JPS5831289B2 - Manufacturing equipment for spirally corrugated plastic pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides polyolefin resins such as polyethylene,
When extrusion molding a resin pipe using polycarbonate resin or other general thermoplastic resin as a material, a mandrel is fixed, and the resin pipe is rotated and taken out while keeping the resin pipe in close contact with the outer circumferential surface of the mandrel. This invention relates to a method for producing a spirally corrugated plastic tube that has smooth inner and outer surfaces and excellent mechanical properties such as lateral pressure resistance and bending resistance.

Conventionally, various methods of manufacturing spirally corrugated plastic pipes are known.

In general, a resin pipe is placed in the desired mold,
A molding method is known in which air pressure is applied inside the tube while heat is applied to press the tube against the spirally corrugated inner wall of a mold.

However, this method is complicated, 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 cost. 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 peripheral surface is attached to the extruder so as to be rotatable in the circumferential direction in front of the extruder nozzle 2 in the extrusion direction, and the thermoplastic resin is transferred from the extruder to the extruder. is heated and melted and extruded as a resin tube 6 onto the outer peripheral surface of the mandrel 4, and the gap 8 between the resin tube 6 and the mandrel 4 is filled with a negative pressure source ( (not shown), the resin tube 6 is connected to a negative pressure and suction is applied, the resin tube 6 is placed along the outer peripheral surface of the mandrel 4, the mandrel 4 is rotated while being cooled, and the resin tube 6 is sequentially sent forward by its spiral waveform. It is.

However, according to this method, once the resin tube has made contact with the outer circumferential surface of the mandrel, the suction force due to negative pressure does not reach the outer circumferential surface of the mandrel. However, since the outer peripheral surface has a spiral waveform and has a slope, the contraction in the length direction is contraction in the direction along the slope, and is restricted by the top of the spiral, so the side slopes sandwiching the valley. As a result, the troughs of the resin tube separate from the outer circumferential surface of the mandrel, and as the constriction continues toward the top of the slope, the troughs constrict and the inner circumferential surface of the troughs becomes uneven. Also, since the valleys on the inner circumferential surface of the tube do not come into contact with the mandrel, they are not polished due to friction with the mandrel, resulting in only the valleys becoming rough.

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

In addition, during use, fluid flow is poor and dirt, mud, etc. tend to adhere to the pipe, which can lead to blockage of the pipe.

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

In addition, in Japanese Patent Publication No. 51-46529, a fixed mandrel method is used as a general method for manufacturing resin pipes, in which the resin pipe is rotated in the circumferential direction while being drawn along the outer peripheral surface of the fixed mandrel. is taken.

In this case, a groove is provided on the outer circumferential surface of the mandrel in the vicinity where the resin tube starts to contact the outer circumferential surface of the mandrel, and suction is applied through a small hole drilled in the groove to bring the resin tube into contact with the mandrel. In order to form a perfect helical waveform, the above-mentioned degree of contact is insufficient, and uneven wrinkles also occur on the inner surface of the spiral trough.

As a result of various studies to solve the above-mentioned drawbacks, the inventor of the present invention has found that after the resin tube contacts the mandrel, the gap between the resin tube and the mandrel is made to have a negative pressure in a certain section until the resin tube is cooled and solidified to some extent. The above-mentioned drawbacks were solved by tightly adhering the resin tube to the mandrel, and by drawing the resin tube while rotating it with respect to the mandrel, the molecules were aligned in a certain direction, and it was thought that a resin tube with excellent mechanical properties could be obtained.

That is, an object of the present invention is to provide a mandrel having a spirally wave-shaped outer peripheral surface in front of the mouthpiece of an extruder in the direction of resin extrusion, cool the mandrel, and release a semi-molten resin pipe from the mouthpiece of the extruder. In the apparatus for manufacturing a spirally corrugated plastic tube, the mandrel is fixed to a die or the like in front of the die in the direction of resin extrusion, and has a taper that tapers slightly toward the tip. A helical spiral and Providing narrow grooves that intersect and have a circumferential angle of 360° or more,
The narrow groove is connected to an appropriate negative pressure source, and the resin is extruded into the spiral valley on the outer peripheral surface of the mandrel beyond the narrow area where the narrow groove is provided by making the spiral valley of the mandrel shallow. A seal part is provided that contacts the inner surface of the trough of the spiral of the tube, and the resin tube extruded along the outer peripheral surface of the mandrel is rotated in the circumferential direction in accordance with the extrusion speed of the resin tube and the pitch of the spiral of the mandrel. To provide an apparatus for manufacturing a spirally corrugated plastic tube, which is characterized by being equipped with a taking-off device.

Embodiments of the present invention will be described in detail below with reference to the drawings.

In Fig. 2, reference numeral 12 indicates a die having an annular slit 14 and is fixed at the tip of the extruder, and 16 indicates a die 1 located forward in the extrusion direction.
2 is a mandrel fixed to the inner mold, 18 is an extruded resin pipe, and 20 is a take-up roll.

The mandrel 16 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 8% in this example.

Cooling water is circulated within the mandrel 16, and the cooling water 22 is discharged from the water inlet 24 through the outlet 24.

26 is a plurality of loop-shaped thin grooves, which are connected to the resin pipe 18.
is provided on the outer circumferential surface of the mandrel 16 within a certain section from the vicinity where it starts contacting the outer circumferential surface of the mandrel 16 along the circumferential direction thereof and intersects with the spiral of the mandrel.

The above section is the period from when the resin tube 18 begins to come into contact with the outer circumferential surface of the mandrel 16 until it cools and solidifies to some extent, and varies depending on the type of resin, the thickness and diameter of the resin tube, and the cooling conditions, etc. 5~10c for water cooling
The rI1 position is preferred.

Reference numeral 28 denotes a bridge groove that communicates the loop-shaped narrow grooves 26 with each other. A small hole 30 is bored in this bridge groove 28, and the bridge groove 28 is connected to a vacuum pump (not shown) through a pipe 32.

A cooling mechanism 34 cools the resin pipe by water cooling or air cooling.

The take-up roll 20 is a rubber roll or the like with a spiral shape having the same pitch as the spiral of the mandrel 16, and pinches the resin tube 18 from three sides, and synchronizes the traveling speed of the spiral waves with the extrusion speed of the resin tube 18. and rotate in the direction of the arrow.

In another embodiment of the narrow groove 26, the loop groove 26 may not be provided with the bridge groove 28, and each of the loop grooves may be provided with a small hole 30 to be connected to a vacuum pump.

Further, as shown in FIG. 3, the resin pipe 18 before the extruded resin pipe 18 contacts the outer peripheral surface of the mandrel 16
A pipe 38 communicating with the gap 36 is connected to a vacuum pump (not shown) to create a negative pressure in the gap 36 between the mandrel 16 and the loop groove 26 and the bridge groove 28 (without small holes). may be communicated with the void 36 through the communication groove 37.

Further, as shown in FIG. 4, the thin groove 26 may be a coiled thin groove having a circumferential angle of 360° or more, and communicate with the gap shown in FIG. 3 to create a negative pressure, or A small hole may be bored and connected to a vacuum pump as shown in FIG.

Further, as shown in FIG. 5, a seal portion 40 is provided in the spiral trough near the tip of the mandrel 16 to make the trough slightly shallower.

To obtain a spirally corrugated plastic tube with the above configuration, first, cooling water is circulated through the water inlet 22 into the mandrel 16, and the thermoplastic resin is heated and melted to form the annular slit 1.
4, the resin tube 18 is extruded onto the outer peripheral surface of the mandrel 16.

The resin tube 18 advances along the outer peripheral surface of the mandrel 16 while being cooled and solidified.

At this time, the gas existing in the gap between the resin tube 18 and the mandrel 16 is discharged through the small holes 30 and the narrow grooves 26, so that the resin tube 18 is moved from the outer circumferential surface of the mandrel 16 within a certain section defined by the narrow grooves 26. 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 26.
and perform similar functions.

Furthermore, if a seal portion 40 is provided as shown in FIG.
Air is prevented from entering along the spiral trough from the tapered tip of the mandrel 16, and negative pressure extends from the narrow groove 26 to the tip of the spiral trough, and the resin tube is moved at least along the narrow groove 2.
The molding is surely carried out in close contact with the outer peripheral surface of the mandrel within the section where 6 is provided.

In the section of the narrow groove 26, the resin pipe 18 is cooled and solidified to some extent, and the mandrel 16 and the cooling mechanism 3 are further cooled and solidified.
4, it is completely solidified.

The take-up roll 20 has a helical waveform on its outer peripheral surface with the same pitch as the mandrel 16 and the spiral, and the traveling speed of the wave rotates in synchronization with the extrusion speed of the resin pipe 18.
The resin pipe 18 is taken out while rotating like a screw.

At this time, the resin tube 18 is twisted spirally from the time it is extruded from the mouthpiece 12 until it comes into contact with the mandrel 16, but the mandrel 16 comes into contact with the inside of the resin tube 18 and is supported by its spirally corrugated outer peripheral surface. Since the resin tube ahead of the narrow groove 26 at the contact portion with the mandrel 16 is cooled, it will not be deformed.

In this way, a resin tube having a helical waveform on both the inner and outer surfaces and twisted in a helical direction is obtained.

As described above, according to the present invention, since the mandrel is formed in a tapered manner, the pulling resistance of the resin tube is small, and since the seal portion is provided to make the trough of the spiral shallower, it is possible to Negative pressure extends into the troughs of the spiral, ensuring that the resin tube is in close contact with the outer circumferential surface of the mandrel in the narrow area where the groove exists, resulting in extremely good moldability, and the reliable polishing action of the groove makes it beautiful. You can get a resin tube with a nice skin.

Moreover, it is possible to obtain a resin tube with excellent strength in which the resin is oriented.

Although various preferred embodiments of the present invention have been described above, 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 partially cutaway side 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... Mandrel, 18...
...Resin pipe, 20...Take-up roll, 22...
...Water inlet, 24...Drain port, 26...
...Narrow groove, 28...Bridge groove, 30...
...Small hole, 32...Pipe, 34...
・Cooling mechanism, 36... air gap, 31...
Communication groove, 38... pipe, 40... seal portion.

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 resin extrusion direction, the mandrel is cooled, and a semi-molten resin tube is passed from the extruder mouthpiece to the outer peripheral surface of the mandrel. In an apparatus for manufacturing a spirally corrugated plastic tube that is formed by upward extrusion, the mandrel is fixed to a mouthpiece or the like in front of the mouthpiece in the direction of resin extrusion, and is formed into a tapered mandrel that tapers slightly toward the tip. and intersects with the spiral of the mandrel on the outer circumferential surface of the mandrel within a narrow area extending over the entire circumference of the outer circumferential surface of the mandrel, where the extruded resin pipe begins to contact the outer circumferential surface of the mandrel and is rapidly cooled. , a narrow groove having a circumferential angle of 360° or more is provided, the narrow groove is connected to an appropriate negative pressure source, and the groove is placed in the spiral valley on the outer circumferential surface of the mandrel beyond the narrow area where the narrow groove is provided. , the spiral valley of the mandrel is made shallow and a seal part is provided that contacts the inner surface of the spiral valley of the extruded resin pipe, and the resin pipe extruded along the outer peripheral surface of the mandrel is controlled by the extrusion speed of the resin pipe and the mandrel. 1. A manufacturing device for a helical corrugated plastic tube, characterized in that the device is equipped with a take-off device that rotates the tube in the circumferential direction according to the pitch of the helix. 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 communication groove that communicates the negative pressure chamber with the narrow 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.