Package making – Methods – With contents treating
Reexamination Certificate
2000-10-17
2003-02-18
Rada, Rinaldi I. (Department: 3721)
Package making
Methods
With contents treating
C053S432000, C141S082000, C141S103000
Reexamination Certificate
active
06519919
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method and apparatus for manufacturing a gas displacement pressurized packaging body in containers such as cans for canned goods, molded containers, plastic bottles, and glass bottles, etc., and more particularly to a method and apparatus for manufacturing a pressurized packaging body wherewith the inert gas displacement ratio can be increased, container internal pressures can be stably obtained that are suitable positive pressures, small volume injecting of a liquid inert gas can be done with high precision, and low pressurized packaging bodies can be obtained which exhibit outstanding guaranteed quality.
BACKGROUND ART
Conventionally, in manufacturing canned goods, a pressurized canned goods manufacturing method is commonly employed wherein the head space of the can is injected with an inert gas (which is ordinarily liquid nitrogen and therefore hereinafter represented by liquid nitrogen) that is made to flow down while the can is being conveyed from the filler to the seamer, and the can is seamed and sealed while the vaporizing expansion of the liquid nitrogen is continuing, whereby an internal pressure is produced by the vaporizing expansion of remaining liquid nitrogen after sealing. The main objective in injecting the liquid nitrogen and causing a positive pressure to be generated in the can is to give rigidity to the can by the positive pressure, thus making it possible to use thinner walled materials for the can and to reduce the amount of material used. Moreover, by displacing the gas (air) inside the can with nitrogen (inert gas) and removing the oxygen, the benefit of preventing flavor deterioration due to oxidation of the contents is also gained. Another objective is to aggressively make the pressure inside the can either positive or negative, and then perform an inspection to determine whether the pressure inside the can is being held at a prescribed pressure or not, thereby making it possible to detect leakage of the canned goods and spoilage in the contents due to bacterial incursion, and hence to guarantee that the contents are safe.
However, with the conventional method wherein liquid nitrogen is sealed in and an internal pressure is produced, there is a drawback that fluctuation of the injected liquid nitrogen volume is significant and the prescribed internal pressure can not be stably obtained, particularly because the liquid nitrogen splashes out to the outside of the can during liquid nitrogen injection and during lid seaming. For that reason, there is a problem that the material used for the can cannot be made thin to the limit of what can withstand the prescribed internal pressure, and the quantity of material used cannot be reduced effectively. When a small volume of liquid nitrogen is injected, in order to obtain low internal pressure cans, the fluctuation relative to the target injecting volume becomes significantly larger, wherefore it has not been possible to stably obtain low pressurized cans by injecting small volumes of liquid nitrogen with the conventional liquid nitrogen injection method. In the case of easily spoilable liquid content such as beverages containing milk, vacuum cans or low pressurized cans are demanded wherewith it is easy to detect swelling caused by microorganisms. However, when the internal pressure fluctuation is significant as described above, it can no longer be determined whether swelling is caused by microorganisms or by fluctuation in internal pressure resulting from liquid nitrogen injection. For that reason, until now, the easily spoilable liquid content have had to fill with thick walled cans because means for enhancing can strength by producing a pressure inside the cans by injecting liquid nitrogen could not be employed.
Furthermore, with the conventional liquid nitrogen injection method, internal pressure fluctuation in pressurized cans also happens as a result of the fluctuation in the amount of filling contents. That is, even supposing that the definite volume of liquid nitrogen remains, when the volume of filling contents increases (that is, the head space decreases), the internal pressure increases due to vaporizing expansion of the liquid nitrogen. Therefore, in order to obtain accurate internal pressure, the liquid nitrogen injection volume must be controlled according to the fluctuation of the filling content volume. It has been impossible to achieve this with the conventional method.
It has also been proposed that the liquid nitrogen be atomized and then injected (Japanese Patent Publication No. S59-9409/1984). However, unlike with ordinary liquids having a high boiling point, liquid nitrogen that have a boiling point of −196° C. at atmospheric pressure and vaporizes very easily, atomization cannot be done stably even when it is sprayed under pressure, wherefore this method has not yet been made practical. The cause for this is that, when liquid nitrogen is sprayed to the atmosphere, the liquid nitrogen is heated and vaporized by the atmosphere at room temperature, whereupon vaporization occurs in the spray nozzle prior to atomization, causing pressure fluctuations and foam gripping at the spray orifice, which causes pulsation. In particular, when spraying is done under high pressure, the boiling point decreasing when the liquid nitrogen is passing through the spray nozzle becomes large, the liquid nitrogen boils inside the nozzle, pulsation occurring, whereupon fine particles cannot be stably obtained. Another cause is that the moisture contained in the atmosphere freezes at the nozzle tip, blocking the spray orifice and resulting in unstable spray volume. Even assuming that stable atomization can be effected, the filling accuracy of the fine particles of liquid nitrogen injected in the container will be poor unless the injected liquid nitrogen spray pattern is consistent with the direction of conveyance. Particularly in the case of a high speed filling line, the fine particles of liquid nitrogen may splash back when colliding the surface of the liquid content so that they splash out of the container. Thus this method still does not satisfy to obtain low pressurized cans that requires the small volume injection of liquid nitrogen with extremely high accuracy.
Therefore, an object of the present invention is to provide a method and apparatus for manufacturing a pressurized packaging body wherewith prescribed internal pressures of the pressurized packaging bodies can be stably obtained even at low internal pressure by increasing the accuracy of the initial internal pressure, and the inert gas displacement ratio in the pressurized packaging bodies can be dramatically improved over the prior art.
A detailed object of the present invention is to provide a method and apparatus for manufacturing a pressurized packaging body, wherewith small volume injection of liquefied inert gas or solidified inert gas can be done precisely by stably made into fine particles, wherewith low pressurized gas displacement packaging bodies are obtained which exhibit outstanding guaranteed quality, and wherewith it is possible to employ thin walled cans even for cans containing low acid beverages.
DISCLOSURE OF THE INVENTION
The present invention, basically, is a method wherewith a liquefied inert gas or solidified inert gas that is to be vaporized to become an inert gas is made into fine particles, sprayed together with a low temperature inert gas having a temperature that is at or below the final equilibrium temperature of the gas displacement pressurized packaging body into the head space of a container filled with contents, and sealed, thereby displacing the gas in the head space with the inert gas, and, at the same time, causing an internal pressure to be produced both by the vaporizing expansion of the fine particles of the remaining liquefied inert gas or the fine particles of the remaining solidified inert gas, and also by the thermal expansion of the said low temperature inert gas, after sealing. Thus it is possible to obtain pressurized packaging bodies that exhibit high int
Iwasaki Tsutomu
Kimura Yoshihiko
Koike Hidetoshi
Kurosawa Kazuyuki
Senbon Katsumi
Rada Rinaldi I.
Rader & Fishman & Grauer, PLLC
Toyo Seikan Kaisha Ltd.
Tran Louis
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