JPH0682427A - Pin hole detecting electrode for plastic hollow container - Google Patents

Abstract

PURPOSE:To provide a pin hole detecting electrode which can detect a pin hole generated during molding of a plastic hollow container such as a plastic bottle in an instant so as to shorten the inspection time and dose not damage the inside face of a container opening and leave no bristle of a metallic brush inside the container after inspection. CONSTITUTION:An internal electrode 3, which is inserted into a container for use so as to face an external electrode 2, which is arranged around the outer circumference of a plastic hollow container 1, with a container wall interposed between the internal electrode 3 and the external electrode 2, is formed from a conductive rubber into a conductive bag body having a bag part 31 according to the size of the container 1 to be inspected, so as to be passable through a neck part 13 of the container 1 to be inspected in a normal state and so as to enable to stick to the inside face of the hollow container 1 expanding by blowing with pressurized air. High voltage can be applied between the internal electrode 3 and the external electrode 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a blow molding of a laminated sheet of thermoplastics or a cylindrical film.
The present invention relates to a pinhole detection electrode for detecting a pinhole generated at the time of molding a hollow container having a neck portion that is manufactured by molding by using high voltage discharge.

[0002]

2. Description of the Related Art Conventionally, two sheets of plastic are put together in a mold and heated, and air is blown into the mold to inflate it, or a soft plastic pipe from an extruder is inserted into a mold and aired in the same manner. Although plastic hollow containers such as plastic bottles and PET bottles are manufactured by blowing in and molding, pinholes are easily generated in the parting line during molding, which is a cause of defective products. In order to detect and eliminate this before it becomes a product, most of them use an air leak checker to blow air into this kind of container for pinhole inspection, and there is also an inspection method using water. Recently, a part of a device which detects a discharge generated when a high voltage is applied across a container wall to detect a pinhole has been used.

[0003]

In the method of inspecting pinholes by blowing air into the hollow container as described above, there is a drawback that the inspection takes time because the pressure drop at the time of blowing air is detected. It takes a long time and the post-treatment is inconvenient, and in the case of using high voltage discharge, a cylindrical brush made of a thin metal wire is used as an electrode inside the container because it passes through the neck of the hollow container, but the container becomes narrower. It was unavoidable that the inner surface of the door was easily scratched at the entrance and exit, and the bristles of the metal brush fell off and remained inside the container.

The present invention has been made in view of the above points, and pinholes can be detected instantaneously, the inspection time can be shortened, and the inner surface of the container entrance / exit (neck) is damaged. It is an object of the present invention to provide a pinhole detection electrode to be inserted into and used in a plastic hollow container that does not cause unnecessary accidents such as bristles of a metal brush remaining in the container.

[0005]

To achieve the above object, in the present invention, a pinhole of a hollow container formed by molding a thermoplastic is used as an electrode for detecting using high voltage discharge. , This is composed of an external electrode that surrounds the outside of the hollow container and an internal electrode that is inserted into the container so as to face the container wall with the external electrode interposed between the external electrode and the internal electrode. In this state, the conductive rubber can be passed through the neck of the hollow container, and can be expanded by the injection of pressurized air to be in close contact with the inner surface of the hollow container. Conductive ru
bber) to form a conductive bag and to apply a high voltage between it and an external electrode.

When forming the above-mentioned internal electrodes, an internal air pipe formed of a hard pipe made of metal or hard plastic from the base, which is the air blowing port, of the conductive bag formed of the conductive rubber of the electrode to the vicinity of the tip. May be internally provided so as to be in close contact with the inner surface of the base portion of the bag body to form an internal electrode.

Further, when forming a conductive bag, it is effective to reduce the thickness of the end of the bag for the reason described below.

Further, when a concave portion or a protrusion portion is provided on the surface of the conductive bag body from the tip to the base portion to blow air into the bag body, the conductive bag body is brought into close contact with the inner surface of the hollow container. It is desirable to create an air vent at.

[0009]

When the internal electrode for detecting a pinhole constructed as described above is inserted into the hollow container made of plastic so as to face the external electrode surrounding the outside of the hollow container, the internal electrode is inserted. Since it is formed so that it can pass through the neck of the hollow container in a normal state, it can be inserted into the container without any problem, and it can be inflated by the injection of pressurized air to be intimately contacted with the inner surface of the hollow container. Since the conductive bag is made of conductive rubber according to the size of the container,
The internal electrode, which has the elasticity of the conductive rubber and an appropriate size corresponding to the size of the container to be inspected, expands due to the pressure of pressurized air and expands along the inner surface of the container (however, the corners of the bottom surface may slightly float from the inner surface). However, it is in close contact with almost the entire inner surface of the hollow part of the container.

When a high voltage is applied between the input side of the internal electrode closely attached to the inner surface of the container and the external electrode surrounding the outside of the hollow container, the conductive rubber forming the internal electrode is made of natural rubber or chloroprene rubber (synthetic rubber). Since it is formed by mixing conductive fine powder such as carbon black and has conductivity even when expanded, a high voltage is applied to the entire peripheral surface including the bottom surface across the wall surface of the hollow container. At this time, if there is a pinhole generated during processing on the parting line of the container wall or the like, since the container peripheral wall is made of plastic and is an insulator (dielectric), a high voltage is applied to both ends of the hole and this pinhole is applied. A discharge is generated through. The occurrence of this discharge can be detected and displayed by a predetermined detection device to detect the pinholes in the hollow container under test.

If an internal air pipe made of a hard pipe is installed from the air blowing port at the base of the conductive bag body to near the tip of the bag body, when the internal electrode is inserted into the hollow container, the air pipe becomes the bag body. It serves as a pillar to prevent bending of the soft bag body, facilitates insertion, and easily pulls out the internal electrode after detecting a pinhole (after removing pressurized air). When the internal air supply pipe is made of metal, it is possible to apply a high voltage to the internal electrode by applying a high voltage.

Further, if the thickness of the tip side of the conductive bag is reduced, the tip of the thin bag is expanded when the bag is inflated by being blown with pressurized air and brought into close contact with the inner surface of the hollow container. The side swells faster to facilitate elimination (easy removal) of air in the hollow container, and the conductive bag forming the internal electrode can be smoothly attached to the inner surface of the hollow container.

Further, by forming a recess or protrusion on the surface of the conductive bag body from the front end to the base portion in the form of a stripe or in the form of irregularities on the entire surface (wart-like shape), the bag body swells and becomes hollow. When it comes into close contact with the inner surface of the container, an air passage, that is, an air vent, can be easily formed between the inner surface and the inner surface.

[0014]

Embodiments of the pinhole detecting electrode of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a principle diagram for inspecting a pinhole of a plastic hollow container 1 having a screw on the outer circumference of the neck of the container inlet / outlet using the pinhole detection electrode of the present invention. The plastic hollow container 1 is formed by stacking two sheets of thermoplastics such as polyethylene and heating them by sandwiching them in a mold to blow air into the mold to inflate it or molding a tubular container from an extruder into a mold. The container is a hollow container having a circular cross section and having a neck portion formed by blowing air into the container. In some of these hollow containers, pinholes are often generated on the parting line during manufacturing. Of the electrodes facing each other to detect this pinhole, the external electrode 2 located outside the container across the container wall is
A pair of side electrodes 2 ₁ surrounding the neck 1 ₃ and a cylindrical side wall 1 ₁ of the hollow container 1 from the left and right sides in close contact, 2 _1, container bottom 1 ₂
A hollow container 1 consisting of a bottom electrode 2 ₂ for close contact with
Is provided so that it can be exchangeably surrounded.

[0016] On the other hand, the internal electrode 3 to be inserted using the hollow container 1, using a conductive rubber (Conductive rubber), normally to be passed through the neck portion 1 ₃ of the hollow container 1 (pre-insertion state),
Moreover, the hollow container 1 is expanded by blowing pressurized air.
Bag unit corresponding to the dimensions of the hollow container 1 to be inspected of the inner surface so as to be in close contact 3 ₁ and the conductive tube 4 for energizing the DC high voltage
The formed conductive bag body as having a blow port 3 ₃ provided with a ring-shaped protrusion around in order to mount the base portion 3 ₂ and the external air supply pipe 5 to be fitted, the base of the bag body 3 ₂ a conductive tube 4 is mounted, so that it applies a high voltage of direct current allowed coupling conductors 4 ₃ from outside. Further, the conductive tube 4 and the bag body base 3 ₂ insulating cap 4 ₁ across the front is covered, from the air tube 5 attached to the blow port 3 ₃ by inserting the internal electrode 3 to the hollow container 1 pressurized air 7 inflated a blow bag unit 3 ₁ in close contact to the hollow container 1 interior surface, when the high DC voltage is applied to the internal electrode 3 from conductor 4 _3, bladder base of the internal electrode 3 3 ₂ An unnecessary discharge is prevented from occurring between the external electrode 2 and the upper part of the external electrode 2.

The bag portion 3 _{1 of} the conductive bag body forming the internal electrode 3
On the surface of the air in the container 1 when allowed to contact the electrode 3 a hollow container 1 by inserting the bag portion 3 ₁ blowing pressurized air expansion allowed by the bag portion 3 ₁ of the surface to the inner surface of the container The air vent groove 3 ₁ 'from the top of the bag 3 _{1 to} the base 3
Toward ₂ forward are symmetrically formed on the striations form a side surface of the bag portion 3 ₁ (see FIG. 2: In addition in the state grooves opposite the hidden in the drawing). Thus, the container sidewall 1 ₁ bag portion 3 ₁ expands
Initially, the groove 3 ₁ ′ comes into partial contact and close contact with the inner surface initially, but when the contact and close contact gradually spreads and completely adheres to the inner wall of the hollow portion of the container, the groove 3 ₁ ′ has side walls 1 ₁ and bottom 1 ₂ can form a vent, smooth the air to eliminate the surface of the bag portion 3 ₁ of the container can be allowed to contact the inner surface of the container between.

Further, the conductive bag air blowing port 3 ₃ up to the base 3 ₂ inserted through near the tip of the bag portion 3 ₁ a, at a slightly spacing the tip inner surface, a metal, a hard material such as plastic An internal air supply pipe 6 having a predetermined diameter is inserted and internally mounted. A plurality of blowout small holes 6 ₂ is blown efficiently pressurized air is bored with allowed to stretch inflatable bag portion 3 ₁ to the internal feed pipe 6 is a side other than the air outlet ₆₁ of the tip, the bag part 3 ₁ acts as a strut to prevent bending, to facilitate the insertion and withdrawal of the bag portion 3 ₁ to the hollow container 1.

When inspecting the pinhole of the hollow container 1 to be inspected, the internal electrode 3 having the above-described structure is provided along the central axis of the hollow container which is localized by surrounding the outer side of the outer electrode 2.
The, for example, the internal electrodes base of the insulating cap 4 ₁ insertion-drawing means (not shown) was allowed to hold the barrel or the like, and as allowed insertion orientation the tip of the bag portion 3 ₁ of the electrode is close to the bottom surface of the hollow container 1 After that, the air tube 5 connected to the internal electrode 3
More pressurized air 7 air to the internal electrode 3, and stops the air in contact allowed by a pressurized state into the hollow inner surface of the test container 1 inflated the bag portion 3 ₁ consisting of the conductive rubber. Then the high-voltage internal electrodes 3 (plus side) than the conductive tube 4 via a line 4 ₃
Is transmitted to both the inner and outer electrodes 3, 2 and an appropriate high DC voltage between 10KV and 30KV, which corresponds to the thickness and material of the container to be tested,
It is applied from a high-voltage power supply unit of a pinhole detector (not shown). Side walls 1 ₁ of the test hollow container 1 by applying a high voltage,
Bottom 1 ₂ and the container shoulder, neck 1 ₃ of the base of the narrowed there is a pinhole in the neck like an arc between the inner and outer electrodes 3,2 (discharge) is generated, the discharge the pinhole detector Is displayed on the display lamp or is output as an alarm.

When the detection of the pinhole is completed, the application of the high voltage to both the inner and outer electrodes 3 and 2 is stopped, and the pressurized air pressure-fed to the inner electrode 3 is fed to the air feeding pipe 5 in the middle of the piping (not shown). to exhaust pressurized air by opening the valve provided after deflated bag portion 3 ₁ of the internal electrode 3 to the original normal state, pull out the internal electrode 3 in the insertion and pull-out means. In addition, the external electrode 2 is opened to release the container to be inspected, and the container is taken out to prepare for the next inspection of the container to be inspected. By inspecting the plastic hollow container in this way, it is possible to detect pinholes instantaneously and shorten the inspection time, as well as scratching the inner surface of the neck of the hollow container to be inspected and It is possible to completely prevent unnecessary matters such as bristles of a metal brush from remaining in the hollow container and causing an accident.

At the time of manufacturing the internal electrode 3, instead of the air vent groove 3 ₁ ′, the side wall portion of the bag portion 3 ₁ is divided into two parts to be joined to form a bag body, and the seam is formed. Bag
It is possible to form an air bleeding ridge 3 ₁ "by projecting linearly from the tip of 3 _{1 to} the front of the base 3 ₂ on the side surface of the bag 3 ₁ (see FIG. 3). 3 ₁ of the surface can form a vent can narrow air passages at the contact portion between the projecting strip 3 ₁ "and the inner surface of the container when going sequentially close contact with the hollow inner surface of the container. Further, instead of the air vent may be provided Iboibo shape ridge portions throughout the bag portion 3 ₁ surface.

Further, by reducing the thickness of the bag portion 3 ₁ of the distal end side, air on the distal end side hollow container 1 when the bulge earlier is likely to exclude (easy missing), the conductive bag adhesion to the hollow container inner surface of the bag portion 3 ₁ becomes easier, may be used in place of the air vent grooves or ridges, but with thinner distal end side of the bag portion 3 _1, grooves or butt for the air vent It is even more effective when used together.

In the above embodiment, the hollow container 1 for the internal electrode 3 is used.
In order to make it easy to put in and out, the hard internal air supply pipe 6 is installed, but instead of this, a metal ball such as a pachinko ball is placed in the conductive bag body and the pulling force is applied to the conductive bag body. May be added so that the internal electrode 3 can be easily put in and taken out of the hollow container 1. Further, in the above embodiment, the pinhole detection electrode of the plastic hollow container having a circular container cross section is described, but the conductive bag body forming the internal electrode is formed in a free shape corresponding to the shape of the container. Because you can
For example, it is possible to form an electrode for pinhole detection of a hollow container with a special cross-sectional shape whose square cross-section is close to square or rectangular. It can also be used for hole detection, and various modifications can be made without departing from the scope of the present invention.

[0024]

According to the pinhole detection electrode of the present invention as set forth in claim 1, pinholes generated during molding of hollow containers such as plastic bottles and PET bottles manufactured by blow molding of thermoplastics. When detecting air pressure, it is possible to eliminate the shortcomings of the time-consuming inspection method that was previously used by injecting air and detecting the pressure drop at that time, and to instantly detect pinholes and shorten the inspection time. it can. In addition, the method of inspecting with a high voltage by inserting a metal cylindrical brush in a part of the hollow container is easy to scratch the inner surface of the inlet / outlet (neck) of the hollow container, and after the inspection, it is often inside the container. Although there were serious drawbacks that metal bristles remained and caused accidents, all of these drawbacks were resolved to prevent scratches on the inner surface of the entrance and exit of the hollow container, and the metal inside the container after inspection. It is possible to provide an electrode for pinhole detection that is easy to inspect and completely has no brush hair left.

According to the second aspect of the present invention, when the internal electrode of the pinhole detecting electrode is used by inserting it into the hollow container to be inspected, the internal rigid hard air supply pipe prevents bending of the electrode. The insertion can be facilitated and the electrode can be easily withdrawn after the inspection is completed.

According to the third aspect of the present invention, when the internal electrode is inserted into the hollow container to be inspected and air is blown to inflate the conductive bag body of the electrode to bring it into close contact with the inner surface of the inspected container, By making the thin bag body bulge from the container bottom side on the tip side, it is possible to easily remove the air from the container to be inspected and to bring them into close contact with each other smoothly.

According to the invention of claim 4, when the conductive bag body of the internal electrode swells and adheres closely to the inner surface of the hollow container, an air passage, that is, an air passage, is formed between the surface of the conductive bag body of the electrode and the inner surface of the hollow container. Air can be easily formed, and the inner electrode and the inner surface of the hollow container can be easily brought into close contact with each other.

[Brief description of drawings]

FIG. 1 is a principle diagram when inspecting a pinhole of a plastic hollow container using the pinhole detection electrode of the present invention,

2 is an external side view of the internal electrode for detecting the pinhole shown in FIG. 1,

FIG. 3 is an external side view of another internal electrode for pinhole detection.

[Explanation of symbols]

1 ... Hollow container, 1 ₁ ... Side wall, 1 ₂ ... Bottom part, 1 ₃ ... Neck part,
2 ... External electrode, 3 ... Internal electrode, 3 ₁ ... Bag, 3 ₁ '... Air vent groove, 3 ₁ "... Air vent ridge, 3 ₂ ... Base, 4 ...
Conductive cylinder, 4 ₁ ... Insulation cap, 4 ₃ ... Conductive wire, 5 ... Air supply pipe, 6 ... Internal air supply pipe, 7 ... Pressurized air.

Claims (4)

[Claims] 1. An electrode for detecting a pinhole of a hollow container formed by molding a thermoplastic using high-voltage discharge, comprising an external electrode surrounding the outside of the hollow container and a container wall. The inner surface of the hollow container is composed of an internal electrode which is inserted into the container so as to be opposed to each other so as to be able to pass through the neck of the hollow container in a normal state and is expanded by blowing pressurized air. The pin of the plastic hollow container is characterized in that the conductive bag is made of a conductive rubber corresponding to the size of the container to be inspected so that it can be closely adhered to the conductive bag, and a high voltage can be applied to the external electrode. Electrode for hole detection. 2. The internal electrode is formed from the base of the conductive bag body to the vicinity of the tip so that an internal air supply pipe made of a hard pipe is provided so as to be in close contact with the inner surface of the bag base so as to form an internal electrode. Electrodes for detecting pinholes in plastic hollow containers. 3. The pinhole detection electrode for a plastic hollow container according to claim 1 or 2, wherein the thickness of the end of the conductive bag is thin. 4. A recess or a protrusion is provided on the surface of the conductive bag body from the front end to the base part to form an air vent when the conductive bag body is brought into close contact with the inner surface of the container by blowing air. The pinhole detection electrode of the plastic hollow container according to claim 1, 2 or 3.