Bottles and jars – Closures – Cap type
Reexamination Certificate
2001-02-08
2004-02-24
Newhouse, Nathan J. (Department: 3727)
Bottles and jars
Closures
Cap type
C215S354000, C215SDIG001
Reexamination Certificate
active
06695161
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a plastic container closure suitable for a container for a beverage, especially a container for a carbonated beverage.
DESCRIPTION OF THE PRIOR ART
A container formed from a plastic material, such as polyethylene terephthalate or glass, is widely used as a container for a beverage. Such a container includes a nearly cylindrical mouth-and-neck portion, and an external thread is formed on an outer peripheral surface of the mouth-and-neck portion. An upper end part of the mouth-and-neck portion, normally positioned above the external thread, has an annular top surface extending substantially horizontally, a cylindrical outer peripheral surface extending substantially vertically, and a cylindrical inner peripheral surface extending substantially vertically. The annular top surface and the cylindrical inner peripheral surface are connected together, substantially directly or via an annular boundary surface extending arcuately over a slight length in a sectional view. Similarly, an annular boundary surface, extending substantially arcuately over a considerable length in a sectional view, exists between the annular top surface and the cylindrical outer peripheral surface.
Recently, a plastic container closure formed from a plastic material, such as high density polyethylene or polypropylene, has found practical use as a container closure for sealing the mouth-and-neck portion of a container having the above-described shape. A typical example of such a plastic container closure has a circular top panel wall, and a cylindrical skirt wall extending downwardly from a peripheral edge of the top panel wall, as disclosed, for example, in Japanese Unexamined Patent Publication No. 73551/1983. An internal thread is formed on an inner peripheral surface of the skirt wall. An annular seal piece, which may extend downwardly obliquely in a radially inward direction, is formed in an outer peripheral edge portion of the inner surface of the top panel wall. An annular contact piece positioned radially inwardly of the annular seal piece, and an annular positioning piece extending downwardly at a position radially inward of the contact piece are also often formed in the outer peripheral edge portion of the inner surface of the top panel wall.
In mounting the container closure on the mouth-and-neck portion of the container to seal the mouth-and-neck portion, the container closure is capped over the mouth-and-neck portion, and turned in a closing direction to screw the internal thread of the container closure onto an external thread of the mouth-and-neck portion. During this motion, the annular positioning piece of the container closure is lowered along the inner peripheral surface of the upper end part of the mouth-and-neck portion. By this action, the container closure is aligned with the mouth-and-neck portion to match the center line of the container closure to the center line of the mouth-and-neck portion. When the internal thread of the container closure is screwed onto the external thread of the mouth-and-neck portion with a required rotating torque, the annular seal piece of the container closure is intimately contacted with the outer peripheral surface in the upper end part of the mouth-and-neck portion, whereby the mouth-and-neck portion is sealed. The contact piece of the container closure is brought into contact with the substantially horizontally extending top surface of the mouth-and-neck portion, whereby the vertical position of the container closure relative to the mouth-and-neck portion is restricted.
The conventional plastic container closure of the foregoing shape poses the following problem to be solved: Assume that a carbonated beverage containing a carbon dioxide gas is held in the container. When the ambient temperature reaches 40 degrees centigrade, for example, a considerably high gas pressure (e.g., a gas pressure of about 6 kg/cm
2
) is generated in the container. Such a gas pressure causes a so-called dome phenomenon in which the top panel wall of the container closure is deformed upward in a domic shape. As is well known among people skilled in the art, a container filled with a carbonated beverage and mounted with a container closure is usually accommodated in a carton (a box made of a folding boxboard). The cartons accommodating a required number of the containers are stored and transported in a stacked condition. During their storage and transportation, a considerable load (a load, for example, of about 10 kg) is imposed on the top panel wall of the container closure mounted on the mouth-and-neck portion of the container. According to experiments conducted by the inventors of the present invention, when a considerably great stacking load is imposed on the top panel wall of the container closure subject to the dome phenomenon, the seal on the mouth-and-neck portion by the container closure tends to be destroyed, resulting in leakage of the gas pressure from inside the container. To solve this problem, it is conceivable to form a sealing liner of a required shape on the inner surface of the top panel wall of the container closure, separately from the container closure body, by a well-known embossing method. By so doing, however, the manufacturing cost of the container closure is considerably increased.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide an improved plastic container closure which can be produced without an increase in the manufacturing cost, and which nevertheless, enables sealing of the mouth-and-neck portion by the container closure to be maintained fully reliably, even when a considerably great stacking load is imposed on the top panel wall of the container closure undergoing a dome phenomenon.
As a result of extensive studies and experiments, the inventors found the following facts, to their surprise: When the annular contact piece is changed to such a shape as to contact the annular boundary surface extending arcuately in the sectional view, rather than contacting the substantially horizontally extending top surface of the mouth-and-neck portion, sealing of the mouth-and-neck portion by the container closure can be maintained fully reliably, even if a considerably great stacking load is imposed on the top panel wall of the container closure when the above-mentioned dome phenomenon is caused to the top panel wall of the container closure. The reason why sealing of the mouth-and-neck portion can be maintained fully reliably by such a change applied to the annular contact piece of the container closure is not necessarily clear, but the inventors believe it to be as follows: Generally, when the dome phenomenon is caused to the top panel wall, the top panel wall is deformed upward in a region inward of the annular boundary surface of the mouth-and-neck portion. In other words, the top panel wall bulges upward more greatly in its region closer to its center, with the annular boundary surface of the mouth-and-neck portion as a fulcrum. If the annular contact piece of the container closure is in contact with the top surface inward of the annular boundary surface of the mouth-and-neck portion, the top panel wall is deformed, when a stacking load is imposed on the top panel wall undergoing the dome phenomenon. In accordance with this deformation, the annular contact piece is also deformed or moved. At the same time, the deformation of the top panel wall is transmitted to the annular seal piece. As a result, the annular seal piece is also deformed to destroy sealing of the mouth-and-neck portion. On the other hand, when the annular contact piece of the container closure is brought into contact with the annular boundary surface of the mouth-and-neck portion, namely, the fulcrum for the deformation of the top panel wall, the tendency toward the deformation or movement of the annular contact piece by the deformation of the top panel wall is considerably lessened. Moreover, the tendency to deformation of the annular seal piece due to the deformation of the top panel wall is considerably
Kaitsuka Yoshihiro
Kano Yuji
Japan Crown Cork Co. Ltd.
Newhouse Nathan J.
LandOfFree
Plastic container closure does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Plastic container closure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plastic container closure will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3327339