JP3212356B2 - Extrusion molding method of synthetic resin tube with inner spiral rib - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extruding a synthetic resin tube having an internal spiral rib.

[0002]

2. Description of the Related Art As a method for continuously producing a synthetic resin pipe with an internal spiral rib used as a vertical drainage pipe of a building, a production method as disclosed in Japanese Patent Publication No. Sho 49-42670 has been proposed. In this method, as shown in FIG. 10, a thermoplastic resin tube 103 having one or two or more ridges or grooves in the longitudinal direction from the mold (die) 102 of an extruder 101 is continuously connected to the inner surface of the tube. Extrude. Then, the extruded softened tube 103 is immediately put into the outer diameter former 1.
04 and a cooling jacket 105 provided on the outside of the pipe 103, while cooling the outer diameter of the pipe 103 while regulating the outer diameter thereof. Like that.

[0003] That is, the outer diameter former 104 is
02 prevents the expansion of the pipe 103, and the cooling jacket 10 of the outer diameter former 104.
5 cools the tube surface rapidly so that the tube surface is not deformed. Then, when the pipe 103 is pulled while being twisted, the inner surface side of the pipe 103 is twisted, and a ridge or a concave groove is formed into a spiral shape.

[0004]

However, in the above method, since the softened portion of the tube 103 is formed by forcibly twisting, the distortion of the outer surface of the tube> the distortion of the inner surface of the tube> the distortion of the central portion of the tube. There is a difference in distortion remaining on the outer and inner surfaces of the tube, referred to as distortion. Therefore, deformation such as twisting easily occurs after piping. Also, particularly, when hot waste water flows down in the pipe, the temperature of the pipe rises and the elastic modulus decreases, so the pipe tries to return to the state in the extrusion die, that is, the straight pipe state without ridges or grooves. .

That is, the helical ribs and grooves become small, and a predetermined drainage capacity may not be obtained. In view of such circumstances, the present invention does not cause deformation such as torsion after piping, or the spiral rib does not become small due to the influence of hot drainage flowing through the inside, and the drainage capacity is semipermanently impaired. It is an object of the present invention to provide a method for extruding a synthetic resin tube having no internal spiral ribs.

[0006]

According to the present invention, there is provided a method for extruding a synthetic resin pipe having an inner spiral rib according to the present invention. A synthetic resin tube was continuously extruded while extruding a portion of the core having at least a concave groove formed from an extrusion die provided on the surface by the same number as the number of spiral ribs while rotating the core at a constant speed around the tube axis. The pipe was synchronized with the extrusion speed of the pipe in the pipe axis direction and the rotation speed of the pipe in the circumferential direction, and was taken up by a rotary take-off machine.

In the above configuration, first, the tubular molten resin (hereinafter, “parison”) is extruded from the mold while rotating in the same direction as the rotation direction of the core by the rotation of the rotating portion of the core. Since the parison extruded from the mold is kept in a softened state, it is shaped into a synthetic resin tube with an internal spiral rib of a predetermined diameter through a forming tube with a cooling tank before being taken by a rotary take-up machine, and cooled and solidified. The outer diameter of the tube is different from the outer diameter of the parison when it is pulled by the rotary puller. Therefore, to pull the extruded pipe in synchronization with the extrusion speed of the pipe in the pipe axis direction and the rotation speed of the pipe in the circumferential direction, and to pull the extruded pipe by the rotary take-off machine, means that the extrusion speed of the parison is Xcm / min. Assuming that the speed is Yrpm, the take-up speed of the rotary take-up machine is set to (X + α) cm / min in the tube axis direction, and the rotational speed is set to Yrpm.

Here, α is a function determined by the modulus of elasticity of the molten resin, and the smaller the value, the smaller the deformation during use of the tube. However, in the case of hard vinyl chloride, α = X ×
(1/200 to 1/10). When the outer diameter of the pipe to be manufactured is much smaller than the parison, α = X
It may be set to about 1/5. In addition, it is preferable that the forming tube has a structure in which the spiral movement of the outer peripheral surface of the synthetic resin tube exerts as little resistance as possible.

Further, as a synthetic resin for forming the tube,
Although not particularly limited, for example, polyvinyl chloride, post-chlorinated polyvinyl chloride, polyethylene, nylon and the like can be mentioned, and a synthetic resin having an apparent viscosity of 1000 poise or more is particularly preferable. That is, when the apparent viscosity is less than 1000 poise, the molten resin is not smoothly guided to the groove,
The molten resin that has once entered the concave groove is extruded into a part without the groove. Therefore, there is a possibility that irregularities may be formed in a portion of the inner surface of the tube that should be smooth, that is, a portion where the rib is not formed, a discontinuous rib may be formed, or the rib may be crushed. In addition, since the viscosity is low even after being extruded, the parison (resin in a semi-molten state) tends to draw down easily, and tends to be difficult to form into a perfect circular tube.

In general, even if the apparent viscosity of a resin is less than 1000 poise, the apparent viscosity can be reduced to 1000 poise by blending calcium carbonate or the like into the resin or by utilizing chemical crosslinking with a silane coupling agent or the like. The above can be adjusted. Although not particularly limited, the concave groove is preferably gradually deepened at an inclination angle of 30 to 60 degrees toward the outlet side of the core, and then preferably has a constant depth.

The cross-sectional shape of the concave groove is not particularly limited as long as the opening of the groove is wider than the bottom. Examples of the cross-sectional shape include a substantially V shape, a substantially U shape, and a substantially semicircular shape. The length may be arbitrary, but is 1/20 to 1/5 with respect to the inner diameter of the tube.
About 0 is preferable, and about 1/25 to 1/35 is particularly preferable. The number of concave grooves differs depending on the use of the pipe to be manufactured and is not particularly limited. For example, when manufacturing a pipe with an inner spiral rib having an inner diameter of 80 to 200 mm used as a vertical drainage pipe for a building, the number of grooves is 8 to 15. It is preferable to arrange them evenly around the circumference.

[0012]

According to the above construction, the synthetic resin tube is continuously extruded from the mold at a predetermined speed in the tube axis direction.
At the same time, a helical rib is formed inside with the rotation of the concave groove forming portion of the core, and the core is extruded from the extrusion die while rotating. And by pulling out the pipe extruded by the take-up machine in the circumferential direction in synchronization with the extrusion speed and the rotation speed, a load such as torsion is not applied to the softened parison portion of the extruded pipe. .

Therefore, it is possible to continuously form a synthetic resin tube having an inner spiral rib with no large distortion remaining and no difference in distortion inside and outside the tube.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. As shown in FIG. 1, in the extrusion molding method of this embodiment, the molten resin is continuously fed from the extruder 1 to the mold 2 and the exit of the mold 2 is performed in the same manner as in the ordinary continuous extrusion molding method of a synthetic resin tube. , A softened parison 51 is continuously extruded, immediately passed through a forming tube 3 with a cooling tank, the outer diameter is adjusted, and the solidified material is cooled and solidified into a tube 5 having a desired shape. It is designed to take over. The pipe 5 taken by the take-up machine 4 is cut into a predetermined length by a cutting machine 6 and sent to a discharger 7.

The mold 2 is, as shown in FIGS. 2 and 3,
Fixed land 21, fixed core 22, rotating core (tip core) 23, rotating shaft 24, adapter ring 25
It has. As shown in FIGS. 4 to 6, the fixed core 22 is provided with a flange 22b and an oilless bearing 22c with the main body 22a interposed therebetween.
Are provided along the center axis of the rotary shaft 24. A step-down portion 22e is formed on the surface of the main body 22a.

As shown in FIGS. 7 and 8, the rotary core 23 includes a main body 23a and an oilless bear rig 23b provided on an end surface of the main body 23a on the fixed core 23 side. A plurality of main bodies 23a (8 in FIG.
The groove 23c is formed, and an insertion hole 23d of the rotary shaft 24 is provided along the central axis.

The concave groove 22a is gradually deepened from the molten resin inlet side, and is provided in parallel to the outlet of the mold 2 when reaching a certain depth. And fixed core 2
2 and the rotating core 23, the rotating shaft 24 is inserted through the insertion holes 22d and 23d, and the nut 2 is inserted into the rotating shaft 24.
7, the two oil-less bearings 22c, 2 which are firmly sandwiched between the detents 26 and face each other.
3c is slidably pressed. In addition, as shown in FIG. 2, the rotary shaft 24 has oil-less bearings 22f, 22f, and 22 in the insertion holes 22d of the fixed core 22.
In addition to being rotatably supported by f, a key (not shown) is driven into a key groove 23e of the rotating core 23, whereby the rotating core 23 is integrally rotated.

Therefore, as shown in FIGS. 1 and 2, when the rotary shaft 24 connected to the motor 8 via the chain 81 rotates, only the rotary core 23 rotates smoothly with the rotation of the rotary shaft 24. . Moreover, since the fixed core 22 and the rotating core 23 are pressed against each other via the oilless bearings 22c and 23c, the molten resin does not enter the gap or the like.

As shown in FIG. 2, the fixed land 21 surrounds the fixed core 22 and the rotating core 23 from outside.
Stepped portion 22e of fixed core 22 and rotating core 23
A flow path (resin passage portion) 28 of the molten resin extruded from the extruder 1 is formed between the fixing core 22 and the fixed core 22 by being bolted to the flange 22b.

The adapter ring 25 is fixed to the fixed land 21.
And is an injection port for injecting the molten resin extruded from the extruder 1 into the mold 2.
The take-up machine 4 can take the pipe 5 at an arbitrary take-up speed in the pipe axis direction of the pipe 5 and can simultaneously rotate the pipe 5 at an arbitrary speed in the circumferential direction. ing.

Each of the oil bearings 22c, 22
The materials of f and 23c include metals, alloys, ceramics and the like, and can be freely selected in consideration of a tube forming temperature (normally 160 to 300 ° C.), a rotation speed, abrasion resistance and the like. As described above, the molten resin sent from the extruder 1 to the mold 2 is, as shown in FIG.
The first resin passing portion 29a formed between the stepped portion 22e provided on the surface of the main body 22a and the fixed land 21 and the second resin formed between the rotating core 23 and the fixed land 21 are next formed. The parison 51 is pushed out of the mold 2 through the resin passage portion 29b.
3 is extruded while rotating in a certain direction, so that the spiral rib corresponding to the concave groove 23c provided in the rotating core 23 is extruded while rotating in the circumferential direction while being formed therein.
That is, the parison 51 is pushed out of the mold 2 in a hanging state without applying a twist to the portion of the parison 51 in which the tube 5 is softened as in the conventional case, and at the same time, a spiral rib is formed on the inner surface.

The parison 51 enters the forming tube 3 with a cooling bath from the mold 2 and is cooled and solidified while being shaped to form a synthetic resin tube 5 with an inner spiral rib having a desired diameter, and is taken off by the take-up machine 4. However, the take-up machine 4 takes out the mold 2 in the tube axis direction at substantially the same speed as the extrusion speed, and gives the tube 5 a circumferential rotation in accordance with the rotation speed of the tube 5. . Therefore, no load is applied to the softened portion of the pipe 5 by the take-off by the take-off machine 4.

That is, according to this method, forcible twist is not applied to the softened portion of the tube 5 unlike the conventional method, and there is no distortion inside and outside the tube 5 as shown in FIG. It is possible to obtain a synthetic resin tube 5 with an internal spiral rib in which a plurality of spiral ribs 52 are formed on the internal surface. By the way, 3 of the circumference
12 V-shaped grooves with a width of 5 mm and a depth of 3 mm every 0 degree
The rotating core 22 having a length of 75 mm and the fixed land 21 are provided.
Using the above-mentioned molding apparatus with a clearance of 2 mm, a pipe 5 with an inner spiral rib made of PVC (polyvinyl chloride) having an inner diameter of 100 mm was extruded at a rate of 30 kg / h and the rotation speed of the rotary core 23 was 0.1 to 2.0 rpm. Toro 1 formed by changing with
A helical rib having a free pitch in the range of 10 to 10 m was formed. Moreover, the rib formed on the inner surface of the tube had a height of 2.6 to 2.9 mm, and the cross-sectional shape was substantially the same as the cross-sectional shape of the concave groove.

Further, while extruding the molten resin 11 at an extrusion rate of 12 kg / h, the rotation speed of the rotating core 23 is 0.5 rpm.
(1.7 rpm), the parison is 17 cm
Minute (20 cm / min), the rotation speed was 0.13 rpm (0.16 rpm), and the spiral rib pitch of the tube with the internal spiral rib obtained at this time was 135 cm (128 cm). In the method of the present invention, it is necessary to adjust the speed of the molten resin in the tube axis (extrusion) direction to be constant before the molten resin enters the second resin passage portion 29b.

That is, if the speed cannot be adjusted as described above, the speed of the molten resin increases and decreases in the circumferential direction of the tube in the second resin passage portion 29b, and the formed tube 5 with the inner spiral ribs is Bent in a certain direction or spiral (coiled)
It becomes bent and the product value drops. Therefore, in the mold 2 of this embodiment, the stepped portion 22e is provided with the island-shaped portion 22g, and the molten resin 11 sent from the extruder 1 into the mold 2 is indicated by an arrow in FIGS. By bypassing the island-shaped portion 22g, it can be immediately pushed out at a constant speed in the pipe axis direction.

The method for extruding a synthetic resin tube having an inner spiral rib according to the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the detent 26 is fitted on the rotating shaft 24 and the fixed core 22 is
And the rotating core 23,
Instead of the rotation stopper 26, a bulging portion serving as a stopper may be provided directly on the rotating shaft 24.

[0027]

According to the present invention, since the extrusion method for a synthetic resin tube having an inner spiral rib according to the present invention is constituted as described above, a load such as torsion is not applied to the softened portion of the extruded tube. Thus, a synthetic resin tube with an inner spiral rib can be obtained. Therefore, the obtained synthetic resin pipe with internal spiral ribs has no large distortion left, and there is no difference in distortion between the inside and outside of the pipe, causing deformation such as twisting after piping, and hot drainage flowing inside. Does not make the spiral ribs smaller.

That is, if this synthetic resin pipe is used as a vertical pipe for drainage of a building such as a middle-rise or high-rise building, the ability to effectively attenuate the flow rate of drainage and ensure sufficient ventilation in the center of the pipe is semi-permanent. Not be impaired.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an apparatus for manufacturing a synthetic resin pipe used for carrying out a method for extruding a synthetic resin pipe with an inner spiral rib according to the present invention.

FIG. 2 is a cross-sectional view illustrating a mold of the manufacturing apparatus of FIG.

FIG. 3 is a view of the mold in FIG.

FIG. 4 is a front view of a fixed core of the mold of FIG. 2;

FIG. 5 is a view of the fixed core of FIG.

6 is a view in the direction of the arrow of the fixed core of FIG. 4;

FIG. 7 is a front view of a rotary core of the mold of FIG. 2;

8 is a view in the direction of arrow D of the rotary core of FIG. 7;

FIG. 9 is a cross-sectional view illustrating an example of a synthetic resin tube with an internal spiral rib obtained by the extrusion molding method for a synthetic resin tube with an internal spiral rib according to the present invention.

FIG. 10 is an explanatory view showing a method of manufacturing a known synthetic resin tube having an internal spiral rib.

[Explanation of symbols]

 2 mold 4 take-off machine 5 synthetic resin tube 22 fixed core 23 rotating core 23c concave groove 52 spiral rib

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-293909 (JP, A) JP-A-48-86964 (JP, A) JP-A-5-293873 (JP, A) 260420 (JP, A) JP-A-55-67419 (JP, A) JP-A-59-187418 (JP, U) JP-A-56-76420 (JP, U) JP-B-49-42670 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 47/00-47/96

Claims (1)

(57) [Claims] 1. A method for extruding a synthetic resin pipe having an inner spiral rib, wherein a concave groove parallel to the pipe axis is provided on the outlet side surface of the core by the same number as the number of spiral ribs. The synthetic resin tube is continuously extruded while rotating at least the portion where the concave groove is formed around the tube axis at a constant speed, and the extruded tube is extruded at a speed in the direction of the tube axis and rotates in the circumferential direction of the tube. A method for extruding a synthetic resin tube with internal spiral ribs, wherein the synthetic resin tube is taken in with a rotary take-off machine in synchronization with the speed.