JPS5831290B2 - Manufacturing equipment for spirally corrugated plastic pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When extrusion molding a resin pipe using a polyolefin resin such as polyethylene, polypropylene, polycarbonate resin, or other general thermoplastic resin, the present invention fixes a mandrel and attaches it to the inner peripheral surface of the mandrel. A spirally corrugated plastic tube with smooth inner and outer surfaces and excellent mechanical properties such as lateral pressure resistance and bending resistance. Regarding the manufacturing method.

There are various known methods for manufacturing spirally corrugated plastic pipes, but the most common one is to put a resin pipe into a desired mold, apply heat and apply air pressure inside the pipe, and mold the pipe into the spirally corrugated shape of the mold. A molding method is known in which the material is crimped onto an inner wall.

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

In addition, 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 expense. Moreover, it has the disadvantage that it can only be used for short lengths.

A method using a so-called mandrel has been developed which solves the above-mentioned drawbacks, allows continuous molding of a long object in one piece, and which 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 released from the extruder. The resin tube 6 is extruded onto the outer peripheral surface of the mandrel 4 by heating and melting, and the gap 8 between the resin tube 6 and the mandrel 4 is filled with a negative pressure source ( (not shown) to create negative pressure and suction, align the resin tube 6 along the outer peripheral surface of the mandrel 4,
This is a method in which the mandrel 4 is rotated while being cooled and the resin tube 6 is sequentially sent forward by its spiral waveform portion.

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 circumferential surface has a spiral waveform and has a slope, contraction in the length direction becomes contraction in the direction along the slope, and is regulated by the top of the spiral, so both slopes sandwiching the valley. As a result, the troughs of the resin tube separate from the outer peripheral surface of the mandrel, and as the slope continues to contract toward the top, the troughs become constricted, and the inner periphery of the troughs becomes constricted. Uneven wrinkles may occur, and since the troughs on the inner circumferential surface of the tube 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.

Therefore, it is uneconomical to increase the wall thickness.

Further, during use, fluid flow may be poor, and dirt, mud, etc. may easily accumulate in the wrinkled portions, leading to blockage of the pipe.

It has drawbacks such as being unsightly and significantly reducing its commercial value.

Furthermore, in Japanese Patent Publication No. 51-46529, as a general method for manufacturing resin pipes, a fixed mandrel method is used in which the resin pipe is rotated in the circumferential direction of the fixed mandrel while being drawn along the outer peripheral surface of the fixed mandrel. It 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. This is not sufficient to create a spiral wave, and uneven wrinkles are produced on the inner surface of the trough of the spiral.

As a result of various studies in order to solve the above-mentioned drawbacks, the inventors of the present invention have provided a mandrel on the outer circumferential surface of the resin pipe to facilitate cooling and connection with a vacuum pump, and to make the connection with a vacuum pump easier after the resin pipe comes into contact with the mandrel. The above disadvantages are solved by applying negative pressure to the gap between the resin tube and the mandrel in a certain section until it cools and solidifies, making the resin tube tightly adhere to the mandrel in that section. By pulling the resin, the molecules can be arranged in a helical direction, and we have come up with the idea of obtaining a resin tube with excellent mechanical properties.

That is, the object of the present invention is to provide a spiral wave-shaped inner circumferential surface on the inner circumferential surface of the extruded semi-molten resin tube at the front of the extruder mouthpiece in the resin extrusion direction. A mandrel is fixedly installed, the inner peripheral surface of the mandrel is formed into a slightly tapered shape, and the extruded resin pipe begins to come into contact with the inner peripheral surface of the mandrel and is rapidly cooled.
A narrow groove that intersects with the spiral of the mandrel and has a circumferential angle of 360 or more is provided on the inner circumferential surface of the mandrel in a narrow area extending all around the circumferential direction of the inner circumferential surface of the mandrel. The outer surface of the peak of a resin pipe connected to a negative pressure source and extruded into the valley of the spiral on the inner circumferential surface of the mandrel beyond the narrow area provided with the narrow groove, with the valley of the spiral of the mandrel being made shallow. A take-up device is provided with a seal part that comes into contact with the mandrel, and takes over the resin pipe extruded along the inner circumferential surface of the mandrel while rotating it in the circumferential direction in accordance with the extrusion speed of the resin pipe and the helical pitch of the mandrel. An object of the present invention is to provide an apparatus for manufacturing a plastic pipe with spiral corrugations.

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 to the tip of the extruder; 16 indicates a mandrel fixed to the die 12 through a heat insulating packing 18 in the forward direction of extrusion; and 20
2 is an extruded resin pipe, and 22 is a take-up roll.

The mandrel 16 has a spirally corrugated inner circumferential surface, and the inner circumferential surface is slightly tapered.

The purpose of this taper is to facilitate the removal of the resin tube 20.

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 24 is discharged from the water inlet 26 through the outlet 26.

28 is a plurality of loop-shaped thin grooves, which are connected to the resin pipe 20.
is provided along the circumferential direction of the inner circumferential surface of the mandrel 16 within a certain section from the vicinity where it starts to contact the inner circumferential surface of the mandrel 16 and intersects with the spiral of the mandrel.

The above section is the section from when the resin tube 20 begins to come into contact with the inner circumferential surface of the mandrel 16 until it cools and solidifies to some extent, and although it varies depending on the type of resin, the thickness and diameter of the resin tube, and the cooling conditions, etc., it is usually 5 to 1 for cooling by water cooling
0CrIL is preferred.

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

36 is a cooling mechanism that cools the resin tube by water cooling or air cooling.

The take-up roll 22 uses 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 20 from three sides to adjust the speed of the spiral.
Rotate in the direction of the arrow in synchronization with the extrusion speed of 0.

In addition, to show another embodiment of the narrow groove 28, the loop-shaped narrow groove 2
8 may not be provided with the bridge groove 30, but each of the loop-shaped narrow grooves may be provided with a small hole 32 and connected to a vacuum pump.

In addition, as shown in FIG. 3, the gap 38 between the resin tube 20 and the mandrel 16 before the extruded resin tube 20 contacts the inner peripheral surface of the mandrel 16 is connected to the pipe 40 communicating with the gap 38 using a vacuum pump. (not shown) to create negative pressure, and the loop-shaped narrow groove 28 and the bridge groove 30 (without small holes) may be communicated with the void 38 through the communication groove 42.

Further, as shown in FIG. 4, the thin groove 28 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.

As shown in FIG. 5, a seal portion 44 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-described configuration, first, cooling water is circulated through the mandrel through the water inlet 24, the thermoplastic resin is heated and melted, and the resin tube 20 is inserted into the mandrel 16 through the annular slit 14. Extrude onto the inner circumferential surface of.

Since the resin tube 20 contacts the mandrel 16 and its outer peripheral surface is cooled and contracts, it rises to the inner peripheral surface of the mandrel 16 and moves along the inner peripheral surface.

At this time, the resin pipe 20 passes through the small hole 32 and the narrow groove 28.
Since the gas existing in the gap between the mandrel 16 and the mandrel 16 is discharged, the resin tube 20 advances in close contact with the inner circumferential surface of the mandrel 16 within a certain section defined by the narrow grooves 28.

In this case, it is preferable to apply air pressure from the distal end direction of the extruded resin tube 20 to achieve better adhesion.

In the embodiments shown in FIGS. 3 and 4, the negative pressure is
8 and performs similar functions.

Furthermore, by arranging the seal portion 44 as shown in FIG. 5, air is prevented from entering along the troughs of the spiral from the tip of the mandrel 16, which has a thicker tip, and from the thin groove 28 onward. Negative pressure is applied to the troughs of the spiral, and the resin tube is molded in close contact with the inner circumferential surface of the mandrel, at least within the section where the narrow grooves 28 are provided.

The resin tube is cooled and solidified to some extent in the section of the narrow groove 28, and is further water-cooled or air-cooled by the mandrel 16 and the cooling mechanism 36 to be completely solidified.

The take-up roll 22 has a helical waveform on its outer peripheral surface with the same pitch as the helical pitch of the mandrel 16, and the traveling speed of the wave rotates in synchronization with the extrusion speed of the resin pipe 20.
The resin pipe 20 is taken out while rotating like a screw.

At this time, the resin tube 20 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 outside of the resin tube 20 and is supported by its helical waveform, and Since the resin tube ahead of the narrow groove 28 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 with a thicker end, the resistance to take-up of the resin pipe is small, and since the seal part that makes the trough of the spiral shallower is provided, the mandrel is formed with a thicker end. Negative pressure extends into the troughs of the spiral, ensuring that the resin tube is in close contact with the inner circumferential surface of the mandrel within the narrow area where the groove exists, resulting in extremely good formability, and due to the reliable polishing action of the groove. You can get resin tubes with beautiful skin.

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

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 DESCRIPTION OF THE DRAWINGS] 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 sectional view of the mandrel. shows. 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 sectional 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...
...Insulation packing, 20...Resin pipe, 22...
... Take-up roll, 24 ... Water inlet, 2
6...Discharge port, 28...Small groove, 30.
...Bridge groove, 32...Small hole, 34.
...Pipe, 36...Cooling mechanism, 38.
...Gap, 40...Pipe, 42...
...Communication groove, 44... Seal portion.

Claims (1)

[Scope of Claims] 1. A mandrel having a spiral wave-shaped inner circumferential surface, on which the extruded semi-molten resin tube is extruded, is provided in front of the die of the extruder in the direction of resin extrusion. The inner circumferential surface of the mandrel is fixedly installed, and the inner circumferential surface of the mandrel is formed into a slightly tapered shape. A narrow groove that intersects the spiral of the mandrel and has a circumferential angle of 360° or more is provided on the inner circumferential surface of the mandrel in a narrow area extending over the entire circumference, and the narrow groove is connected to an appropriate negative pressure source. , a sealing portion is provided within the spiral trough on the inner circumferential surface of the mandrel ahead of the narrow area where the narrow groove is provided, the helical trough of the mandrel being made shallower and abutting against the outer surface of the crest of the extruded resin tube. The method is characterized by being provided with a take-off device that takes over the resin pipe extruded along the inner circumferential surface of the mandrel while rotating it in the circumferential direction in accordance with the extrusion speed of the resin pipe and the helical pitch of the mandrel. Manufacturing equipment for plastic pipes with spiral waves. 2. The apparatus for manufacturing a spirally corrugated plastic tube according to claim 1, wherein the narrow groove is provided with a small hole communicating with the outside of the mandrel, and the small hole is communicated with a negative pressure source via a suitable pipe. 3 A gap between the resin tube and the mandrel inner circumferential surface before the resin tube starts to come into contact with the mandrel inner circumferential surface is connected to a negative pressure source to form a negative pressure chamber, and a communication groove that communicates the negative pressure chamber with the narrow groove. An apparatus for manufacturing a spirally corrugated plastic tube according to claim 1, in which: is provided on the inner circumferential surface of the mandrel.Claims 1 and 2, in which the narrow groove is a plurality of loop-shaped narrow grooves. Or the apparatus for manufacturing a spirally corrugated plastic pipe according to item 3. 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.