JPH0129351Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is based on a plastic pipe whose tube wall is made of two types of thermoplastic resins: a hard thermoplastic resin and a more flexible thermoplastic resin, and has a corrugated helical cross-section. In pipes, in particular, it gives flexibility to hard plastic pipes, gives them deformation absorption ability, and improves impact fracture resistance due to the low toughness of hard plastic pipes.
Another object of the present invention is to provide a corrugated flexible tube having a high degree of resistance to external pressure and strength.

Corrugated flexible tubes made of thermoplastic resin have characteristics such as corrosion resistance, chemical resistance, and magnetism compared to metals, as well as being lightweight, relatively flexible, and easy to process. For these reasons, metal tubes have recently been replaced in many fields, but the tube walls of these corrugated flexible tubes were basically composed of a single thermoplastic resin.

Therefore, if you want to further improve flexibility,
Is the entire component made of soft thermoplastic resin?
Alternatively, there is no choice but to reduce the wall thickness of the tube wall, and as a result, the tube's internal pressure resistance and external pressure resistance naturally decrease.

Conversely, to improve the strength characteristics of the tube,
Since hard thermoplastic resin is used as the tube material or measures are taken to increase the thickness of the tube wall, the flexibility of the tube is lost, and especially when the tube wall is thickened, the weight increases. This not only increases the amount of energy used, but also increases costs.

There are also rubber bellows hoses that have hard plastic wires embedded in them, but these cannot be expected to have great resistance to external pressure.

Therefore, as a result of searching for a new corrugated flexible tube that has high external pressure resistance and flexibility, the inventors found that 1 of the tube wall height H from the inner wall surface to the outer wall surface of the tube. It has a continuous wave-shaped pipe wall with a wave-shaped cross section, in which an outer part 2 whose axial cross-section has a substantially inverted U-shape and an inner part 2 which has a substantially U-shape continue alternately, bordering on /2, This is a plastic tube in which the tube wall is integrally formed of a hard thermoplastic resin and a more flexible thermoplastic resin, and the more flexible thermoplastic resin covers the entire inner part or at least the inner wall surface of the tube. By using a corrugated flexible tube with a structure in which the bottom part is located within a height range equivalent to the thickness of the tube wall from It has been discovered that a suitable hard corrugated flexible tube that cannot be obtained with conventional structures can be obtained.

In other words, the outer part bordering on 1/2 of the pipe wall height H has an inverted U-shaped cross section from the outside inward, which is a shape that has high deformation resistance and support against external pressure. The entire part and even the bottom part of the inner part are made of hard thermoplastic resin, giving it great resistance to external pressure, and at least the bottom part of the inner part is made of highly flexible thermoplastic resin. In particular, suitable flexibility is ensured.

When molding, the outer part and the middle part may be integrally molded using resins of different properties depending on the plastic extrusion molding machine.

Next, aspects of this invention will be specifically explained based on illustrative drawings.

FIG. 1 is a partial sectional view in the axial direction showing one embodiment of the corrugated flexible tube according to the invention, FIG. 4 is a partial sectional view of another embodiment with a different waveform, and FIGS. FIG. 3 is an enlarged sectional view showing how hard and soft thermoplastic resins are used in the tube wall.

In the figure, SW is the spiral waveform of the flexible tube, and TP is the trough. 1 is the outer part whose axial cross section is almost inverted U-shaped, and 2 is the inner part which is almost U-shaped, with a series of alternating cross-sectional wave shapes with 1/2 of the pipe wall height H as the boundary. It has a corrugated tube wall.

The state of selective use of hard and soft thermoplastic resins shown in FIG.
This shows an example in which the area indicated by a, that is, the entire inner part is made of a highly flexible thermoplastic resin.

In addition, the state in which hard and soft thermoplastic resins are selectively used as shown in FIG. The remaining portion 1b, which includes the entire outer portion 1 and the inner portion 2, is made of a highly flexible thermoplastic resin.
An example is shown in which the portion up to the vicinity of the bottom portion 2b is made of hard thermoplastic resin.

In this example, the portion including the bottom portion 2b and slightly toward the outer side is formed of a highly flexible thermoplastic resin, but at least the bottom portion 2b may be formed of a thermoplastic resin.

Fig. 4 shows an example in which at least the bottom part 2b is made of thermoplastic resin, together with a modified example of the waveform. Only the bottom part 2b where the position is located is made of highly flexible thermoplastic resin, and the outer part 1
The tube wall of the remaining portion 1b including the entire tube is made of hard thermoplastic resin. Of course, in this example as well, a highly flexible thermoplastic resin may be used for the entire inner part 2.

As mentioned above, the entire outer part of the tube wall protruding outward or its extension is made of hard thermoplastic resin, so it has excellent linear shape retention and deformation against external pressure like metal. On the other hand, at least the bottom of the inner part is made of highly flexible thermoplastic resin, so it is a rigid tube with high resistance to external pressure and strength. It has the characteristics of providing flexibility and preventing impact fracture due to the low toughness of hard plastic tubes.

In addition, even when buried in the ground, it not only withstands large lateral pressures and adapts to ground fluctuations, but also exhibits the ability to absorb deformation and prevents damage due to the low toughness of hard resin. It exhibits excellent durability. Therefore, since an increase in the thickness of the tube wall can be suppressed, the tube can be made lightweight. Furthermore, since different types of thermoplastic resins form an integral structure through strong intermolecular fusion bonding, it has the advantage that a good-quality, hard, corrugated flexible tube can be obtained extremely easily through a single extrusion process. There is.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view in the axial direction showing an embodiment of the hard corrugated flexible tube according to this invention, and FIGS. 2 and 3 are enlarged views showing the different uses of thermoplastic resin in the tube wall. The sectional view, FIG. 4, is a partial sectional view showing another embodiment of the corrugated flexible tube. 1...outer part, 2...inner part, 1a, 1b...
Range of hard thermoplastic resin, 2a, 2b... Range of highly flexible thermoplastic resin.

Claims (1)

[Scope of utility model registration request] 1/2 of the pipe wall height H from the inner wall surface to the outer wall surface of the pipe
It has a continuous wave-shaped pipe wall with a wave-shaped cross section, in which an outer part 1 whose axial cross section is approximately inverted U-shaped and an inner part 2 which is approximately U-shaped are alternately continuous, with
This is a plastic tube whose tube wall is integrally formed of a hard thermoplastic resin and a more flexible thermoplastic resin. Bottom portion 2b located within a height range equivalent to the thickness of the tube wall from the wall surface
A rigid corrugated flexible tube used in the construction of a rigid, corrugated flexible tube in which at least the remainder of the tube wall, including the entire outer section, is made of a rigid thermoplastic resin.