JPS649926B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the formation of coating layers for cables, electric wires, etc.
Alternatively, the present invention relates to an extrusion method and apparatus for preventing uneven thickness used in extrusion molding of pipes, etc.

There are two types of extruder crossheads for forming coating layers for cables and electric wires: wedge ring type and fixed die type. Wedge-ring crossheads are often used for thick materials, and bolts move the die in four directions to adjust the center of the conductor and coating layer. On the other hand, fixed die types are used for thin items.
The finished outer diameter was approximately 2 mmφ at most.

The wedge ring type crosshead can be adjusted to prevent uneven thickness. However, in conventional wedge ring type crossheads, the temperature of the extruded resin such as plastic changes over time within the die, and the physical properties of the extruded resin vary greatly depending on the temperature. Even if the adjustment is correct, uneven thickness occurs during use. Because of this, adjustments had to be made many times. in this case,
As the die is moved radially, the shape of the hole also changes at the tip of the crosshead, resulting in an overall change in the flow of extruded resin within the crosshead. This had the disadvantage that it took a lot of effort and time to make adjustments, as it required repeated adjustments.

An object of the present invention is to provide an extrusion method and apparatus for preventing uneven thickness, which can easily adjust the prevention of uneven thickness.

The extrusion method for preventing uneven thickness according to the present invention uses a crosshead in which the resin flow path between the die and the nipple is eccentric except for the tip, detects the resin temperature in the circumferential direction of the resin flow path in the crosshead, and The die or the nipple is rotated so that the maximum gap between the die and the nipple is located at the point where the temperature of the resin in the circumferential direction of the resin flow path is highest.

An extrusion device for preventing uneven thickness according to the present invention includes a crosshead in which a resin flow path between a die and a nipple is eccentric except for the tip, and a temperature sensor that detects the circumferential temperature of the resin flow path, Alternatively, either one of the nipples may be rotatable around an axis.

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 to 3 show a first embodiment of the present invention. As shown in the figure, the extrusion device for preventing uneven thickness of this embodiment has a crosshead 2 connected to the tip of an extruder main body 1. crosshead 2
In the crosshead body 3, a die head 4 and a nipple 5 are fitted concentrically. The crosshead body 3 is fixed to the tip of the extruder body 1. A filament passage 6 is formed in the center of the nipple 5, through which a cable conductor or the like passes. The tip of the nipple 5 projects further forward than the tip of the die head 4. A die 7 is placed on the outer periphery of the tip of this nipple 5.
are rotatably fitted. A bushing 8 is interposed between the front end surfaces of the crosshead body 3 and the die head 4 and the rear end surface of the die 7, and allows the rotation of the die 7 while sealing between the rotating surface and the fixed surface. There is. A resin reservoir 9 is formed between the nipple 5 and the die head 4, and the space between the nipple 5 on the proximal side of the resin reservoir 9 and the die head 4 is sealed, and the surface of the nipple 5 on the distal side is filled with resin. A flow path 10 is formed. The resin reservoir 9 is connected to the resin supply path 11 of the extruder main body 1 and is adapted to receive the supply of molten resin from the extruder main body 1. A channel hole 12 formed in the die 7 to form the resin channel 10 is provided eccentrically with respect to the axis S of the crosshead 2 except for the tip of the die 7. When the flow passage hole 12 is provided eccentrically in this manner, the resin flow passage 10 is eccentric and the gap size thereof can be changed in the circumferential direction. At the tips of the die 7 and nipple 5, a resin flow path 10 is formed concentrically with respect to the axis S of the crosshead 2. That is, the contour circles of the flow passage hole 12 of the die 7 and the surfaces of the nipple 5 are formed concentrically at the tips of the die 7 and the nipple 5. In order to measure the circumferential temperature of the resin flow path 10, four temperature sensors 13 such as thermocouples are inserted into the die 7 at 90° intervals. The outer periphery of the base end of the die 7 is rotatably supported by a bearing 14. Teeth 15 are formed on the outer periphery of the tip end of the die 7, and a gear 16 is engaged with the teeth 15 so that the die 7 is rotated by the force of a rotational drive source such as a motor (not shown).

Next, an example of an extrusion method for preventing uneven thickness using such an extruder will be described. When the gap size of the resin flow path 10 is varied in the circumferential direction as in this embodiment, the temperature of the extruded resin becomes the highest at the minimum part of the gap as heat is generated due to flow path resistance. When the temperature rises, the viscosity of the extruded resin decreases and the fluidity of the extruded resin increases, and as a result, the thickness of the extruded layer increases in areas where the fluidity of the extruded resin is high, causing uneven thickness.
Focusing on such points, in this embodiment, the resin temperature in the circumferential direction within the resin flow path 10 is detected by the temperature sensor 13, and the resin flow path 10 is located at the location where the resin temperature is highest.
The gear 16 is turned to rotate the die 7 so that the maximum gap is reached. In this way, the flow path resistance at the point where the resin temperature is highest is reduced, heat generation of the resin is suppressed, and the resin temperature in the circumferential direction within the resin flow path 10 can be made uniform over the entire circumference. Dice 7
Even when the resin flow path 10 is rotated, the resin flow path 10 remains concentric at the tips of the die 7 and the nipple 5, so that together with a uniform resin flow, uneven thickness can be prevented.

FIG. 4 shows a second embodiment of the invention. The extrusion device for preventing uneven thickness of this embodiment has a nipple 5
The nipple 5 is rotatable relative to the die 7, etc., and teeth 17 are cut into the base end of the nipple 5, and a gear (not shown) is meshed with the teeth 17 to rotate the nipple 5. In this embodiment, the flow passage hole 12 of the die 7 is made concentric with the axis S of the crosshead 2, and instead, the contour circle of the surface of the nipple 5 is made eccentric with respect to the axis S, so that the resin flow passage 10 is made concentric with the axis S of the crosshead 2. It is designed to be an eccentric hole. A plurality of independent flights 18 are protruded from the outer periphery of the base of the nipple 7 and are brought into contact with the inner surface of the die head 4 so that the nipple 5 does not backflow toward its base as the nipple 5 rotates. In this embodiment, the crosshead main body 3 and die head 4 are formed as one piece. In other respects, the structure is similar to that of the first embodiment.

[Experiment Example 1] Polyvinyl chloride was produced at a temperature of 600 mm using an extruder body (cylinder) having an inner diameter of 150 mm and having the structure shown in the first example.
It was extruded at a ratio of Kg/H and coated with a sheath with a finished outer diameter of 90 mmφ, and the sheath wall thickness was 2 mm. The overall temperature of crosshead 2 was set at 170°C, and the temperature was adjusted using a PID control method. The maximum gap between the die and the nipple at the maximum eccentricity of the die 7 was 8 mm, and the minimum gap at the minimum eccentricity was 6 mm. The resin temperature is sampled every 1/10 seconds by the temperature sensor 13, the sampled values are processed by a computer, and the die 7 is rotated every few seconds so that the maximum gap between the die and nipple is located at the point where the resin temperature is high. This made the resin temperature uniform in the circumferential direction. As a result, it was confirmed that uneven thickness could be prevented.

[Experimental Example 2] PVC was extruded at a rate of 250 kg/H using an extruder body (cylinder) with an inner diameter of 150 mm having the structure of the second example, and a sheath coating with a finished outer diameter of 37.1 mmφ was performed. was set to 2.5mm. The overall temperature of crosshead 2 was set at 170°C, and the temperature was adjusted using a PID control method. The maximum gap between the die and the nipple at the maximum eccentricity of the nipple 5 is 8
mm, and the maximum gap at the maximum eccentric part was 6 mm. The resin temperature is sampled every 1/10 second by the temperature sensor 13, the sampled value is processed by a computer, and the nipple 5 is rotated every few seconds so that the maximum gap between the die and the nipple is located at the point where the resin temperature is high. This made the resin temperature uniform in the circumferential direction. As a result, it was confirmed that uneven thickness could be prevented.

Note that the temperature sensor 13 can also be built into the nipple 5 side.

As explained above, in the extrusion method and device for preventing uneven thickness of the present invention, a crosshead is used in which the resin flow path between the die and the nipple is eccentric except for the tip, and the circumferential direction of the resin flow path in this crosshead is The temperature is detected and the die or nipple is rotated so that the maximum gap between the die and the nipple goes to the point where the resin temperature in the circumferential direction in the resin flow path is highest, so the temperature in the circumferential direction in the resin flow path is Distribution can be made uniform. Therefore, the viscosity of the resin in the circumferential direction in the resin flow path is made uniform, and the amount of resin extruded is made uniform in the circumferential direction, so that uneven thickness can be prevented. In addition, in the present invention, since the resin flow path is not eccentric at the tip of the die or nipple, eccentricity does not occur at the tip of the resin flow path even when the die or nipple is rotated, which is very suitable for preventing uneven thickness. be.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment of an extrusion device according to the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a view taken along line BB in FIG. 1. , FIG. 4 is a longitudinal sectional view of a second embodiment of the extrusion device according to the present invention. 1...Extruder main body, 2...Crosshead, 3...
...Crosshead body, 4...Die head, 5...
Nipple, 7...Dice, 9...Resin reservoir, 10
... Resin flow path, 11 ... Resin supply path, 12 ... Channel hole, 13 ... Temperature sensor, 14 ... Bearing, 1
5...teeth, 16...gear, 17...teeth.

Claims (1)

[Claims] 1. Using a crosshead in which the resin flow path between the die and the nipple is eccentric except for the tip, detecting the resin temperature in the circumferential direction of the resin flow path in the crosshead,
An extrusion method for preventing uneven thickness, comprising rotating the die or the nipple so that the maximum gap between the die and the nipple goes to the point where the resin temperature in the circumferential direction of the resin flow path in the crosshead is highest. 2. A crosshead in which the resin flow path between the die and the nipple is eccentric except for the tip, and a temperature sensor that detects the temperature in the circumferential direction of the resin flow path, and either the die or the nipple is centered on the axis. An extrusion device for preventing uneven thickness, characterized in that it is configured to be able to rotate around the .