JPS5831288B2 - Manufacturing equipment for spirally corrugated plastic pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to reduce the gap between the resin pipe and the mandrel when extruding a resin pipe using a so-called mandrel using a polyolefin resin such as polyethylene, polycarbonate resin, or other general thermoplastic resin as a material. The present invention relates to a method for manufacturing a spirally corrugated plastic tube which has beautiful skin on both the inner and outer surfaces and excellent mechanical properties, by molding the resin tube in close contact with a mandrel by applying negative pressure.

Conventionally, various methods for manufacturing spirally corrugated plastic pipes have been developed.

A typical example is a molding method in which a resin pipe is placed in a desired mold, air pressure is applied inside the pipe while heat is applied, and the pipe is pressed against the spirally corrugated inner wall of the mold.

However, this method requires complicated steps, requires labor, and is inefficient.

Furthermore, the length of the tube is regulated by the mold used, and in order to meet various demands, it is necessary to prepare a huge number of molds with different lengths and diameters, which requires a huge amount of money. There are drawbacks such as being able to only do things.

A method using a so-called mandrel has been developed which solves the above-mentioned drawbacks and allows continuous molding of a long object in one piece and requires fewer steps and saves labor.

As shown in Fig. 1, a mandrel 4 having a spirally corrugated outer circumferential surface is attached to the extruder in front of the die 2 of the extruder in the extrusion direction so that the mandrel 4 can rotate in the direction of the outer circumferential surface, and the thermoplastic resin is supplied from the extruder. The resin pipe 6 is heated and melted and extruded onto the outer peripheral surface of the mandrel 4 as a resin pipe 6, and the gap 8 between the resin pipe 6 and the mandrel 4 is formed up to the position where the resin pipe 6 starts to come into contact with the mandrel 4.
is connected to a negative pressure source (not shown) through a pipe 10 to create a negative pressure and suction is applied, the resin pipe 6 is placed along the outer peripheral surface of the mandrel 4, and the mandrel 4 is rotated while being cooled, and its spiral waveform part This is a method in which the resin tube 6 is sent forward one after another.

However, in this method, once the resin tube has made contact with the outer circumferential surface of the mandrel, the suction force due to the negative pressure does not reach the outer circumferential surface of the mandrel. However, since the outer circumferential surface has a spiral waveform and a needle surface, the contraction in the length direction becomes contraction in the direction along the slope, and is regulated by the top of the spiral, so the sides that sandwich the trough As a result of mutual contraction toward the top of the slope, the trough of the resin tube separates from the outer peripheral surface of the mandrel, and as the contraction continues toward the top of the slope, the trough becomes constricted and the inner peripheral surface of the trough Uneven wrinkles may occur, and since the troughs on the inner circumferential surface of the pipe are not in contact with the mandrel, polishing due to friction with the mandrel is not applied, resulting in only the troughs becoming rough.

Therefore, the mechanical properties such as lateral pressure resistance and bending resistance are poor, and there is a risk that the pipe may be deformed or damaged when used under lateral pressure, such as when buried in the ground.

Also, during use, fluid may be difficult to flow, dirt may
Mud and other substances tend to stick to it, which can lead to pipe blockage.

Furthermore, it has disadvantages such as being unsightly and significantly reducing its commercial value.

As a result of various studies to solve the above-mentioned drawbacks, the inventor of the present invention found that after the resin tube contacts the mandrel, the gap between the resin tube and the mandrel is made negative pressure in a certain section until it cools and solidifies to a certain extent, and in that section, the resin tube We have come up with the idea that the above drawbacks can be solved by tightly adhering the material to the mandrel.

That is, the object of the present invention is to provide an apparatus for manufacturing a spirally corrugated plastic tube that has beautiful skin on both the inner and outer surfaces and excellent mechanical properties. Formed into a tapered mandrel that tapers slightly toward the tip, the extruded resin tube begins to come into contact with the mandrel outer circumferential surface and is rapidly cooled. A narrow groove intersecting the spiral of the mandrel and having a circumferential separation angle of 360° or more is provided on the outer circumferential surface of the mandrel, and the narrow groove is connected to an appropriate negative pressure source, and the narrow width in which the narrow groove is provided is A seal portion is provided within the spiral trough on the outer circumferential surface of the mandrel ahead of the area to abut the inner surface of the spiral trough of the extruded resin pipe by making the helical trough of the mandrel shallower.

Embodiments of the present invention will be described below in detail with reference to the drawings. In FIG. 2, 12 is a mouthpiece having an annular slit 14 and fixed to the tip of an extruder 16, 18 is an extruded resin pipe,
20 is a mandrel disposed directly in front of the die 12 facing in the extrusion direction, and 22 is a narrow groove provided on the outer circumferential surface of the mandrel 20.

The mandrel 20 is installed in the crosshead 24 of the extruder 16, and is attached to a drive section (not shown) at the rear of the extruder 16.
It is rotatably connected in the direction of its outer circumferential surface.

The mandrel 20 has a spirally corrugated outer peripheral surface and is slightly tapered.

The purpose of this taper is to facilitate the removal of the resin tube 18.

Although the size of the taper is not particularly limited, it is approximately 4% in this example.

Cooling water is circulated within the mandrel 20, injected through a pipe 26, and drained through a pipe 28.

The narrow grooves 22 are a plurality of loop-shaped narrow grooves, and extend along the circumferential direction of the outer circumferential surface of the mandrel 20 within a certain section from the vicinity where the resin tube 18 starts contacting the outer circumferential surface of the mandrel 20. It is provided to intersect with the spiral of the surface.

The above section is a section from when the resin pipe 18 starts to come into contact with the outer circumferential surface of the mandrel 20 until it cools and solidifies to some extent,
Although it varies depending on the type of resin, the wall thickness and diameter of the tube, and the cooling conditions, the cooling method using normal water cooling
Approximately 0 cm is suitable.

Reference numeral 30 denotes a bridge groove that communicates the loop-shaped narrow grooves 22 with each other. A small hole 32 is bored in the bridge groove 30, and the bridge groove 30 is connected to a vacuum pump (not shown) through a pipe 34.

In another embodiment of the narrow groove 22, the loop-shaped groove 22 may not be provided with the bridge groove 32, but each of the loop-shaped grooves may be provided with a small hole and connected to a vacuum pump.

Further, as shown in FIG. 3, a vacuum pump is used to connect a pipe 38 that communicates with the gap 36 between the resin tube 18 and the mandrel 20 until the extruded resin tube 18 starts to come into contact with the outer peripheral surface of the mandrel 20. (not shown) to create a negative pressure, and the loop-shaped narrow groove 22 and the bridge groove 30 (without small holes) may be communicated with the void 36 through the communication groove 40.

In addition, as shown in FIG. 4, the narrow groove 22 is formed into a coiled narrow groove having a circumferential angle of 360° or more, and the gap shown in FIG. A hole may be bored and the mandrel may be connected to a vacuum pump from inside the mandrel as shown in FIG.

Further, as shown in FIG. 5, a seal portion 42 is provided in the spiral trough near the tip of the mandrel 20 to make the trough slightly shallower.

In order to obtain a spirally corrugated plastic tube with the above configuration, first, cooling water is circulated through the water inlet (not shown) in the mandrel 20, the thermoplastic resin is heated and melted, and the resin tube is formed through the annular slit 14. 18 is extruded onto the outer peripheral surface of the mandrel 20.

The resin tube 18 advances along the outer peripheral surface of the mandrel 20 while being cooled and solidified.

At this time, the gas existing in the gap between the resin tube 18 and the mandrel 20 is discharged through the small holes 32 and the narrow grooves 22, so that the resin tube 18 is moved to the outer peripheral surface of the mandrel 20 within a certain section where the narrow grooves 22 are carved. Proceed in close contact with the top.

In the embodiments shown in FIGS. 3 and 4, negative pressure is also applied to the narrow groove 22.
and performs the same functions as above.

Furthermore, as shown in FIG. 5, by providing the seal portion 42, air is prevented from entering from the tapered tip of the mandrel 20 along the spiral trough, and from the narrow groove 22 into the spiral trough. Negative pressure is applied to the mandrel, and the resin tube is molded in close contact with the outer circumferential surface of the mandrel, at least within the section where the narrow groove 22 is provided.

Then, by rotating the mandrel 20 so that the traveling speed of the spiral wave is synchronized with the extrusion speed of the resin tube 18, the resin tube is screw-fed and sequentially sent forward to produce a spirally corrugated plastic pipe. Ru.

As described above, according to the present invention, since the mandrel is tapered, the pulling resistance of the resin tube is small, and since the mill part is provided to make the trough of the spiral shallower, the trough of the spiral ahead of the groove is Negative pressure is applied to the area, ensuring that the resin tube is in close contact with the outer circumferential surface of the mandrel in the steam width area where the groove exists, resulting in extremely good moldability, and the reliable polishing action of the groove allows the resin to have a beautiful skin. It has the remarkable effect of being able to obtain a tube.

Although the present invention has been variously explained above with reference to preferred embodiments, the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. It is.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional embodiment, FIG. 2a is a sectional view of a preferred embodiment of the present invention, and FIG. 2 is a partial side view of the mandrel. FIG. 3 is a sectional view showing another embodiment of the present invention, FIG. 4 is a schematic view showing a coiled groove of a mandrel, and FIG. 5 is a schematic view showing a seal portion of the mandrel. 2...Mandrel, 4...Mandrel, 6...
... Resin pipe, 8 ... Gap, 10 ...
...Pipe, 12...Base, 14...
Annular slit, 16... Extruder, 18...
Resin pipe, 20... Mandrel, 22...
Thin groove, 24...Cross head, 26, 28...
...Pipe, 30...Bridge groove, 32.
...Small hole, 34...Pipe, 36...
...Gap, 38...Pipe, 40...
・Communication groove, 42... Seal part.

Claims (1)

[Scope of Claims] 1. A mandrel having a spirally wave-shaped outer peripheral surface is provided in front of the extruder mouthpiece in the direction of resin extrusion so as to be rotatable in the direction of the outer peripheral surface, the mandrel is cooled, and semi-molten material is released from the extruder mouthpiece. In the apparatus for manufacturing a spirally corrugated plastic tube, the resin tube is extruded onto the outer circumferential surface of a mandrel, the resin tube is made to follow the outer circumferential surface of the mandrel, and the mandrel is rotated to sequentially feed screws to form the plastic tube. The extruded resin tube is formed into a tapered mandrel that tapers slightly toward the outer circumferential surface of the mandrel, and the extruded resin tube begins to come into contact with the outer circumferential surface of the mandrel and is cooled to a yarn speed. A narrow groove intersecting the spiral of the mandrel and having a circumferential angle of 360° or more is provided on the outer circumferential surface of the mandrel, and the narrow groove is connected to an appropriate negative pressure source to reduce the width of the narrow groove. A helical corrugated plastic tube comprising a helical trough on the outer circumferential surface of the mandrel ahead of the area and a sealing part that contacts the inner surface of the helical trough of the extruded resin tube by making the helical trough of the mandrel shallower. Manufacturing equipment. 2. The apparatus for manufacturing a spirally corrugated plastic tube according to claim 1, wherein the narrow groove is provided with a small hole that communicates with the inside of the mandrel, and the small hole is communicated with a negative pressure source via a suitable pipe. 3 Connect the gap between the resin pipe and the mandrel outer surface before the resin pipe starts contacting the mandrel outer surface to a negative pressure source to form a negative pressure chamber, and connect the negative pressure chamber with the narrow groove to connect the communication groove to the mandrel. An apparatus for manufacturing a plastic pipe with spiral corrugations according to claim 1 provided on the outer circumferential surface. 4. The apparatus for manufacturing a spirally corrugated plastic tube according to claim 1, 2, or 3, wherein the narrow groove is a plurality of loop-shaped narrow grooves. 5. The spirally corrugated plastic tube according to claim 1, 2, or 3, wherein the narrow groove is a plurality of loop-shaped grooves, and a bridge groove is provided to communicate the loop-shaped grooves with each other. manufacturing equipment. 6 Claim 1, in which the thin groove is a coiled thin groove,
The apparatus for manufacturing a spirally corrugated plastic pipe according to item 2 or 3.