pipes made into mold blocks, and the outer cylinder is A continuous molding method (for example, a method using an apparatus disclosed in Japanese Patent Publication No. 46-9673) is employed in which unevenness is provided and the inner cylinder is made into a straight pipe and these are fused and integrated. In this method, a double heat-softened synthetic resin tube (outside and outside) extruded from an extrusion nozzle is expanded by air pressure injected into the inside.
Manufacturing of the above-mentioned double pipe, in which the outer cylinder is brought to the inner circumferential wall of the molded frame block, unevenness is imparted thereto, and the inner cylinder is integrally fused to the outer cylinder in a straight pipe state. However, since both the inner and outer cylinders are expanded by air pressure, if the balance of air pressure between the two is disrupted, the inner cylinder will lack smoothness or it will be difficult to achieve fusion between the two, and furthermore, the pressurized air will cause rapid cooling. Therefore, depending on the resin, there still remained technical problems to be solved, such as cracks occurring when strain occurs due to the difference in shrinkage between the inner and outer cylinders.

In view of the above, the present invention has been made by further improving the prior art described above, and is a novel manufacturing method for synthetic resin double pipes that can efficiently and stably supply high-quality products. The purpose is to provide

Embodiments of the present invention will be explained based on the accompanying drawings. Fig. 1 is a vertical cross-sectional view of a main part showing an example of a device in which the method of the present invention is adopted, and Fig. 2 is a cross-sectional view of a double pipe obtained by the method of the present invention. FIG. 3 is a partially cutaway front view. That is,
The present invention consists of two series of molded frame blocks 1, each of which is endlessly connected to each other. block assembly 10,
10 are partially engaged with each other in a facing relationship and run under cooperative regulation to form a tunnel-shaped molding zone 2, and from the rear end of the molding zone 2, a double inner and outer annular passage for extruding synthetic resin is formed. By inserting the thermoplastic synthetic resin extrusion nozzle 3 coaxially containing the passages 31 and 32, and continuously extruding the thermo-softened inner and outer dual synthetic resin pipes P ₀₁ and P ₀₂ from the passages 31 and 32. , the outer cylinder P ₁ is given irregularities in which the large diameter part P ₁₁ ... and the small diameter part P ₁₂ ... are repeated alternately, and the inner cylinder P ₂ is made straight, and the small diameter part P ₁₂ ... of the outer cylinder P ₁ is made straight. In the continuous manufacturing method of the synthetic resin double pipe P which is integrally fused, the molding process in the molding zone 2 into which the extrusion nozzle 3 is inserted includes heat softening in the first region 21 behind the extrusion nozzle 3. The synthetic resin pipe P ₀₁ for the outer cylinder in the state is extruded and expanded in the centrifugal direction by air pressure injected from the air supply passage 33 installed inside the nozzle 3 to reach the uneven inner peripheral wall of the molding frame block 1. In the first step, the pressurized air transferred as the molding frame blocks 1 are moved is unified in a second region 22 which is located in front of the region 21 and is substantially cut off from the region 21. a second step of extruding the thermally softened synthetic resin pipe P ₀₂ for the inner cylinder along the outer periphery of the front end 30 of the nozzle 3 and fusing it to the small diameter part of the synthetic resin pipe P ₀₁ for the outer cylinder; Superheated steam is introduced from outside the system through the extrusion nozzle 3 into the third region 23 defined by the heat insulating member 4 attached to the front end of the nozzle 3 and the stopper 5 disposed in front of it. A method for producing a synthetic resin double pipe, comprising a third step of spray filling and slowly cooling the mutually fused double synthetic resin pipes P ₀₁ and P ₀₂ from the inside. be. In FIG. 1, the extrusion nozzle 3 includes two types of extrusion dies 301 and 302 for extruding the synthetic resin pipes P ₀₁ and P ₀₂ for the inner and outer cylinders. The synthetic resins R ₁ and R ₂ are formed in double annular passages 31 and 3 installed inside the nozzle 3 body, respectively.
2 and then extruded from the dies 301 and 302. These two types of extrusion dies 301 and 302 are arranged in front and behind to extrude the synthetic resin pipes P ₀₁ and P ₀₂ for the outer cylinder and the inner cylinder, respectively, and the extrusion die 302 for the inner cylinder in the front
Further, the outer mold 302′ and the inner mold 3 located in the front and rear
02''. This outer mold 30
2' has an outer diameter approximately equal to the small diameter portion of the synthetic resin pipe P ₀₁ extruded and molded by the outer cylinder die 301, thereby forming the first region 21 and the second region 22. will be virtually blocked. In addition, the inner mold 302'' projects forward from the outer mold 302' in an enlarged diameter shape, and is formed such that its outer diameter at its tip is approximately equal to the inner diameter of the inner cylinder _P2 of the double pipe P. The extrusion nozzle 3 further includes a compressed air supply passage 33 for expanding the synthetic resin pipe P ₀₁ for the outer cylinder in the first region 21, and a part of the compressed air in the second region 22. An exhaust passage 34 for controlling release to the outside of the system and a conduit 35 for injecting and filling the third region 23 with superheated steam are provided, and the conduit 3
A stopper 5 is connected and fixed to the tip of the stopper 5. also,
The front end of the extrusion nozzle 3, that is, the extrusion die 302 for the inner cylinder
A heat insulating member 4 is attached to the tip of the insulating member 4, which is a hollow molded body made of synthetic resin such as Teflon, and as described later, the die 302 and the third region 23 maintain an optimum temperature. It is designed to block heat from entering and exiting both sides. still,
In the figure, another heat insulating member 51 is interposed between the die 302 and the conduit 35, but this is also provided to suppress the cooling of the die 302 by the superheated steam passing through the conduit 35 for the same purpose as above. It is.

A forming frame block 1..., two block assemblies 10, 10 connected endlessly, and these block assemblies 10, 10 are partially opposed to each other and engaged with each other, and run under cooperation regulation. The system consisting of the molding zone 2 thus formed is similar to the mold block equipment employed for the production of conventional corrugated pipes, and is shown in the figure by arrow a.
It is shown that the assemblies 10, 10 are traveling in the direction and the extrusion nozzle 3 is inserted into the molding zone 2 from the rear.

To explain in more detail the method for manufacturing the double pipe P using the above-mentioned device, the block assembly 1 traveling in the direction of the arrow a.
The extrusion nozzle 3 is inserted into the molding zone 2 formed by the die 30 in the first region 21.
Extrude the synthetic resin pipe P ₀₁ for the outer cylinder from 1 and connect it to the air supply passage 3.
The air pressure injected from 3 expands this in the centrifugal direction and reaches the uneven inner circumferential wall of the molding frame block 1 to give it unevenness (first step).
The synthetic resin pipe P ₀₁ molded as the assemblies 10 and 10 travel is inserted into the outer mold 3 of the inner cylinder extrusion die 302.
It moves to the second area 22 while slidingly contacting the outer periphery of 02'. At this time, the air pressure injected in the first region 21 is maintained in the recess in the synthetic resin pipe P ₀₁ and transferred to the recess in the synthetic resin pipe P 01. The pressure inside the region 22 becomes approximately equal to atmospheric pressure after being released outside the system.
In this second region, the inner cylinder synthetic resin pipe P ₀₂ is extruded from the inner cylinder die 302 along the outer circumference of the inner mold 302'', and the front end 30 of the extrusion nozzle 3, that is, the tip of the inner mold 302'' In the above synthetic resin pipe for the outer cylinder
P ₀₁ and is fused to this small diameter part (second
process). Double synthetic resin pipes fused together
P ₀₁ and P ₀₂ further move to the third region 23, where they are slowly cooled from the inside by superheated steam injected from small holes 351 bored in the conduit 35. This superheated steam is steam at a temperature of 100 to 110°C and has a steam pressure slightly above atmospheric pressure, and the third region 23 is filled with the excess steam, which is combined with the plug body 5 disposed in front. It is released outside the system through the clearance with the resin pipe P ₀₂ . When introducing the superheated steam, it is important not only to maintain its temperature but also to maintain a pressure that will not cause dents or sag in the soft synthetic resin pipe P ₀₂ within the third region 23. Although not shown, it goes without saying that the conduit 35 should be appropriately equipped with a pressure regulating valve or the like outside the system (third step). A double synthetic resin tube slowly cooled in this way
P ₀₁ and P ₀₂ are continuously discharged out of the device through the stopper 5, and after being cooled and solidified, an outer cylinder is formed in which large diameter portions P ₁₁ and small diameter portions P ₁₂ are alternately repeated as shown in Fig. 2. P ₁ and the straight inner cylinder P ₂ are fused together to form a synthetic resin double pipe P.

In the above manufacturing process, the synthetic resin pipe P ₀₂ for the inner cylinder is extruded along the outer periphery of the inner mold 302'' and is fused as it is to the small diameter part of the synthetic resin pipe P ₀₁ for the outer cylinder. Unlike the method of pressurizing air from inside to inflate and fuse, there is no concern that the pipe wall of the synthetic resin pipe P ₀₂ for the inner cylinder will lack smoothness, and it can be literally fused to the outer cylinder as a straight inner cylinder. Moreover, since these are in a semi-solidified state when moving to the third region 23, there is little risk that the synthetic resin pipe P ₀₂ for the inner cylinder will dent or sag. This concern is eliminated by the action of the superheated steam whose pressure is regulated as described above, and the pipe is cooled while maintaining its smoothness and straightness, and the double pipe P with a uniform shape as shown in Fig. 2 is efficiently manufactured. In the third region 23, the superheated steam gradually cools the tube so as to ripen it from the inside, so the inner and outer tubes are cooled evenly, and there is no risk of distortion due to the difference in shrinkage. This effect is remarkable when extruded vinyl chloride resin, which is prone to cracking due to strain, is used as the extruded material.The synthetic resin pipe P thus obtained has the same strong buckling strength as conventional corrugated pipes. outer cylinder with
P ₁ and the inner cylinder P ₂ that ensures smooth flow are integrated, and together with its low cost and lightweight characteristics, it is extremely suitable for use as a drainage pipe buried underground. Become. In addition, it is natural that it can be applied not only to such drainage pipes but also to other piping materials, and especially for applications that require heat retention, there is a material between the outer cylinder P ₁ and the inner cylinder P ₂ . In addition to the above-mentioned characteristics, the double-walled pipe P having voids is expected to have new effects.

As described above, according to the method of the present invention, synthetic resin double pipes with a uniform shape and consistent quality can be efficiently manufactured, and the commercial value of the double pipes obtained is high as well as its industrial value. It can be said that its usefulness is extremely high.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a main part showing an example of a device in which the method of the present invention is employed, and FIG. 2 is a partially cutaway front view of a double pipe obtained by the method of the present invention. (Explanation of symbols) 1... Forming frame block, 10... Block assembly, 11... Large diameter part, 12... Small diameter part, 2
...Molding zone, 21...First region, 22...Second region, 23...Third region, 3...Extrusion nozzle, 30
...front end of nozzle, 31, 32... annular passage for extruding synthetic resin, 33... air supply passage, 4... heat insulating member, 5...
Plug body, P...synthetic resin double pipe, P ₁ ...outer tube, P ₂ ...
Inner tube, P ₁₁ ...Large diameter section, P ₁₂ ...Small diameter section, P ₀₁ ...Synthetic resin tube for outer tube, P ₀₂ ...Synthetic resin tube for inner tube.

Claims (1)

[Claims] 1. A plurality of molded frame blocks connected endlessly, each having an inner circumferential wall with an uneven surface formed by alternating regular large-diameter portions and small-diameter portions along the axial direction.2
A series of block assemblies are partially engaged with each other in a facing relationship and run under controlled cooperation to form a tunnel-shaped molding zone, and from the rear end of the molding zone, extrusion of double inner and outer synthetic resin is carried out. By inserting a thermoplastic synthetic resin extrusion nozzle that coaxially includes an annular passage and continuously extruding a heat-softened double inner and outer synthetic resin tube from the passage, a large diameter part and a small diameter part are formed in the outer cylinder. In a method for continuous production of a synthetic resin double tube, in which the inner tube is provided with alternating unevenness and the inner tube is made straight and is fused and integrated with the small diameter portion of the outer tube, the extrusion nozzle is inserted. The molding process in the molding zone
A heat-softened synthetic resin tube for the outer cylinder is extruded in a first region behind the extrusion nozzle, and is expanded in the centrifugal direction by air pressure injected from the air supply passage installed inside the nozzle, thereby forming the molded frame block. The first step of reaching the uneven inner circumferential wall is a second region that is substantially cut off from the region that was in front of the region,
A portion of the pressurized air transferred as the molding frame block travels is released, and the heat-softened synthetic resin pipe for the inner cylinder is extruded along the outer periphery of the front end of the nozzle, and the small diameter portion of the synthetic resin pipe for the outer cylinder is extruded. The second fused to
and inject superheated steam introduced from outside the system through the extrusion nozzle into a third region defined by a heat insulating member attached to the front end of the nozzle and a stopper disposed in front of the heat insulating member. A method for manufacturing a synthetic resin double pipe, comprising a third step of filling the double synthetic resin pipe and gradually cooling the mutually fused double synthetic resin pipe from the inside.