JPH0623716B2 - Defect detection method and device for laminated material can lid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention uses a flaw of a laminated material can lid, particularly a metal plate as a base material,
A plastic film on the inner surface side, and a recess formed on the inner surface side by a rivet for attaching score line tearing tabs to the peripheral wall of the recessed hole of the can lid. The present invention relates to a method and apparatus for detecting the presence / absence.

[Conventional technology]

The laminated material easy opening can lid is known,
The shape is shown in FIGS. 2 and 3.

FIG. 2 shows the appearance of the outer surface of the easy opening can lid. 1 is a lid, 3 is a score line, 4 is a score line tear tab, and 5 is a rivet for tab attachment.

Fig. 3 shows A in Fig. 2 of the easy opening can lid.
-A cross-section is shown, 2 is an inner surface side, 6 is a concave hole formed by rivets, and 7 is a peripheral wall of the concave hole.

On the other hand, a method of forming a rivet for attaching a score line tearing tab is performed by repeatedly making a metal rivet several times in a step of forming a rivet and a step of fixing the tab to the rivet, as disclosed in Japanese Patent Publication No. 52-39353. The pin of is inserted into the concave hole, but if the position of this metal pin and the concave hole shifts even a little, the metal pin rubs the peripheral wall of the concave hole and the inner plastic film is scratched to expose the metal surface. Will be done.

In mass production of this can lid by the conventional method, it is unavoidable that some percentage of the can lid has a flaw in the plastic film on the peripheral wall of the recessed hole, and effective measures against this are still unknown. Has not been done.

On the other hand, a discharge type inspection method is known as a pinhole inspection method for a plastic film or a coating film, and this method is applied to an inspection of a plastic bottle or a plastic easy opening bottle lid.

Pinhole inspection for plastic bottles
It is described in Japanese Patent No. 26165. This is for the purpose of inspecting pinholes formed on the wall of the bottle 31, as shown in FIG. 7, and the inner and outer electrodes 33 and 34 having a shape along the wall of the bottle are separated from the bottle wall inside and outside the bottle. In this condition, the bottle mounting table 32 is rotated, and a voltage of 25 to 35 KV is applied between the internal electrode 33 and the external electrode 34 to detect the presence or absence of discharge between the electrodes. It is done by.

As for the inspection of the plastic easy opening bottle lid, the one shown in FIG. 8 is known. In this method, a plastic bottle lid 41 provided with a score line 42 is placed on a lower electrode 44 having a diameter substantially equal to the inner diameter of the bottle lid, and an upper electrode 43 is placed.
Is a large diameter that substantially covers the opening surrounded by the score line 42 and is opposed to the lower electrode 44.

Both electrodes do not rotate, and if there is a pinhole in the bottle lid when a high voltage is applied between both electrodes, a leak current flows between the upper and lower electrodes, and by detecting this leak current, the bottle lid's It detects flaws.

[Problems to be solved by the invention]

When the object is rotated like the above bottle inspection method, when the object is a can lid, the can lid transferred to the detection position is rotated for detection, and the rotation is stopped after the detection is completed. After this, the detection position must be moved to the next step, which is not suitable for accurately inspecting a large number of can lids in a fixed time, and has a drawback that detection efficiency becomes poor.

When the above plastic easy-opening bottle lid inspection method is applied to a can lid, the electrode becomes large with the radius from the center of the can lid to the recessed hole, and a large high voltage generator is required, resulting in cost increase. Not only will it be impossible to detect unless a very high voltage is applied,
Plastic films and organic substances of several microns to several tens of microns will be destroyed by this high voltage, and normal swelling of the film will be detected in the same manner as the flawed part, and the detection system will be extremely poor.

This invention has been made to detect a flaw in a laminated material easy opening can lid that solves the above-mentioned drawbacks.
To obtain a method and a device that can be incorporated into a can lid production line of 150 to 400 sheets / min, enable high-precision, high-efficiency, and high-speed detection processing, have a low applied voltage, and can reliably detect flawed can lids. With the goal.

The present invention can be effectively used, of course, for detecting flaws in a thin plastic film having a metal plate as a base material and having a thickness of several microns to several hundreds of microns or other products to which organic substances are attached.

[Means and Actions for Solving Problems]

The present invention intermittently transfers one by one the easy opening can lids formed with the laminated surface of the film as the inner surface with the inner surface as the upper side, and fixes the can lids transferred to the detectors by a chuck. Then, the can lid is held at a predetermined detection position while the chuck is raised and detected, and the inner surface of the can lid is kept at a predetermined distance from the inner surface of the can lid, and the central axis of the can lid is used as an axis and the recessed hole of the can lid is provided. The revolving electrode having a small electrode that revolves at a radius passing through the center of the revolving electrode is rotated, and a predetermined high voltage is applied to the revolving electrode for a minute time during which the revolving electrode revolves for two revolutions or more.

No matter which direction the recessed hole in the can lid at the detection position is facing, be sure to scan near the recessed hole while the revolution electrode rotates.
When the plastic film has a flaw, a leak current of a predetermined current or more flows between the revolution electrode and the ground electrode with which the can lid is in contact. It is possible to detect the presence of a flaw on the easy-opening can lid made of a laminated material by detecting a current equal to or higher than the predetermined value.

〔Example〕

The shape of the easy opening can lid used to detect the flaw is
It is as shown in FIGS. 2 and 3, and 8 is a part of the panel that most protrudes toward the inner surface side.

The laminated material used for the can lid is made by coating a normal epoxy paint on the outer surface with an epoxy phenolic paint on the inner surface of an aluminum plate with a thickness of 0.25 mm, and then polypropylene on the inner surface. A polypropylene film having a thickness of 30 μ is laminated with an adhesive.

Of course, the same can be detected in the case of a can lid in which the inner surface of the aluminum plate is not coated with epoxyphenol and the inner surface of the aluminum plate is directly laminated with a polypropylene film with a polypropylene adhesive.

A schematic diagram of an inspection device for flaw detection is shown in FIG.

The can lid is supplied from the automatic can lid feeder 17, and the can lid is fed from the right side to the left side intermittently at equal intervals as shown by the arrow, and progresses. However, the can lid is at the lowering position of the detector. Position (indicated by a broken line in the figure), the can lid is fixed to the chuck by vacuum suction, and then the chuck 11 moves up (the position indicated by the solid line in the figure) and the revolution electrode 14 attached to the revolution electrode holder 15 The structure of the chuck is such that the gap with the can lid 1 has a predetermined size.

Reference numeral 20 is an ejector of the can lid with the detected flaw, and 21 is a stacker of the can lid with no flaw detected. The revolution electrode 14 is used as the high voltage generator 18, and the chuck 11 is used as the leak current detector 1.
9 are connected by lead wires 16 and 13, respectively.

The can lid 1 is held at the detection position, the revolution electrode holder 15 is rotated, and a voltage is applied to the revolution electrode 14 for a minute time. Regardless of the direction of the recessed hole of the can lid at the detection position, the revolution electrode 14 always scans the vicinity of the recessed hole while rotating, and if the plastic film has a flaw, a leak current flows to the ground electrode 12. .

FIG. 6 shows a detection mechanism mainly for electrical relation.

The voltage from the high voltage generator 18 is adjusted to a predetermined voltage by the voltage setting device and applied to the revolution electrode 14, and this voltage is displayed on the voltage display.

On the other hand, the ground electrode 12 is connected to a leak current detector 19 for detecting a leak current of a predetermined value or more, and the current value thereof is adjusted by the detection current setting device. The output of the leak current detector enters the NO and GO signal generators, and controls the flaw ejector 20.

In FIG. 5, when the leak current detector 19 detects a leak current, the flawed lid ejector 20 in the solid line position is displaced to the broken line position, and the flawed can lid is moved from the transfer path to the can lid stacker 21. Is discharged.

FIG. 1 shows a schematic diagram of the electrode portion, which is a chuck 1 for fixing a can lid.
1 indicates a state where 1 has risen and is at the top dead center (defect detection position). Reference numeral 9 is the bottom of the recessed hole, and 12 is the ground electrode on the chuck side.

Panels that are the bottom end of the revolution electrode and the top end of the can lid, using the can lid that has been previously confirmed to have flaws and the can lid that has been confirmed to have no flaws using the above-mentioned device. The gap between the faces is 0.5 mm, 1.0 mm, and 1.5, respectively.
mm so that the applied voltage is 4.2 to 5.0K
V is set to 0.2 KV interval, the detection leak current is 0.5 mA or more, the detection time per sheet is 0.097 seconds, and the revolution electrode rotates 4 times within 0.097 seconds. The results of setting and testing using an AC power supply are shown in Table 1 on the next page.

When the distance between the revolution electrode and the panel top 8 of the can lid was 0.5 mm, the applied voltage was 4.4 KV or more, and all the can lids with flaws were detected and discharged. The spacing is 1.0 mm and 1.5 m
In case of m, the applied voltage is 4.6 KV and 4.8 K, respectively.
All of the can lids with flaws were detected at V or more, and non-defective can lids without flaws were not discharged.

As described above, if a too high voltage is applied to the plastic film on the inner surface of the laminated material, the plastic film itself will be destroyed by the voltage, and the can lid without a flaw will be discharged in the same manner as the can lid with a flaw. However, such a phenomenon did not occur in this method, but it goes without saying that it is preferable to set the applied voltage as low as possible. From the results shown in Table 1, it can be said that it is more effective to set the distance between the revolution electrode and the can lid as close as possible in order to set the applied voltage low.

The can lids used in this test were mass-produced, and the panel height varied by ± 0.25 mm, and the distance between the top of the panel and the bottom of the recessed hole varied by ± 0.25 mm. It is unavoidable that such variations occur in mass-produced can lids, but this flaw detection method is
It was found that such variations can be sufficiently absorbed and it is practical.

The current value when a voltage of 4 to 5 KV is applied is estimated to be approximately 1 A. However, if the current value is left as it is, a spark occurs between the can lid and the metal plate of the can lid, and the surrounding plastic film. Burnt on the surface, but 1.5 MΩ
When the current value at the time of application was lowered using the resistor of, the discharge in the atmosphere between the metal plate and the metal plate at the time of detecting the can lid with a flaw was generated,
The discharged can lid has no abnormal appearance and can be reused for applications where corrosion resistance is not required. However, when the low antibody was 2 MΩ or more, detection of the can lid with a flaw became impossible.

The orbiting electrode can be used by binding conductive thin wires with a diameter of 0.05 to 0.2 mm and having a diameter of 1.0 to 5.0 mm, but when the diameter of the rivet recessed hole is 4.25 mm, , Bundled with 0.1mm diameter conductive thin wire, diameter 3.0m
It is preferably m.

The ground electrode 12 shown in FIG. 1 used for this test
Is in contact with the epoxy phenolic paint that is an insulator on the outer surface of the can lid, but this coating film is extremely thin. The distance between the electrode and the coating film is 3 mm, and the leakage current between the coating surface and the metal body is small. Is 0.5mA or more, the measured voltage is compared, and even if there is a coating film, the maximum is 0.1KV compared to the metal body.
However, when the can lid has a flaw and a leak current occurs in the metal plate of the can lid, the coating film is easily destroyed by an applied voltage of 4 to 5 KV. This shows that a leak current flows through the ground electrode.

FIG. 4 shows another embodiment of the electrode portion. The can lid 1 is directly attached to the can lid positioning elevating chuck 11 'by vacuum suction with its inner surface facing upward. Ground electrodes 22, 22 '
Is brought into contact with the cut edge where the metal base material around the periphery of the can lid is exposed.

When tested using this electrode under the same conditions as in the previous example, the same results as shown in Table 1 were obtained.
Therefore, such an earth electrode is also practical.
Table 2 shows the test results obtained by using the inspection apparatus, the detection mechanism, and the electrodes shown in the first embodiment, setting the detection conditions to be the same, and applying a high DC voltage.

When a direct current is used, the detection voltage can change greatly if the gap between the revolving electrode and the can lid changes a little, so it is possible to detect it. It can be said that the use of alternating current is more effective in absorbing the variation in the fixed position of the can lid above.

〔The invention's effect〕

In the present invention, the small electrode is revolved to scan the examination site of the subject, and the detection time is set to a minute time in which the electrode revolves twice or more. Since the revolution electrode always rotates at a constant speed, the revolution speed and the rotation speed of the revolution electrode during the minute time are constant, so the detection accuracy is high, and the can lid is in a predetermined position during the minute time. Since it is only fixed and there is no need to rotate the can lid, inspection can be performed with high efficiency.

The apparatus of the present invention is configured to fix the transferred can lid with a positioning chuck, raise the chuck to hold the can lid at a predetermined inspection position, and revolve the small electrode. Therefore, unlike the case of rotating the can lid, sliding contact between the can lid and the chuck is avoided, no scratches occur, the can lid can be stably fixed, and an inspected can lid is used. This is suitable for incorporation into a production line because it is only necessary to lower the chuck when transferring to the next process and the inspection process can be performed at high speed.

In addition, since the electrodes can be made small, a large amount of power is not required and the cost is low, and detection can be performed by applying a relatively low voltage of 4 to 5 KV, so that a normal plastic film may be destroyed. Absent.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an embodiment of an electrode used in the flaw detection method of the present invention, FIG. 2 is a plan view of an outer surface of an easy-opening can lid made of a laminated material to be inspected, and FIG. 1 is a cross-sectional view taken along the line AA in FIG. 1, FIG. 4 is a partial cross-sectional view showing another embodiment, FIG. 5 is a schematic view of an inspection apparatus, FIG. 6 is a block diagram showing an electric system, and FIG. Figures and 8 are schematic diagrams showing the prior art. 5; Tab fixing rivet 6; Rivet recessed hole 7; Recessed peripheral wall 11, 11 '; Can lid positioning lift chuck 12; Earth electrode 14; Revolution electrode 15; Revolution electrode holder 18; High voltage generator 19; Leak current detector 20; Lid ejector with flaw

Claims (2)

[Claims] 1. A plastic film is laminated on one surface of a metal plate base material for a can lid, and a film is formed in the recessed hole portion of the inner surface of a rivet for tab attachment of an easy opening can lid formed with the laminated surface as an inner surface. In the method for detecting whether or not there is a small electrode that revolves around the center axis of the can lid and has a radius passing through the center of the recessed hole, the inner surface of the can lid is rotated at a predetermined distance from the inner surface of the can lid. Then, a predetermined high voltage is applied to the revolving electrode during a minute time in which the electrode revolves for two revolutions or more, and a predetermined current value or more is applied between the revolving electrode and the can lid in contact with the ground electrode. A flaw detection method for a laminated material can lid, comprising detecting whether or not a current flows as a leak current. 2. An easy opening can lid formed by laminating a plastic film on one surface of a metal plate base material for a can lid and forming the laminated surface of the film as an inner surface, with the inner surface facing upward, intermittently detecting one by one. Means for transferring to the container, a positioning chuck for fixing the can lid transferred to the detector and raising and holding the can lid at a predetermined detection position during detection, and an inner surface of the can lid on the inner surface side of the can lid. Revolving electrode having a small electrode that revolves around the center axis of the can lid with a radius passing through the center of the recessed hole at a predetermined interval, and a predetermined high voltage for a minute time when the electrode revolves for two or more revolutions. Defect detection of a laminated material can lid, comprising means for applying to an electrode and means for detecting that a leak current of a predetermined current value or more flows between the revolution electrode and the ground electrode. apparatus.