JP3933944B2 - Non-contact inspection method for high frequency aluminum seals - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-contact inspection method for high-frequency aluminum seals, and more specifically, the quality of a seal when a container inner lid composed of at least an aluminum foil and a synthetic resin molded member is sealed with aluminum foil by high-frequency induction heating. The present invention relates to a non-contact inspection method for a high-frequency aluminum seal that is determined directly from an infrared thermal image obtained from the upper surface or from a histogram obtained by data processing of such an infrared thermal image.
[0002]
[Prior art]
Conventionally, as an inspection method using infrared rays, for example, Japanese Patent Laid-Open No. 62-28650 “Inspection Method for Adherence of Foreign Objects” and Japanese Patent Laid-Open No. 7-101423 “Packaging Container Adhesion Inspection Device” are known. More specifically, the former applies a thermal change to the object to be inspected from the outside, and measures the temperature difference caused by the heat capacity of the foreign matter adhering part of the object to be inspected with an infrared detector, thereby detecting the blister of the food. Indirect automatic determination of the adhesion of the packing material to the inner surface of the container top lid of the packaged product, and the latter infrared rays are emitted from the upper surface and both side surfaces of the packaging container having the hot melt adhesion site. By detecting with a radiation thermometer, it is possible to inspect the adhesion failure of the bonding location of the packaging container in a non-contact manner from the outside of the packaging container. Although these are the same as the present invention in that infrared thermal images are used, as will be understood from the description below, due to differences in the inspection target (inspection location) and the infrared (source) to be captured. It is completely different from the invention.
[0003]
Liquid, powdery or granular seasonings such as mayonnaise, dressing, tomato ketchup, soy sauce, sauce, etc. The (bottle) is filled, and the container opening is in circulation in the form of being covered with a non-metallic resin cap (outer lid). These products are desired to have an inner lid from the viewpoint of safety and the impression of hygiene received by consumers during the distribution process.
[0004]
As such an inner lid, there is a sealing method by heating a high frequency induction aluminum foil. That is, for example, an aluminum foil laminated with a heat-meltable resin film such as a polyethylene film via an adhesive layer (hereinafter also referred to as an aluminum seal laminate) is formed on the donut shape of the opening of a container filled with the contents. Cut to a circle that is slightly larger than the outer diameter of the upper edge of the donut shape so that it covers the edge (preferably, a tab is attached so that it can be easily removed when the lid is removed later when opened). Covering the container opening with the resin film face down, preferably from the outside (preferably provided with a donut-shaped ridge on the inner bottom so that the aluminum foil can be well pressed against the upper edge of the container opening) Put the lid (cap), and pass the high-frequency induction heating sealer in this state. The conceptual diagram of the relationship between each part is shown in FIG.
[0005]
Thus, when it passes through the high-frequency sealer, an eddy current flows through the inner edge of the circular cut piece of the aluminum foil, and the aluminum foil is heated by this eddy current. The cut piece of aluminum foil (aluminum seal) is pressed against the top edge of the donut shape at the opening of the bottle (container) by the outer lid (cap) (protrusion provided on the inner bottom of the cap), and the heat generated by the aluminum seal Melts the resin of the bottle in the part (A part of FIG. 2) with which the aluminum seal is in contact, and then the melted resin is solidified by natural cooling. As a result, an aluminum seal (inner lid) is adhered to the bottle opening, and a product having an outer lid on the aluminum seal is completed.
[0006]
However, the high-frequency induction heating seal performed in this way is not always performed well, and the cap (top cover) is loosened, the slanted cap and the two aluminum seals are stacked, the heating temperature is too low, and the heating temperature is low. Incomplete defect seals may occur due to reasons such as being too high, contents (contents) adhering to the seal, notch on the seal surface, no aluminum seal, etc.
[0007]
Therefore, for example, using a belt conveyor, the resin container is filled with the contents (contents), a circular inner lid of aluminum foil is placed on the upper edge of the donut shape of the container opening, and this is covered with an outer lid (cap). Production in which the product is continuously sealed by pressing the upper edge of the container opening and subjecting the aluminum foil to high-frequency heat fusion to the upper edge of the container opening by high-frequency induction heating in this state. It is strongly desired that a product with an incomplete seal as described above can be easily detected on the line and such a product (defective product) can be eliminated.
[0008]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method for easily detecting defects in a high-frequency aluminum seal as described above under the background of the prior art described in the previous section.
[0009]
[Means for Solving the Problems]
As a result of diligent research to achieve the object described in the preceding paragraph, the present inventor attached a lid (outer lid) with an aluminum seal inner lid to the upper edge of the resin container opening donut shape, and allowed to pass under the high-frequency sealer. When the aluminum seal laminated material is heated in a non-contact manner and the lower layer of the heat-meltable resin is fused to the upper edge of the container mouth portion donut shape, the heat generated in the aluminum seal foil portion is the melted portion of the donut shape, that is, the seal. The situation is transmitted to the outer surface through the outer lid, but the state of heat conduction is captured in a non-contact manner as an infrared thermal image with an infrared camera, and this is reproduced in color by the image inspection processing device in color distribution on the outer surface of the upper lid. Then, it was found that it was possible to easily determine whether or not the aluminum seal was bonded in a good state from the data analyzed by this shape, and the present invention was completed based on such knowledge.
[0010]
That is, the present invention places at least a synthetic resin molded member and an inner lid of a metal piece such as an aluminum foil on the donut-shaped upper edge of the resin container opening, and this is placed on the container opening with a resin outer lid. In this state, it was subjected to high frequency induction heating in this state, and the synthetic resin molding member pressed against the lower surface was partially melted by heat generation of the metal piece, and was heated and fused to the upper edge of the container opening donut shape. In this case, following the high frequency induction heating process, the upper surface of the cap is photographed with an infrared thermal image camera, and the quality of the aluminum seal is determined based on the shape and / or data analysis of the obtained infrared thermal image. A non-contact inspection method in which the data analysis is 1) detection of a high temperature value above a certain measured temperature, and 2) a synthetic resin molded portion welded to the upper edge of the donut shape of the resin container opening Detection by the ratio of the length of the doughnut-shaped long axis and the length in the uniaxial direction or shape abnormality, 3) the flow direction of the heat-welded portion donut-shaped resin container formed on the upper edge of the donut shape of the resin container opening Centerline temperature distribution detection 4) Use of at least one of temperature distribution detection of a donut-shaped centerline of a doughnut-shaped synthetic resin molded member welded to the upper edge of the donut-shape of the resin container opening The present invention relates to a non-contact inspection method for high-frequency aluminum seals.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0012]
A synthetic resin molded member and an inner lid of a metal piece (aluminum seal laminate) such as aluminum foil are placed on the donut-shaped upper edge of the resin container opening, and the container is opened with a resin outer lid (cap). In this state, the synthetic resin molding member positioned on the lower surface of the aluminum foil by being subjected to high frequency induction heating in this state is subjected to high frequency heating and fusion to the upper edge of the container opening itself according to a conventional method. be able to.
[0013]
The surface of the object is photographed with an infrared thermal image camera, the obtained thermal image is processed with data, and the temperature distribution of the surface of the object is displayed, for example, in color (high temperature part is red, low temperature part is blue, and intermediate part is For display with a histogram, etc., a device comprising a system such as a commercially available infrared camera, data processing, display or the like can be used as appropriate (for example, NEC Corporation infrared radiation thermometer “ "Thermo Tracer", Mitsubishi Electric Corporation High-speed Thermal Image Analyzer "Mitsubishi Thermal Imager", Nippon Avionics Co., Ltd. Infrared Thermal Imager (TVS Series), JEOL Ltd. Infrared Temperature Analyzer "Thermo Viewer" (JTG-6000) Series), etc.).
[0014]
A commercially available apparatus can be used for the high-frequency oscillator used in the present invention. For example, “High Frequency Oscillator SST-20” manufactured by Shimada Rika Co., Ltd. is preferably used.
[0015]
A feature of the present invention is that part of the synthetic resin molded member laminated on the lower surface of the metal piece is melted by heat generated in the metal piece (aluminum foil) by high frequency oscillation, and the donut-shaped upper edge of the resin container mouth is The thermal distribution of the heat generated when sealed through the outer top of the outer lid to the outer upper surface of the outer lid is captured by the infrared thermal image camera from the top, and the obtained infrared thermal image data is processed to create the outer side of the outer lid. Color distribution or histogram analysis of the temperature distribution on the upper surface (It is well known that the display by data processing can be performed in real time), and it is well sealed based on these display or analysis If they match with those in the case of the finished product, it is determined that the seal is good, and if they do not match, it is determined that the seal is defective, and the reference data is set and an abnormal value is detected. It is to inspect the sealing contactless manner between.
[0016]
This will be described more specifically with reference to FIG. FIG. 2 shows the heat conduction to the upper surface of the cap (outer lid) during heating of the aluminum seal and a histograph captured by the infrared thermal image camera from the upper part toward the cap. The heat generated by the aluminum seal is also transmitted to the cap portion (portion A in FIG. 2), and it can be seen from the upper part of the cap that the temperature of the donut-shaped portion is higher than the temperature inside the donut. It is possible to determine the state of sealing adhesion fairly accurately in the form of temperature distribution.
[0017]
That is, when a clean donut shape as shown in FIG. 2 is observed (however, when a tab is attached to the inner lid of the aluminum foil, the outer edge of the donut image is slightly chipped), If it can be determined that a good aluminum seal was applied, and other shapes were observed, (1) the cap (outer lid) was not fully tightened depending on the shape, and the aluminum seal (inner lid) was a bottle. (Container) Because it was not well pressed against the upper edge of the donut shape of the opening (2) Because there was a part where the aluminum seal floated by tightening the diagonal cap, (3) The bottle (the upper edge of the donut shape of the opening) Since the aluminum seal bonding surface was not flat and did not properly contact the aluminum seal, (4) the contents did not adhere to the aluminum seal bonding surface and the temperature did not rise sufficiently. Because the output of the high frequency sealer was too large and the temperature rose too much, (6) The output of the high frequency sealer was too small and the temperature did not rise sufficiently, (7) Because there was no heating by the high frequency sealer, (8) Aluminum Since the seal was not attached, (9) since the aluminum seal was attached in an overlapping manner, it is possible to estimate various causes of the malfunction. Therefore, by using this result, it is possible to inspect the total number of on-line judgments on the quality of the aluminum seal adhesion of bottles (containers) filled with contents flowing on the conveyor.
[0018]
The shape of the donut is displayed as an ellipse on the screen when the present invention is implemented in the actual production process, even though the resin container mouth is circular. This is due to the fact that the heat-sealed seal of the resin container is performed on a belt conveyor that operates. That is, since the resin container always moves at a constant speed, it appears on the screen as an elliptical donut that is crushed in the moving direction. However, even this elliptical image does not hinder the analysis or the judgment with the naked eye.
[0019]
Whether the aluminum seal is good or bad can be judged based on the histogram obtained by infrared image data processing. Similarly, if the seal is good and the histogram of the product to be inspected is compared, whether or not they match each other? To judge whether the seal is good or bad.
[0020]
To remove products (defective products) that are judged to be poorly sealed because their images or histograms do not match the images or histograms of well-sealed products (good products) against the display If an image of a seal failure appears, or if the above verification is performed automatically and mechanically automatically, the product is displayed as No Good on the display. If this is the case, the defective product can be manually removed from the line, but the result of the verification performed automatically automatically is converted into a drive signal for the defective product elimination device and automatically It is possible to eliminate defective products.
[0021]
On the other hand, in the temperature distribution data analysis of the image projected on the screen, 1) (abnormally high temperature) out of all the measured temperatures, a high temperature value above a certain level, 2) (abnormal shape of the seal part) made of resin Detection of the ratio of the doughnut-shaped long axis and the length in the uniaxial direction of the synthetic resin molded member welded to the upper edge of the donut shape of the container opening or a shape abnormality, 3) (sealing temperature distribution) of the resin container opening Thermal distribution detection of the center line in the flow direction of the doughnut-shaped resin container formed on the top edge of the donut shape, 4) (Seal temperature change rate) welded to the top edge of the donut shape of the resin container opening At least one of the temperature distribution detection of the donut-shaped center line of the doughnut-shaped synthetic resin molded member can be used, or a plurality can be used in combination.
[0022]
1): (Abnormally high temperature) Among the total temperatures measured, the standard for detecting a high temperature value above a certain level is determined by the combination of the material of the resin container and the synthetic resin forming member used for the aluminum seal member. In general, when high-density polyethylene is used for the synthetic resin forming member, the maximum temperature is 140 ° C. because the melting points are 120 to 140 ° C. and 107 to 120 ° C., although there are differences depending on the manufacturer. On the other hand, heat generated by heating by high frequency oscillation is transmitted from the top surface inside the cap to the top surface outside the cap. Since the thermal imaging camera measures the temperature of the upper surface of the cap, the melting temperature is measured through heat conduction to the cap. Therefore, the measured temperature is measured at a considerably lower temperature than the melting temperature. Actually, how much the apparent temperature outside the cap is detected lower than the melting temperature depends on the material of the cap, the structure, and the high frequency aluminum sealing conditions (room temperature, high frequency oscillation time, resin container moving speed, etc.). Therefore, it is necessary to examine and decide how often the abnormally high temperature value is set.
[0023]
2): (Abnormal shape of seal part) Detection of the ratio of the doughnut-shaped long axis and the length in the uniaxial direction of the synthetic resin molded member welded to the upper edge of the donut shape of the resin container opening or the abnormal shape This will be described more specifically. Since the plastic container placed on the bag is moving on the belt conveyor, the image displayed on the infrared image analysis CRT screen for detecting the sealing property is compared with the X axis where the movement direction Y axis is perpendicular to the movement. short. Therefore, it is possible to inspect the X / Y ratio to be within a certain range or to set the upper and lower limits for each of the X and Y values.
[0024]
3): (Seal temperature distribution) The temperature distribution of the center line in the flow direction of the doughnut-shaped resin container formed in the donut-shaped upper edge of the resin container opening is detected by the donut-shaped meat part. If the temperature distribution of the center line in the flow direction of the resin container is shown on the graph with the temperature on the horizontal axis and the frequency on the vertical axis, the temperature distribution in the hollow part will be a curve with two maximum values. It can be detected by storing it in the memory and comparing it with the measured value.
[0025]
4): (Seal temperature change rate) The temperature distribution of the doughnut-shaped donut center line of the synthetic resin molded member welded to the upper edge of the doughnut-shaped resin container opening is mainly detected by the disconnection of the donut shape, that is, heat It is convenient for detecting a broken portion that is not welded. On the CRT screen, the X axis is 0 to 360 degrees along the donut center line, and the Y axis records the temperature. If the curve shows a straight line parallel to the X axis or a loose curve, it can be considered that there is no sudden change in temperature (break zone).
[0026]
An example of an inspection system according to the present invention is shown in FIG.
[0027]
When the conveyor moves fast and the line speed (bottles / minute) is large, it is advisable to adopt a high-speed thermal image analyzer that can catch the temperature distribution on the upper surface of the upper lid described above even at such a speed. Not too long.
[0028]
Also, if the conveyor moving speed is high and the container moving speed increases, the front of the container lid in the direction of travel cools down, and the resulting infrared thermal image does not form a clean donut shape even when the seal is good. Needless to say, it is possible to determine the quality of the seal by comparing the thermal image of a good product with the thermal image of the product to be inspected as a reference.
[0029]
【Example】
The following examples further illustrate the present invention.
[0030]
(Preparation and assembly of resin containers and high-frequency seal members)
An aluminum seal laminate (total thickness 30 μm) in which a synthetic resin molded member / adhesive / aluminum foil / cellophane thin film is laminated on the upper edge of the donut shape of the resin container opening is used as an inner lid, and this is a screw-in red resin A test sample was prepared by winding and crimping the container opening on the upper edge of the container opening with a torque of 7.5 kg / cm. Resin containers were prepared for 5000 containers each having a capacity of 250 g, 400 g, 600 g, and 1000 g, each filled with mayonnaise. In addition to this, various types of resin outer lids were prepared in yellow, orange and white.
[0031]
(Shooting of high-frequency seal and seal state)
The prepared resin container is placed on a cage for stabilization on a belt conveyor, moved at 530 cm / s, and fixed at a certain position under the coil of a high-frequency oscillator (“SST-20” manufactured by Shimada Rika Co., Ltd.). Was maintained and moved in the water direction. In this state, it is subjected to high-frequency induction heating at an output of 89 to 106 V and 55 to 75 A, and the synthetic resin molding member pressed against the lower surface is partially melted by the heat generation of the aluminum foil and heated to the upper edge of the container opening donut shape. Fused. Subsequent to the high-frequency induction heat treatment, the upper surface of the cap was photographed with an infrared thermal image camera, and a donut-shaped temperature distribution image was projected on the obtained TV screen.
[0032]
(Analysis items)
1) (Abnormally high temperature)
Detection of a high temperature value above a certain level among all measured temperatures,
2) (Abnormal shape of seal part)
Detection by the ratio of the donut-shaped long axis and the length in the uniaxial direction of the synthetic resin molded member welded to the upper edge of the donut shape of the resin container opening, or by a shape abnormality,
3) (Seal temperature distribution)
Temperature distribution detection of the center line in the flow direction of the heat-welded portion donut-shaped resin container formed at the upper edge of the donut-shaped resin container opening,
4) (Seal temperature change rate)
The temperature distribution detection of the donut-shaped centerline of the doughnut-shaped synthetic resin molded member welded to the upper edge of the donut shape of the resin container opening was simultaneously performed 1) to 4).
[0033]
(Analysis result)
The donut-shaped temperature distribution could be visualized colorfully from the CRT screen. This made it possible to make an instant determination even with the naked eye. Further, for the sake of accuracy, the above analysis items were detected for all samples, and the data was stored. In the actual process analysis, when an abnormal value is detected in light of the above analysis items, the data stored in the computer is extracted for the sample, the cause of the abnormality is analyzed, and the subsequent measures can be taken immediately. Analysis item 1): An example detected at an abnormally high temperature was detected when high-frequency sealing was intentionally performed again after high-frequency sealing. A part of the aluminum foil and a part of the upper edge of the resin container mouth were loosened, and an abnormally high temperature of the part was detected in a state where the part was in point contact with the cap or the oblique cap. Analysis item 2): The abnormal shape of the seal part is an abnormality in the feeding and moving speed of the resin container. From analysis item 3): (Seal temperature distribution), when the aluminum seal laminate was not set, an abnormally low temperature was detected when the aluminum seal laminate was set twice. Analysis item 4): (Seal temperature change rate) was detected when a portion of the seal was not sealed.
[0034]
【The invention's effect】
According to the present invention, a resin container (bottle) is filled with contents, and an aluminum seal laminate (inner lid) is attached to and attached to the top surface of the outer lid, and passes under the output of the high frequency sealer. The synthetic resin forming member in the lower layer of the seal laminate and the quality of the fusion seal when fused to the upper edge of the opening of the container can be easily and thoroughly tested, and the quality control is extremely efficient and Can be done effectively.
[Brief description of the drawings]
FIG. 1 is a cutaway view showing a seal portion of a high-frequency seal according to the present invention.
FIG. 2 shows heat conduction to an upper surface of a cap (outer lid) during heating of an aluminum seal and an infrared image histogram thereof.
FIG. 3 shows an example of an inspection system according to the present invention.

Claims (1)

At least a synthetic resin molded member and an inner lid of a metal piece such as aluminum foil are placed on the upper edge of the donut shape of the resin container opening, and this is pressed against the upper edge of the container opening with a resin outer lid. When the synthetic resin molded member pressed against the lower surface is partially melted and heated and fused to the upper edge of the donut shape of the container opening by high-frequency induction heating in a state and heat generation of the metal piece, the high-frequency induction In a non-contact inspection method for high frequency aluminum seals, the upper surface of the outer lid is photographed with an infrared thermal image camera following the heat treatment, and the quality of the aluminum seal is determined based on the shape and / or data analysis of the obtained infrared thermal image. there, the method determines based on the shape is a method of the form of temperature distribution of the donut-shaped portion is determined by whether the donut shape was observed, the total temperature which the data analysis 1) was measured Among them, detection of a high temperature value above a certain level, 2) detection of the ratio of the doughnut-shaped long axis and uniaxial length of the synthetic resin molded member welded to the upper edge of the donut shape of the resin container opening, or shape abnormality 3) Detection of the temperature distribution of the center line in the flow direction of the heat-welded portion doughnut-shaped resin container formed at the upper edge of the donut shape of the resin container opening 4) On the upper edge of the donut shape of the resin container opening A non-contact inspection method for a high-frequency aluminum seal, characterized by using at least one of temperature distribution detection of a doughnut-shaped center line of a welded synthetic resin molded member.

Images