JPH08323841A - Foreign matter inspection device for plastic extruder - Google Patents

Abstract

PURPOSE: To certainly inspect foreign matter by inspecting the total amt. of foreign matter of a plastic insulating material subjected to the coating of a power cable by a crosshead immediately before extruding the plastic insulating material to coat a conductor. CONSTITUTION: In an apparatus for inspecting foreign matter in plastic extruded from a plastic extruder, a glass light pervious part 9 for observing the plastic passage 8 in the adaptor 6 provided to the leading end of the plastic extruder is provided to the adaptor 6 and a light source, a scanner or lens for repeatedly scanning the parallel light from the light source in the plastic passage 8 and a light detector arranged at the position outside a light path are arranged outside the light pervious part. The plastic flowing through the plastic passage 8 is irradiated with the parallel light from the light source and the scattered light from the foreign matter in plastic is detected by the light detector to inspect the foreign matter in the plastic flowing through the passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign substance inspection apparatus for inspecting the total amount of plastic extruded from a plastic extruder for the presence of foreign substances.

[0002]

BACKGROUND OF THE INVENTION Plastic-insulated power cables are manufactured by a method in which pellet-shaped insulating material is melted by a plastic extruder and extruded to coat the conductor surface. In the power cable manufactured in this way, the long-term reliability improvement of the plastic insulator is strictly required in accordance with the high-voltage power cable, and the plastic that is considered to cause the dielectric breakdown in particular. It is necessary to strictly control and manufacture foreign substances in the insulator.

In the conventional foreign matter inspection, a method of inspecting a pelletized plastic material before being put into a plastic extruder or a method of taking out a part of plastic extruded from the plastic extruder into a sheet shape and inspecting it is adopted. It was

By the way, in the method of inspecting the pellet-shaped plastic material before being put into the plastic extruder,
Not all foreign materials generated inside the plastic extruder can be guaranteed. Further, in the sampling inspection method in which a part of the plastic extruded from the plastic extruder is taken out into a sheet shape and inspected, this is also very similar in relation to the presence or absence of foreign matter in the plastic actually coated on the power cable. There was a problem that it was unclear and could only make ambiguous decisions.

Therefore, a rectangular light-transmitting portion is formed in the adapter portion of the plastic extruder, and laser light from a laser light source is made incident on this light-transmitting portion so as to scan the plastic light passing through the flow path in the adapter. There has been proposed a method of detecting and inspecting a shadow caused by a foreign substance in plastic by a light receiver which is transmitted and is arranged at a position in an optical path facing the incident side. (See Japanese Patent Laid-Open No. 3-284927) In the case of the method of inspecting by transmitting the laser beam, it is an excellent inspection method capable of inspecting the entire amount of plastic to be coated from the plastic extruder, but the laser beam wavelength Since it is necessary to reduce the width of the plastic flow path in the light-transmitting part in order to accurately detect foreign matter in the plastic from the relationship between the depth of focus and the depth of focus, gradually change the flow path cross-sectional shape from circular to rectangular. Had to be formed. This is because it costs a lot of money to manufacture the adapter, and because the shape of the flow path is not constant, scorch is likely to occur on the wall surface of the light transmitting part due to the change in the flow velocity of the plastic flowing in the flow path, and the foreign matter There were problems such as the inability to judge the three-dimensional size.

The present invention has been made in view of the above points, and a total amount of foreign matter in the plastic insulator actually used for coating the power cable is inspected immediately before the conductor is extrusion coated by the crosshead. An object is to provide an inspection method capable of surely inspecting foreign matter.

[0007]

DISCLOSURE OF THE INVENTION The present invention is intended for observing a plastic flow path inside an adapter in an adapter provided at the tip of the plastic extruder in a foreign matter inspection device in plastic extruded from a plastic extruder. A glass light-transmitting portion is provided, a parallel light source on the outside of the light-transmitting portion, a scanning device for repeatedly scanning light rays from the light source into the plastic flow path, and a light receiver installed outside the light path. , And irradiate the plastic flowing in the plastic flow path with a light beam from the light source so that the scattered light scattered from the foreign matter in the plastic is received by the above-mentioned light receiver to remove the foreign matter in the plastic flowing in the flow path. It is a foreign material inspection device for a plastic extruder that is inspected. Further, it is a foreign matter inspection device for a plastic extruder in which the cross-sectional shape of the plastic flow passage of the glass translucent portion is a circle having the same diameter as the flow passage cross-sectional shape of the adapter portion.

[0008]

[Function] The presence / absence of foreign matter is detected by shining parallel light on plastic flowing in a plastic channel having a constant cross-section and detecting scattered light generated when the parallel light hits the foreign matter by a light receiver provided outside the optical path. It is possible to reliably inspect the entire amount of plastic.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an adapter attached to a plastic extruder. That is, the adapter 6 is the cylinder 1 into which the screw 2 of the plastic extruder body 3 is inserted.
Is disposed at the end of the. An adapter 6 having a plastic flow path 8 formed therein is connected to the tip of the cylinder 1 with the crosshead 7. A breaker plate 4 and a screen 5 are arranged and fixed in the plastic flow path of the connecting portion between the cylinder 1 and the adapter 6. Therefore, the rotation of the screw 2 melts the plastic material and pushes it toward the breaker plate 4. On the screw 2 side of the breaker plate 4, a screen 5 for removing foreign matters in the plastic material is arranged. The plastic material passing through the breaker plate 4 flows through the plastic flow path 8 in the adapter 6 and is covered by the crosshead 7 on the surface of the cable conductor (not shown).

The adapter 6 has a cylindrical glass translucent portion 9 having a plastic flow path 8 having a circular cross section between the left and right adapter bodies 6a and 6b, and a bolt 16 is screwed into the adapter 6. Are formed integrally with each other. The translucent part 9 can transmit light to the plastic passing through the central plastic flow path 8 to illuminate it. Further, when the foreign matter 14 exists in the plastic, the illumination light is reflected by the foreign matter, and the reflected light can be transmitted through the transparent portion 9 and detected from the outside.

FIG. 2 shows an outline of an optical system for detecting foreign matter. That is, the laser light 13 from the laser light source 10 is scanned by a scanning device such as a polygon mirror 11 that rotates at a high speed, converted into parallel light by a lens 12, and then transmitted through a light transmitting portion 9 in the adapter 6 to flow through a plastic stream. The irradiation is performed so that only the width of the path 8 is scanned. Therefore, the parallel laser light 13
Irradiates the plastic flowing in the plastic flow path 8 while being refracted by the light-transmitting part 9 made of glass. Then, the light passes through the plastic and is emitted to the optical path a on the opposite side via the light transmitting portion 9 made of glass.

If there is a foreign substance 14 in the plastic flowing through the plastic flow path 8, the irradiated laser light is scattered, and this scattered light passes through the light transmitting portion 9 made of glass and is outside the optical path a in the direction perpendicular to the flow path 8. CCD camera placed in position,
The light is made incident on the light receiver 15 including an image sensor such as a vidicon and an optical sensor such as a photomultiplier tube. By detecting the reflected light from the foreign matter 14 in this manner, the foreign matter can be detected with high sensitivity. At this time, by disposing another optical receiver on the opposite side of the adapter 6, the sensitivity of foreign matter detection can be further increased, and the reliability can be improved.

Still another embodiment will be described with reference to FIG. In this case, the light receivers 15a, 15b, 15c and 1
By installing 5d outside the optical path a of the illuminating light by 90 degrees out of phase, the scattered light from the foreign matter 14 is combined with two light receivers such as the light receivers 15a and 15b and the light receivers 15a and 15c. It is possible to capture it stereoscopically. In this case, it is possible to judge the approximate size of the foreign matter based on the intensity of the scattered light from each light receiver. Since the scanning of the laser light is sufficiently faster than the flow velocity of the plastic material flowing in the plastic flow path 8, the length of the foreign matter in the flow direction can be determined by integrating the intensity of the scattered light.

In the above-mentioned embodiment, the light receiver is arranged in the same plane as the optical axis of the illumination light, but as shown in the perspective view of FIG. The photodetector 15 is shifted by 90 degrees at a diagonally lower position or an obliquely upper position that does not overlap with the plane including the optical axis of the illumination light at a right angle.
It is also possible to dispose and detect e and 15f. These light receivers receive scattered light from a foreign material of a plastic material that passes through the plastic flow path 8 of the light transmitting portion 9 and photoelectrically convert it, and process the signal by a signal processing circuit to perform data processing or alarm. Is configured to emit.

Further, in the above-mentioned embodiment, the case where the irradiation light is a spot light source of laser light has been described. However, this is also applicable when visible light from a light source such as a halogen lamp is collimated by a lens and illuminated. Good. In this case, if a light receiver such as a CCD camera, an image sensor such as a vidicon, and a light receiver such as a photomultiplier tube are combined as the light receiver, a highly sensitive inspection can be performed. Therefore, in this case, a scanning tool such as a polygon mirror for scanning the width of the plastic flow path in the optical path is unnecessary.

[0015]

As described above, according to the foreign matter inspection device for a plastic extruder of the present invention, the optimum cross-section is circular without adopting a method of gradually changing the plastic flow path of the light transmitting part of the adapter into a rectangular shape. It is possible to form the light-transmitting portion for detecting foreign matter while maintaining the flow path shape. In the method of detecting the shadow of a foreign substance by a transmission laser beam, the width of the depth of focus is small, and it becomes difficult to detect the foreign substance due to defocusing.Therefore, the light-transmitting part must have a rectangular elongated shape. There wasn't. Therefore, in this case, the plastic flow velocity distribution in the flow path becomes extremely uneven, and scorch of the plastic material may occur in the low flow velocity portion near the wall surface of the light transmitting portion. In addition, the light receiver can be installed only on the opposite side to the laser light incident side, so even if a rectangular elongated translucent part is provided to clarify the size of the foreign matter, the projection of the foreign matter from one direction It was impossible to judge the size of the depth of the foreign material because it was only possible to understand the shape. In order to judge the size, another light receiver may be added at a position where the phase is shifted by 90 degrees, but in this case, it becomes out of focus and it becomes impossible to judge the size. That is, it can be said that correct detection is impossible unless the shape of the foreign matter is spherical. On the other hand, according to the present invention, it is possible to efficiently inspect the entire amount of the plastic material that covers the presence or absence of foreign matter efficiently while ensuring the flow path shape in which the plastic material does not cause scorch.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of an adapter attached to an extruder according to an embodiment,

FIG. 2 is an optical path diagram of a foreign matter detection optical system,

FIG. 3 is an optical path diagram of a foreign matter detection optical system according to another embodiment,

FIG. 4 is a perspective view showing another arrangement example of a light receiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 cylinder 2 screw 3 extruder main body 4 breaker plate 5 screen 6 adapter 7 crosshead 8 plastic flow path 9 glass translucent part 10 laser light source 11 scanning tool 12 lens 13 laser beam 14 foreign material 15, 15a to 15f light receiver

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masami Mori 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki “Hitachi Cable Co., Ltd. Hidaka Plant”

Claims (2)

[Claims] 1. An apparatus for inspecting foreign matter in plastic extruded from a plastic extruder, wherein an adapter provided at a tip of the plastic extruder is provided with a glass translucent portion for observing a plastic flow path inside the adapter. A light source and a scanning device for repeatedly scanning parallel light rays from the light source into the plastic flow path or a lens and a light receiver installed at a position outside the optical path are arranged outside the light transmitting portion, The parallel light rays from the light source are applied to the plastic flowing through the plastic flow path, and the scattered light scattered from the foreign matter in the plastic is received by the above-mentioned light receiver,
A foreign matter inspection device for a plastic extruder, which is configured to inspect foreign matter in a plastic flowing through a flow path. 2. The foreign matter inspection device for a plastic extruder according to claim 1, wherein the cross-sectional shape of the plastic material flow passage of the glass translucent portion is a circle having the same diameter as the flow passage cross-sectional shape of the adapter portion.