JPH0146023B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for inspecting thin-walled plastic molded containers that house various foods and are used disposablely.

Due to recent rationalization of distribution and sales systems, food items are often sold by weighing them into thin-walled plastic containers. The plastic containers used here are made of thermoplastic sheets and are molded to be as thin as possible to reduce the amount of materials used, reduce wasted resources due to disposable containers, and reduce manufacturing costs through mass production. By the way, when mass producing this kind of thin-walled plastic containers,
When screening defective products during the manufacturing process, it is easy to identify defects based on their external appearance, but it is extremely difficult to detect pinholes, which are considered serious defects in containers, and appropriate inspection methods are required. The current situation is that there is no such thing.

The present invention was developed in view of the above points, and makes it possible to easily detect pinholes electrically by utilizing the insulating properties of a plastic container.

Embodiments of the present invention will be described below with reference to the drawings.

1 is an external electrode, and this electrode is provided with a recess 2 into which the container A to be inspected is loosely inserted. Reference numeral 3 denotes an internal electrode, which consists of a large number of needle-like electrodes 5 scattered on the 4 sides of an electrode housing made to match the internal shape of the container A to be tested, and when inserted into the container A to be tested, the container A slight gap is formed between each part and the needle electrode 5.

The electrode housing 4 has a gas jet hole 6 located at an appropriate location between the needle-shaped electrodes, which blows high-pressure gas toward parts of the container A to be inspected that are likely to be distorted, such as the bottom corner, bottom surface, and center of the side surface. The gas ejection hole 6 is connected to a high pressure gas source. In addition, 7 in the figure
1 is a lifting platform for both the inner and outer electrodes 1 and 3, and both electrodes 1 and 3 are moved up and down from the solid line position to the broken line position in the figure. 8
is an air hole bored in the external electrode 1.

Therefore, in order to inspect the container A to be inspected, the container A is placed on the outer electrode 1 in the lowered position with both the inner and outer electrodes 1 and 3 separated, and the upward movement of the outer electrode 1 causes the container A to is inserted into the concave cavity 2. At this time, the air existing between the concave hole 2 of the external electrode 1 and the container A flows out from the air hole 8, and the external electrode 1 is charged due to the previous application of high voltage, and this It acts to pull the two together, and the two come into perfect contact. Next, the internal electrode 3 in the raised position is moved downward to be inserted into the container A. In the process of inserting this internal electrode 3 into the container A, high-pressure gas from a high-pressure gas source is blown onto various parts of the inner surface of the container A through the ejection holes 6 of the electrode housing 4.
While correcting the local deformation of the container A, the container A is pressed into the internal position of the recess 2 of the external electrode 1. In this way, the insertion movement of the internal electrode 3 and the supply of high-pressure gas are stopped at the position where the needle-like electrode 5 and each part of the container A side face each other with a slight gap formed, and in this state, a high voltage is applied to both the inner and outer electrodes. do. This voltage caused a complete discharge between the tip of each needle-like electrode 5 of the internal electrode 3 and the corresponding surface of the external electrode 1 when the container A was not inserted between the two electrodes, and the gap was slightly widened. A voltage high enough to cause discharge is set in advance.

If there is no abnormality in container A due to the application of high voltage to the inner and outer electrodes 1 and 3, no electrical change will occur due to its electrical insulation, but if a pinhole B exists somewhere in container A, This pinhole B
The needle-like electrode 5 of the inner electrode 3 closest to and the outer electrode 1
A discharge occurs between the containers, and from this, defective containers can be immediately identified and eliminated.

In addition, even in the process of extracting the internal electrode 3 from the container A after inspection, high-pressure gas is blown from the electrode housing 4, which may cause problems such as the container A floating up naturally and coming into contact with the needle electrode 5, causing damage. Make sure not to.

That is, according to the present invention, a defective container is identified by inserting the container to be inspected between the inner and outer electrodes and applying a high voltage between both electrodes, which is much easier to detect than visual inspection by human eyes. In order to improve efficiency, this test involves inserting a number of needle-shaped electrodes into the container and bringing them very close to the inner surface of the container, and during the electrode insertion process, high-pressure gas was blown against the inner surface of the container. Therefore, even if there is a local deformation of the container, this is corrected during the inspection, and the container is held in place so that it does not come into contact with the internal electrode, thus preventing damage due to contact with the needle electrode. However, inspection can be carried out reliably and quickly, and its usefulness is extremely large in terms of mass production of thin-walled plastic containers.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a configuration diagram, FIG. 2 is an explanatory diagram of a discharge state, and FIG. 3 is an explanatory diagram of a gas blowing state. DESCRIPTION OF SYMBOLS 1... External electrode, 2... Recess, 3... Internal electrode, 4... Electrode housing, 5... Needle electrode, 6... Gas ejection hole, 7... Lifting platform, 8... Air hole.

Claims (1)

[Claims] 1. Insert the container to be tested into the concave cavity formed in the external electrode, and in the process of inserting the internal electrode, which is made up of a number of needle electrodes implanted on the surface of the electrode housing similar to the shape of the container, into the container. Blow high-pressure gas from the housing to press the container to be inspected toward the external electrode, form a slight gap with each part of the surface of the container to be inspected, and place the needle-like electrodes facing each other, stopping the insertion movement of the inner electrode housing and the gas supply. After that, a high voltage was applied to both the inner and outer electrodes, and if there was a pinhole in the container to be inspected, a discharge was generated between the needle electrode closest to the pinhole and the outer electrode through the pinhole. A plastic container inspection method characterized by: