JPS6242692B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing beverage cans filled with inert gas using a squeeze iron can having novel characteristics.
More specifically, the present invention relates to a method for producing inert gas-filled cans that have excellent quality assurance of contents and also reduce packaging costs. Seamless cans formed by drawing and ironing metal materials are used exclusively as internal pressure cans to accommodate contents with self-generating pressure, such as carbonated drinks, and their internal pressure resistance strength must be 7 kg/cm ² or more. requested. On the other hand, as a method for preserving non-carbonated beverages such as fruit juice without reducing their flavor, an inert gas such as nitrogen gas is aerated through the fruit juice before it is filled into a sealed container to dissolve the gas to saturation. A method of filling and sealing has been proposed (for example,
Publication No. 19947). A well-known seamless can made by drawing and ironing process,
The inventors of the present invention have discovered that many problems still arise when the method is used to manufacture the above-mentioned inert gas-filled beverage cans. That is, in the case of canned beverages such as fruit juice that require sterilization, it is mandatory to fill the contents, store the sealed cans for a certain period of time, and then give them for inspection. Here, the term "percussion inspection" refers to a test that detects abnormalities in the internal pressure of the can due to poor sealing or deterioration of the contents by using the sound produced when tapping the bottom of the can. The well-known seamless cans were originally designed to withstand internal pressure, and since the cans are filled with inert gas at a pressure higher than atmospheric pressure, poor sealing cannot be determined by percussion inspection. We are faced with a problem that is extremely difficult.
Furthermore, although known squeeze ironing cans may be satisfactory for the purpose of accommodating high-pressure contents, they are still unsatisfactory for the purpose of reducing the amount of metal material used, thereby reducing packaging costs. It was from. The present inventors have developed a seamless can by drawing and ironing, in which the thickness of the bottom wall and the body wall are within a specific range, and the internal pressure resistance is within a specific range, for manufacturing beverage cans filled with inert gas. It has been found that when used in the field, the suitability for hammer inspection is significantly improved, and as a result, the quality assurance of the contents is reliably improved, and packaging costs are also reduced by saving on the amount of metal material used. That is, an object of the present invention is to provide a method for producing an inert gas-filled beverage can that is suitable for punch inspection and, as a result, has excellent quality assurance of the contents. Another object of the present invention is to provide a method for producing an inert gas-filled beverage can that saves the amount of metal material used and, as a result, reduces packaging costs. Still another object of the present invention is to provide a method for manufacturing beverage cans filled with inert gas using a squeeze iron can having novel characteristics. Still another object of the present invention is to provide a method for producing an inert gas-filled beverage can that is excellent in flavor retention and preservation of the contents. According to the present invention, it is formed by drawing and ironing a metal material, and the thickness (Dd) of the body wall is 0.10 to 0.10.
0.14mm, the ratio of the bottom wall thickness (Db) to the body wall thickness (Dd) (Db/Dd) is in the range of 1.5 to 2.2, and the internal pressure resistance is 3Kg/cm ² or more and 7Kg/cm Seamless cans with a capacity of less than ² are filled with non-carbonated beverages and an inert gas mainly composed of nitrogen, the can lids are sealed, and the resulting inert gas-filled cans are inspected to identify poorly sealed cans. Provided is a method for producing an inert gas filled canner characterized by detecting. In FIG. 1 showing a schematic cross-sectional structure of a seamless can used in the present invention, a seamless can (can body member)
1 consists of a bottom wall part 2 and a cylindrical body wall part 3 continuous to the bottom wall part 2. The periphery of the body wall portion 3 of this can body member 2 and the connection portion 4 between the body wall portion 3 and the bottom wall portion 2
There are virtually no seams. This can body wall member 3 is made by drawing and ironing a metal material.
The bottom wall 2 is made of substantially unironated metal material and is relatively thick. A flange 5 is provided on the upper edge portion of the body wall portion 3, and is filled with a content beverage and nitrogen gas, which will be described later.
After sealing, a sealing portion (sealing portion) 7 is formed between the flange 5 and the peripheral edge of the can lid member 6 that covers the flange 5, as shown in FIG.
If desired, a corrosion-resistant protective resin coating 8 is provided on the inner surface of the can body member 1 and the inner surface of the can lid member 6 to prevent direct contact between the contents and the metal material.
will be applied. A smooth spherical protrusion (dome) 9 can be provided on the bottom wall 2 facing inward, thereby preventing the bottom wall 2 from protruding outward due to the pressure of the contents. You can improve your sitting posture. Further, a neck 10 is provided at the upper edge of the body wall 3 of the can body member 1, so that the tightening portion 7 between the can body flange 5 and the peripheral edge of the can lid member is located outside the circumferential surface of the body wall of the can body member. By preventing the container from protruding in the opposite direction, it is possible to reduce the storage volume when packaging the case or canned product. The metal material constituting the housing may be any metal material, such as steel plate; tin plate, galvanized steel plate,
Various plated, electrolytically treated or chemically treated steel plates such as chromium-treated steel plates; light metal plates such as aluminum plates; or composite materials thereof are used. Preferred metal materials are tinplate and aluminum. An important feature of the present invention is that the thickness (Dd) of the trunk wall portion 3 is 0.10 to 0.14 mm, particularly 0.10 to 0.11 mm;
Thickness of bottom wall 2 (Db) and thickness of trunk wall 3 (Dd)
(Db/Dd) is 1.5 to 2.2, especially 1.5 to 2.0
7 if it is within the range and the internal pressure resistance is 3Kg/cm2 ^or more
The aim is to use seamless cans with a weight of less than Kg/cm ² , especially in the range of 4.0 to 6.0 Kg/cm ² . As already mentioned above, when conventionally used seamless cans are used to manufacture inert gas-filled cans, they lack suitability for hammer inspection, making it difficult to guarantee the quality of the contents. On the other hand, according to the present invention, the above-mentioned Db/Dd ratio is 2.2 or less, particularly 2.0 or less, and the internal pressure resistance is less than 7Kg/ ^cm2 , especially 4.0.
Selecting a seamless can with a weight of less than Kg/cm ² and using it for this purpose will significantly improve the perforation suitability of beverage cans filled with inert gas, making it possible to detect poorly sealed cans through percussion.
It is possible to do this with a probability of 100% or close to this. In this specification, the term ``discussion'' refers to Japanese Patent Application Laid-Open No. 53-119087.
This refers to a test performed using a device based on the principle described in the publication. According to this device, an electromagnetic pulse is applied to the bottom of the canned sample to be measured, causing a natural vibration in the bottom of the can, and Measurement is performed by converting sound into an electrical signal using a microphone, and determining the natural frequency of this electrical signal using the autocorrelation method or fast Fourier transform. In this percussion test, if the can is poorly sealed, the natural frequency will generally shift to a higher frequency side. The seamless can used in the present invention is
Compared to conventionally known seamless cans, the degree of sealing, that is, the dependence of the natural frequency on fluctuations in internal pressure is significantly greater, and as a result, the accuracy of detecting poorly sealed cans by inspection is significantly improved. Note that depending on the form of the seamless can, the natural frequency may shift to a lower frequency side due to poor sealing. The difference in vibration frequency is significant, making it easy to detect poorly sealed cans. In general, when performing a hammer test for can filling, etc., the area to be hammered has a wide flat area, and the can body is not deformed during the hammer test, the better the suitability for the hammer test. Therefore, when internal pressure is applied as in the present invention, the can body is difficult to deform due to the internal pressure, and the part to be hammered, that is, the dome portion 9, usually deforms in the direction outside the can due to the internal pressure. A flat portion is formed in the upper part of the dome, improving suitability for hitting. This percussion detection device is commercially available from Toyo Seikan Co., Ltd. under the trade name Electro Detector. FIG. 3 is a diagram showing the relationship between the difference in natural frequencies (Δν) between a normal can and a poorly sealed can and the can bottom pressure resistance (Pr) in a percussion test. This third
In the figure, the ratio (Db/Dd) of the bottom wall thickness (Db) to the side wall thickness (Dd) is 1.6, 2.2 and
Three curves are shown for a value of 2.5. The can bottom pressure strength Pr in FIG. 3 is adjusted by changing the shape of the can bottom, that is, the dome shape, so that a predetermined pressure strength can be obtained. However, the results shown in Figure 3 show the following fact. That is, in a seamless can where the ratio of Db/Dd mentioned above is within the range of the present invention, that is, 2.2 or less, particularly 2.0 or less, the can bottom pressure resistance is 3 kg/cm ² or more and 7 kg.
In the range less than Therefore, in a conventional seamless can with a Db/Dd ratio of about 2.5, the can bottom pressure strength Pr is 3.
In the range of Kg/cm ² or more, the above-mentioned difference in natural frequencies △ν is in the extremely small range of 100 Hz or less, and it is extremely difficult to accurately determine the difference between a normal can and a poorly sealed can by percussion. Become. Further, the above-mentioned ratio of D _b /D _d is 1.5 or more and the internal pressure strength is 3 Kg/cm ² or more, which has an important meaning regarding the shelf life of the contents. Beverages such as fruit juices that are filled into seamless cans undergo heat sterilization before being filled into the cans, but in order to increase their shelf life, the cans are subjected to post-sterilization treatment using a pasteurizer, etc. after filling. It becomes important. Since the seamless can used in the present invention has the above-mentioned characteristics, it becomes possible to perform a subsequent sterilization treatment, thereby further improving the shelf life of the contents. Another notable feature of the present invention is the thickness of the trunk wall (D
_d ) and the thickness of the bottom wall (D _b ) within the above-mentioned ranges, sufficient pressure resistance is ensured for inert gas-filled beverage canning applications, and the amount of metal material used can be reduced compared to conventional Compared to seamless cans, it is possible to save 20 to 5% by weight, which makes it possible to considerably reduce packaging costs. The seamless can used in the present invention can be easily formed by drawing and ironing methods that are known per se, except that the thickness D _d of the body wall and the thickness D _b of the bottom wall are within the above-mentioned ranges. can be manufactured. The internal pressure resistance of the can depends on the thickness and shape of the bottom wall. Thus, the seamless can with the internal pressure resistance specified in the present invention can be obtained by selecting a certain thickness from the above-mentioned range of body wall thicknesses and/or by adjusting the height of the inwardly protruding dome. This can be achieved by making it lower than that of conventional seamless cans.
Suitable dome heights are in the range 3 to 10 mm, with the added benefit of increasing internal volume by reducing the dome height. Filling with the non-carbonated beverage and inert gas and sealing by rolling may be performed by means known per se. Examples of non-carbonated beverages include various fruit juices, vegetable juices, synthetic or half-combined fruit juices, various soups, various nectars, coffee, black tea, lactic acid drinks, stews, and the like. These beverages are sterilized in hot water, cooled to low temperatures, and saturated with inert gas before being filled into cans. At this time, if desired, inert gas may be added and blown into the cans when the cans are rolled up. You can also do it. The inert gas pressure inside the canner is preferably in the range of 1.05 to 2.0 Kg/cm ² (gauge) in terms of flavor retention and preservability of the contents under standard conditions. In the present invention, it is also important to use an inert gas mainly composed of nitrogen. That is, when filling with an inert gas mainly composed of nitrogen gas, there is an advantage that pressure changes with respect to temperature changes are significantly smaller than when filling with carbon dioxide gas such as carbonated drinks. That is, the solubility of carbon dioxide gas in beverages is quite high at low temperatures and decreases at high temperatures, so the internal pressure of carbonated beverage cans increases significantly as the temperature rises. On the other hand, in the case of nitrogen gas, the amount dissolved in the beverage is originally small, so even if the temperature rises, the increase in pressure is relatively small. Therefore, in the present invention, it is possible to reduce the thickness (D _b ) of the bottom of the can. The cans filled with contents and sealed with can lids are subjected to post-sterilization treatment using pasteurizers, can warmers, etc., and are made into products. The internal pressure strength of a seamless can refers to the strength when pressure is applied to the inside of the can using a measuring instrument equipped with a pressure gauge to cause deformation buckling in which the dome of the bottom of the can protrudes to the outside of the can. The invention is illustrated by the following example. Example 1 Approximately 130 mm of prite tin plated wire mesh board with a base thickness of 0.16 mm
Punch it out into a disc with a diameter of , and form it into a round shape with an inner diameter of about 53 mm between a drawing punch and a drawing die according to the usual method. Next, it was ironed using a combination of ironing punch and ironing die. The dimensions and physical properties of this can body are as follows. Bottom wall thickness (D _b ) 0.16mm Body wall thickness (D _d ) 0.10mm D _b /D _d 1.6 Can body inner diameter 53 mm Can body height 135 mm Can body volume 300 ml Can body weight 25.0 g Compressive strength 3.1 Kg/cm ² After degreasing and cleaning the inside and outside surfaces of this can body, paint was applied. After that, the fruit juice drink is sterilized at 93 to 95℃, cooled to below 5℃, then nitrogen gas is filled into the sealed can body, the can lid is double-sealed, and the final product is sealed. It was sterilized by heating during the sterilization process. After the cans packed using the nitrogen gas filling method were subjected to actual can storage tests for one week and six months, the cans were opened and a panel of 10 people tested the contents and evaluated the flavor. Furthermore, the inner surface of the can was also observed after opening. As a result, the flavor of the case of the present invention did not substantially deteriorate even after being stored for 6 months, and no abnormality such as corrosion was observed on the inner surface of the case. Furthermore, in order to clarify the excellent effects of the present invention, a control case other than the present invention was prepared in the same manner as in Example 1 above, except for the following changes. (1) Control case A A case similar to Example 1 except that the bottom wall thickness was 0.32 mm. (2) Control case B A case similar to Example 1 except that it was hot-filled according to the conventional method, the atmosphere was replaced with water vapor, and then double-sealed. The can weight and flavor test results were compared for the two types of control cans and the can of Example 1.

[Table] The above results show that by selecting within the range specified in the present invention, the weight of the can can be significantly reduced and a method for producing a can with good content suitability can be obtained. Example 2 A rolled aluminum plate with a thickness of 0.24 mm is punched into a disc with a diameter of 150 mm, and according to a conventional method, it is formed into a circular plate with an inner diameter of about 72.2 mm between a drawing punch and a drawing die. Next, this pot-shaped molded product is subjected to a reprocessing process, and then re-drawn to form a pot-shaped molded product (inner diameter approximately 65.4
mm) was ironed in the same manner as in Example 1. The dimensions and physical properties of this can body are as follows. Bottom wall thickness (D _b ) 0.24mm Body wall thickness (D _d ) 0.14mm D _b /D _d 1.71 Can body inner diameter 65.4 mm Can body height 122 mm Can body volume 410ml Can body weight 12.3g Pressure strength 3.0Kg/ cm ² This can body was coated on the inside as in Example 1,
The fruit juice beverage was filled and canned using the nitrogen filling method. As a result, as in Example 1, it was confirmed that the contents had excellent preservability. Example 3 Canned food prepared according to Example 1 (Db/Dd=
1.6), and Db/Dd=2.2 and Db/Dd=2.5, a comparative test was conducted on the sealing performance using an automatic punching machine. Here, the automatic percussion machine is one that strikes an object with an electromagnetic pulse to generate a natural frequency, receives the sound through a microphone, and measures the electric signal as the natural frequency using a Fourier transformer. As a result, it was confirmed that the hammer testability, that is, the resolution of the sealing performance test, was significantly different between Example 1 and the case with Db/Dd=2.5. FIG. 3 shows the measurement results. Here, Ρr represents the pressure resistance of the can bottom, and Δν represents the difference in natural frequency between a normal product and a poorly sealed can.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a seamless can used in the present invention, Fig. 2 is a schematic cross-sectional view showing the tightening portion between the can body and the can lid, and Fig. 3 is a schematic diagram of the seamless can used in the percussion test. FIG. 2 is a diagram showing the relationship between the pressure resistance and the difference in fixed frequency between a normal can and a poorly sealed can. Reference number 1 is the can body member, 2 is the bottom of the can, 3 is the side wall, 4 is the connection between the side wall and the bottom of the can, 5 is the flange, 6 is the can lid, 7 is the sealing part, and 8 is the protective resin coating. , 9 indicates a dome, and 10 indicates a neck, respectively.

Claims (1)

[Claims] 1 Formed by drawing and ironing a metal material,
The thickness of the trunk wall (Dd) is 0.10 to 0.14 mm, and the ratio of the thickness of the bottom wall (Db) to the thickness of the trunk wall (Dd) (Db/
Dd) is in the range of 1.5 to 2.2 and the internal pressure resistance is 3 kg/cm ² or more and less than 7 kg/cm ² ,
The feature is that an inert gas mainly composed of nitrogen is filled with a non-carbonated beverage, the can lid is sealed, and the resulting inert gas-filled can is inspected to detect a poorly sealed can. A manufacturing method for inert gas filled canning.