JP7470416B2 - Resin tube extrusion molding device and resin tube - Google Patents

Description

The present invention relates to a resin tube extrusion molding device and a resin tube.

Plastic tubes with flexible bellows-shaped sections (bends) are used as fuel pipes for vehicles, exterior materials for wire harnesses, pipes for hot water supply equipment, etc. (see, for example, Patent Document 1). The position and length of the bends in plastic tubes such as those described in Patent Document 1 are designed according to the shape of the location where the pipe is to be installed, and by bending the bends, the pipe can be installed to fit the shape of the location.

The resin tube described in Patent Document 1 is generally manufactured using a molding device called a corrugator (see, for example, Patent Document 2). However, in order to change the position and length of the bent portion depending on the location of the piping, it is necessary to change the mold used in the corrugator, which leads to increased manufacturing costs.

One technique for solving the problem of the difficulty of changing the position and length of the bent portion in a corrugator is described in, for example, Patent Document 3. Patent Document 3 describes a method in which a corrugated tube with a bellows portion formed over its entire length is molded, and then a die is used to apply heat and pressure to a portion of the bellows portion to crush it, thereby forming a straight portion and a bellows portion at any position and length.

JP 2013-243900 A JP 2014-218028 A JP 2017-221036 A

However, the method described in Patent Document 3 requires a process of crushing the bellows portion using a separate mold after molding the corrugated tube, and there is room for improvement in terms of manufacturing efficiency. In addition, resin tubes with bellows portions have the problem that they require extra piping space for the protrusions on the surface.

The present invention aims to provide a resin tube extrusion molding device that can efficiently manufacture partially bendable resin tubes, and a resin tube that can reduce piping space.

The resin tube extrusion molding device of the present invention is for molding a resin tube having a relatively low bending rigidity and a partial and multiple flexible tube section that is flexible, and includes a die for extruding supplied molten resin into a tubular shape, a first extruder for extruding a first resin, a second extruder for extruding a second resin that is softer than the first resin, a first valve provided between the first extruder and the die, a second valve provided between the second extruder and the die, and a control device capable of controlling the first valve and the second valve between a first state in which the first extruder and the die are in communication and the second extruder and the die are blocked, and a second state in which at least the second extruder and the die are in communication, and the control device controls the first valve and the second valve to switch from the first state to the second state and then switch from the second state to the first state multiple times during extrusion molding of one resin tube, thereby forming multiple flexible tube sections in one resin tube.

The resin tube of the present invention has a relatively low bending rigidity, is partially provided with flexible tube sections having flexibility, has a circular cross-sectional outer shape in a direction perpendicular to the longitudinal direction, has a constant outer diameter, and is provided with a plurality of flexible tube sections .

The present invention provides a resin tube extrusion molding device that can efficiently manufacture partially bendable resin tubes, and a resin tube that can reduce piping space.

Schematic diagram of a resin tube according to an embodiment. Schematic diagram of a resin tube extrusion molding device according to an embodiment. FIG. 3 is a partial cross-sectional view showing details of the mixing die and adjacent equipment shown in FIG.

Figure 1 is a schematic diagram of a resin tube according to an embodiment. For ease of explanation, the flexible tube portion is identified by hatching in Figure 1.

The resin tube 1 has flexible tube sections 2a-2d that have a relatively low bending rigidity and flexibility, and less flexible tube sections 3a-3e that have a relatively high bending rigidity and flexibility. The flexible tube sections 2a-2d are provided partially in the longitudinal direction of the resin tube 1, and are each sandwiched between a pair of less flexible tube sections. The flexible tube sections 2a-2d are formed from a resin that is more flexible than the resin that constitutes the less flexible tube sections 3a-3d. The flexible tube sections 2a-2d may be formed from a resin different from the resin that constitutes the less flexible tube sections 3a-3e, or may be formed from a mixed resin of the resin that constitutes the less flexible tube sections 3a-3e and a resin that is more flexible.

The resin tube 1 can be manufactured by extrusion molding using an extrusion molding device described below. Therefore, the outer diameter of the cross section of the resin tube 1 in a direction perpendicular to the longitudinal direction is a circle (a perfect circle), and the outer diameter of the resin tube is constant.

In the example of Figure 1, four flexible tube sections 2a to 2d are provided on one resin tube 1, but the number of flexible tube sections is not limited as long as it is one or more. The positions and lengths of the flexible tube sections are also not limited. The number, positions and lengths of the flexible tube sections can be changed as desired and can be set according to the shape of the piping location of the resin tube 1.

Since the resin tube 1 has flexible tube sections 2a to 2d that are partially provided, the resin tube 1 can be bent at each of the flexible tube sections 2a to 2d while maintaining the cross-sectional shape of the resin tube 1 in a substantially circular shape. Therefore, the resin tube 1 can be used for fuel piping in vehicles, exterior materials for wire harnesses, piping for hot water supply equipment, etc., and can be arranged along the piping location.

Figure 2 is a schematic diagram of a resin tube extrusion molding device according to an embodiment.

The extrusion molding apparatus 100 includes a first extruder 11, a second extruder 12, a mixing die 13, a vacuum water tank 14, an outer diameter detector 15, a take-up machine 16, a winding machine 17, and a control device 18. Each device that constitutes the extrusion molding apparatus 100 is installed on a stand.

The first extruder 11 and the second extruder 12 are, for example, screw extruders, which can melt and knead resin pellets and extrude the molten resin from the discharge port. A first resin and a second resin having different hardness are respectively supplied to the first extruder 11 and the second extruder 12. The first resin is a resin with a relatively high hardness, and the second resin is a resin that is softer than the first resin. The first resin and the second resin can be appropriately selected depending on the application of the resin tube, and for example, polyolefins such as polyethylene and polypropylene, polyamides, polyesters, fluororesins, and ABS resins can be used. It is preferable to select materials that are compatible as the first resin and the second resin, but resins with low compatibility may be selected on the condition that a compatibilizer is added. One or both of the first resin and the second resin may be appropriately blended with fillers and various additives.

The mixing die 13 is configured to mix the first resin supplied from the first extruder 11 and the second resin supplied from the second extruder 12 and extrude them into a tubular shape. Details of the mixing die 13 will be described later.

The vacuum tank 14 stores cooling water inside, and the resin extruded into a tube shape from the mixing die 13 is cooled and solidified by the cooling water. There is space inside the vacuum tank 14, but the space inside the vacuum tank 14 is maintained at negative pressure using a vacuum pump (not shown).

The outer diameter detector 15 is a device that measures the outer diameter of the resin tube 1 solidified in the vacuum water tank 14. The take-up machine 16 takes up the resin tube 1 while applying a constant tension to the resin tube 1, and sends the taken-up resin tube toward the winding machine 17. The winding machine 17 winds the resin tube 1 into a roll. Note that instead of the winding machine 17, a tube cutter that cuts the resin tube 1 to a constant length may be provided.

The control device 18 includes a computer equipped with a CPU, memory, and storage device, and controls each device that constitutes the extrusion molding device 100.

Figure 3 is a partial cross-sectional view showing details of the mixing die and adjacent equipment shown in Figure 2.

The mixing die 13 includes a die 20, a first valve 21, a second valve 22, and a kneading mechanism.

The mold 20 is a member that extrudes the supplied molten resin into a tubular shape, and includes a case 25 that serves as the outer mold, a tubular member 26 that serves as the inner mold, and a rotating member 27.

The case 25 has a hollow portion 33 corresponding to the outer shape of the tubular member 26 and the rotating member 27. The case 25 is an outer mold for extruding the resin into a tubular shape, and is a case that houses the valve bodies of the first valve 21 and the second valve 22. An extrusion port for extruding the resin is provided on the front part of the case 25. In the hollow portion 33 of the case 25, the second part 32 of the tubular member 26 and the rotating member 27 are housed adjacent to each other in order from the extrusion port side, and a predetermined gap is formed between the outer surface of the second part 32 and the inner surface of the hollow portion 33, and between the outer surface of the rotating member 27 and the inner surface of the hollow portion 33. This gap functions as a flow path that guides the supplied molten resin to the extrusion port.

In this embodiment, the portion of the case 25 that becomes the outer mold of the mold 20 and the portion that houses the valve bodies of the first valve 21 and the second valve 22 are integrally constructed, but the portion that becomes the outer mold of the mold 20 and the portion that houses the valve bodies of the first valve 21 and the second valve 22 may be constructed separately.

The tubular member 26 is a tubular member having a through hole penetrating the central axis. The through hole provided in the tubular member 26 is for introducing air into the hollow interior of the molded resin tube. The tubular member 26 includes a tubular first portion 31 including the rear end, and a ring-shaped second portion 32 connected to the first portion 31 and including the front end. The outer diameter of the first portion 31 is approximately constant. The outermost diameter of the second portion 32 is larger than the outer diameter of the first portion 31, and the second portion 32 is connected to the first portion 31 and has a cylindrical portion with a constant outer shape and a tapered portion whose outer diameter narrows toward the front end. The tubular member 26 is fixed to the case 25 by a fixing means (not shown) and is prohibited from rotating around its central axis.

The rotating member 27 is a cylindrical member having a through hole passing through the center. The inner diameter of the hollow portion of the rotating member 27 is approximately equal to the outer diameter of the first part 31 of the tubular member 26, and the first part 31 of the tubular member 26 is accommodated in the hollow portion of the rotating member 27. The outer diameter of the rotating member 27 is equal to the outer diameter of the cylindrical part of the second part 32 of the tubular member 26, and when the first part 31 of the tubular member 26 is accommodated in the hollow portion of the rotating member 27, the outer surface of the rotating member 27 and the cylindrical part of the second part 32 of the tubular member 26 form a continuous cylindrical surface. The rotating member 27 is coaxial with the tubular member 26 and is supported by the tubular member 26 so as to be rotatable around the central axis. A spiral groove is formed on the outer surface of the rotating member 27. The rotating member 27 is connected to the motor 28 and constitutes a kneading mechanism together with the motor 28. The rotating member 27 rotates by the driving force of the motor 28. The resin supplied to the space between the rotating member 27 and the inner surface of the hollow part of the case is kneaded by the grooves on the outer surface of the rotating member 27 as the rotating member 27 rotates due to the motor 28. The outer surface of the rotating member 27 may be provided with ridges, pins, protrusions, etc. instead of grooves.

The first valve 21 is provided between the first extruder 11 and the resin supply port 34 of the mold 20, and can be switched between a state in which the first valve 21 and the mold 20 are in communication with each other and a state in which the first valve 21 and the mold 20 are blocked. The second valve 22 is provided between the second extruder 12 and the resin supply port 35 of the mold 20, and can be switched between a state in which the second valve 22 and the mold 20 are in communication with each other and a state in which the second valve 22 and the mold 20 are blocked. Motors 23 and 24 are attached to the valve bodies of the first valve 21 and the second valve 22, respectively, and the flow paths from the corresponding extruders to the mold 20 are opened and closed by the rotation of the motors 23 and 24.

The rotation of the motor 23 of the first valve 21, the motor 24 of the second valve 22, and the motor 28 of the kneading mechanism is controlled by the control device 18.

A cylindrical sizing 30 is provided on the side wall of the vacuum tank 4 to introduce the resin tube extruded from the mixing die 13 into the vacuum tank 14. The portion of the sizing 30 that is placed in the vacuum tank 14 has numerous holes (not shown). Since the inside of the vacuum tank 14 is depressurized, the resin tube 1 is sucked in the radial direction of the sizing 30 through the holes in the sizing 30 while passing through the sizing 30. Since the resin tube 1 is pulled up in a state of being in close contact with the inner surface of the sizing 30, the outer diameter of the resin tube 1 is set to a constant dimension determined by the inner diameter of the sizing 30. In addition, the resin tube 1 is cooled by cooling water and solidified while passing through the sizing 30.

The following describes a method for manufacturing a resin tube 1 using the extrusion molding device 100 according to this embodiment.

First, the control device 18 controls the first valve 21 and the second valve 22 so that the first extruder 11 and the mold 20 are in communication with each other and the flow path between the second extruder 12 and the mold 20 is blocked, resulting in a first state. The state control of the first valve 21 and the second valve 22 is performed by the control device 18 rotating the motors 23 and 24 to adjust the positions of the valve bodies of the first valve 21 and the second valve 22. With the first valve 21 and the second valve 22 in the first state, the first resin is extruded from the first extruder 11, thereby forming a low flexibility tube section made of the first resin.

Next, the control device 18 controls the first valve 21 and the second valve 22 to change from the first state to a second state in which at least the second extruder 12 and the die 20 are in communication with each other. In the second state, the first extruder 11 and the die 20 may be disconnected or in communication with each other.

When the second resin is extruded from the second extruder 12 in a state where the second valve 22 and the mold 20 are in communication and the first valve 21 and the mold 20 are in communication (hereinafter referred to as "second state A"), the first resin and the second resin remaining in the flow path of the mold 20 are mixed by the kneading mechanism. When the first resin and the second resin are extruded from the first extruder 11 and the second extruder 12 in a state where the second valve 22 and the mold 20 are in communication and the first valve 21 and the mold 20 are in communication (hereinafter referred to as "second state B"), the first resin remaining in the flow path of the mold 20 is mixed with the newly supplied first resin and second resin by the kneading mechanism. Immediately after switching from the first state to the second state A or the second state B, the first resin remaining in the flow path of the mold 20 is pushed out from the mold 20, and then a mixture of the first resin and the second resin, which is more flexible, is pushed out from the mold 20. By pushing out the mixture of the first resin and the second resin from the mold 20, a flexible tube section that has a lower bending rigidity and bendability than the low-flexibility tube section is formed.

In addition, in the second state B, since the first extruder 11 and the mold 20 are in communication with each other, the increase in the proportion of the second resin in the mold 20 is gradual. In the second state B, the supply amounts of the first resin and the second resin may be adjusted by the opening degree of the first valve 21 and the second valve 22.

Next, the control device 18 controls the first valve 21 and the second valve 22 to change from the second state to the first state. Immediately after switching from the second state to the first state, the mixture of the first resin and the second resin or the second resin remaining in the flow path of the mold 20 is pushed out of the mold 20, and then the resin in the flow path of the mold 20 is replaced with the first resin, and a less flexible tube section with a higher bending rigidity than the flexible tube section is formed.

The extrusion molding time in the first state and the extrusion molding time in the second state can be set according to the extrusion speed of the first extruder 11, the extrusion speed of the second extruder 12, the take-up speed by the take-up machine 16, the volume of the flow path of the mold 20, the length of the less flexible tube section and the flexible tube section to be molded, the properties of the resin such as fluidity, etc.

When multiple flexible tube sections are provided in one resin tube 1, as shown in FIG. 1, the control device 18 switches the first valve 21 and the second valve 22 from the first state to the second state, and then switches them from the second state to the first state, repeatedly multiple times (as many times as the number of flexible tube sections).

As described above, according to the extrusion molding device 100 of this embodiment, a resin tube 1 partially provided with flexible tube sections having flexibility can be molded by controlling the valves of the extrusion molding device. Even if the number, position, and length of the flexible tube sections change, there is no need to change the mold, as is the case when a bellows-shaped bend is provided using a conventional corrugator, so the resin tube 1 can be manufactured more efficiently and at lower cost than in the past.

In addition, the resin tube 1 manufactured using the extrusion molding device 100 according to this embodiment has a constant outer diameter and a circular cross-sectional shape, and therefore does not have surface irregularities such as bellows-shaped bends, making it possible to reduce the space required for piping. In addition, since there are no surface irregularities, handling is also good.

In the above embodiment, the kneading mechanism is configured using the rotating member 27 that constitutes part of the inner mold, and the supplied resin is extruded while being kneaded, but the kneading mechanism and the mold may be provided separately. For example, the kneading mechanism may be provided between the mold and the first and second valves. However, using part of the mold to configure the kneading mechanism, as in the above embodiment, is preferable because it reduces the volume of the resin flow path in the mold (remaining amount of resin) and allows the formation of a short flexible tube section.

The present invention can be used as a manufacturing device for plastic tubes used in vehicle fuel pipes, exterior materials for wire harnesses, and pipes for hot water supply equipment, etc.

Reference Signs List 1 Resin tubes 2a to 2d Flexible tube sections 3a to 3e Less flexible tube section 11 First extruder 12 Second extruder 18 Control device 20 Mold 21 First valve 22 Second valve 25 Case 26 Tubular member 27 Rotating member 100 Extrusion molding device

Claims (7)

An extrusion molding apparatus for molding a resin tube having a relatively low bending rigidity and a plurality of flexible tube portions each having flexibility,
a die for extruding the supplied molten resin into a tubular shape;
a first extruder for extruding a first resin;
a second extruder for extruding a second resin which is softer than the first resin;
a first valve provided between the first extruder and the die;
a second valve provided between the second extruder and the die;
a control device capable of controlling the first valve and the second valve in a first state in which the first extruder and the die are in communication with each other and the second extruder and the die are blocked, and in a second state in which at least the second extruder and the die are in communication with each other;
The control device forms the multiple flexible tube sections in a single resin tube by switching the first valve and the second valve from the first state to the second state, and then switching them from the second state to the first state multiple times during extrusion molding of the single resin tube . The resin tube extrusion molding device according to claim 1, wherein a kneading mechanism for kneading the supplied molten resin is provided inside the die. The extrusion molding apparatus according to claim 1 or 2 , wherein the control device controls the first valve so that communication between the first extruder and the die is blocked in the second state. The extrusion molding apparatus according to claim 1 or 2 , wherein the control device controls the first valve so that the first extruder and the die are in communication with each other in the second state. a flexible tube portion having a relatively low bending rigidity and flexibility is partially provided;
The cross-sectional shape in a direction perpendicular to the longitudinal direction is circular,
The outer diameter is constant,
A resin tube having a plurality of the flexible tube portions . The resin tube according to claim 5 , wherein the flexible tube portion is made of a resin that is softer than a first resin that constitutes the portion other than the flexible tube portion. The resin tube according to claim 6 , wherein the flexible tube portion is made of a mixture of the first resin and a second resin that is more flexible than the first resin.

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