Synthetic resin container closure

Details Synthetic resin container closure Synthetic resin container closure

2001-03-13

2004-08-24

Newhouse, Nathan J. (Department: 3727)

Bottles and jars

Closures

Cap type

C215S354000, C215SDIG001, C215S252000

Reexamination Certificate

active

06779672

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a synthetic resin container closure formed from a synthetic resin material as a single unit and, more specifically, to a synthetic resin container closure which has a circular top panel wall and a cylindrical skirt wall extending downwardly from the peripheral edge of this top panel wall, one or two cylindrical sealing protrusions that extend downwardly being formed on the inner surface of the top panel wall.
DESCRIPTION OF THE PRIOR ART
A synthetic resin container closure which is wholly formed from an appropriate synthetic resin such as polypropylene or polyethylene as a single unit has been proposed as a container closure for drink or beverage containers and has been put to practical use. The container closure has a circular top panel wall and a cylindrical skirt wall extending downwardly from the peripheral edge of this top panel wall, and one or two cylindrical sealing protrusions extending downwardly are formed on the inner surface of the top panel wall. In a container closure disclosed in FIG. 3 of Japanese Unexamined Laid-Open Patent Publication 10-35699, two cylindrical protrusions, that is, an outer cylindrical protrusion and an inner cylindrical sealing protrusion both extending downwardly, are formed on the inner surface of the top panel wall. On the inner surface of the top panel wall is further formed an annular sealing ridge adjacent to the base portion of the outer cylindrical protrusion. The trade name of a product, the name of a manufacturer or distributor and the like are printed on the outer surface of the top panel wall by offset printing, for example. A female thread is formed on the inner peripheral surface of the skirt wall. This container closure is mounted on a container having a male thread formed on the outer peripheral surface of a mouth-neck portion. When the female thread of the container closure is screwed onto the male thread of the mouth-neck portion to mount the container closure on the mouth-neck portion, the inner cylindrical sealing protrusion is brought into close contact with the inner peripheral surface of the mouth-neck portion, and the annular sealing ridge is also brought into close contact with the boundary region between the outer peripheral surface and the top surface of the mouth-neck portion. The outer cylindrical protrusion is brought into not close contact, but relatively loose contact with the outer peripheral surface of the mouth-neck portion to assist close contact of the annular sealing ridge with the boundary region between the outer peripheral surface and the top surface of the mouth-neck portion.
However, the above container closure of the prior art involves the following problems to be solved. Firstly, in the above container closure of the prior art, it is necessary to fully and surely satisfy the basic requirement that when the container closure is mounted on the mouth-neck portion of the container, the mouth-neck portion is sealed hermetically without fail and when the mouth-neck portion is to be opened, appropriate torque is applied to the container closure to turn the container closure, without requiring excessive torque, so that the container closure can be removed from the mouth-neck portion. In addition, it is important that when the mouth-neck portion is to be opened, the sealing of the mouth-neck portion should be released after the container closure is turned at an angle larger than the required rotation angle. Describing this point in more detail, a weakening line is generally formed in the skirt wall of the container closure such that it extends in a circumferential direction, the skirt wall is divided into a main portion above the weakening line and a tamper-evident skirt portion below the weakening line, the above female thread is formed on the inner peripheral surface of the main portion, and an engaging means having an appropriate shape is formed on the inner peripheral surface of the tamper-evident skirt portion. When the container closure is mounted on the mouth-neck portion of the container, the engaging means is engaged with an engaging jaw portion formed on the outer peripheral surface of the mouth-neck portion. When the container closure is turned in an opening direction to open the mouth-neck portion of the container, the weakening line is at least partially broken, whereby the engagement of the engaging means with the engaging jaw portion is released, and the container closure is allowed to be removed from the mouth-neck portion. It is important that when the container closure is turned in the opening direction, the sealing of the mouth-neck portion should be released after the weakening line is at least partially broken. If the sealing of the mouth-neck portion is released before the weakening line is at least partially broken, there occurs such a situation that though the container closure has been tampered to be turned in the opening direction and the sealing of the mouth-neck portion has been released, the weakening line is not broken, and accordingly an indication that the container closure has been tampered and the sealing of the mouth-neck portion has been released does not remain. Therefore, in the above container closure of the prior art, there is a tendency that the sealing of the mouth-neck portion is released before the container closure is turned at a predetermined rotation angle owing to the production tolerance of the container closure and/or the mouth-neck portion or owing to the thermal deformation of the container closure and/or the mouth-neck portion, and there may occur a case where the above basic requirement can not be satisfied.
Secondly, the above container closure is formed from an appropriate synthetic resin by compression molding or injection molding. The molding efficiency of the molding step greatly depends on the required cooling time in the mold, as is well known to people having ordinary skill in the art. When the molded container closure is removed from the mold before the passage of the required cooling time, deformation greater than the permissible range may occur in the circular top panel wall. More specifically, there is a tendency for the center of the top panel wall to be indented, and consequently the top panel wall has a depressed shape more than the permissible range. To shorten the required cooling time without causing deformation greater than the permissible range in the top panel wall, it is known for the thickness of the top panel wall, particularly the center portion positioned on the inner side of the inner cylindrical sealing protrusion, to be reduced to promote the cooling of the top panel wall, particularly the center portion thereof. However, when the thickness of the top panel wall, particularly the center portion thereof, is reduced, another problem arises as follows. When the outer surface of the top panel wall is to be printed, the container closure is mounted on a mandrel to contact the top surface of the mandrel to the inner surface of the center portion of the top panel wall, and then an offset printing roller made from a material having elasticity, such as synthetic rubber, is applied to the outer surface of the top panel wall of the container closure in a printing area. Even when the outer surface of the top panel wall has some distortion of ordinary permissible degree, it is important for carrying out fully satisfactory printing that the printing roller should be compressed by approximately 1 mm when the printing roller is applied to the outer surface of the top panel wall of the container closure. In this case, when the thickness of the top panel wall is reduced to 1 mm for example, the space between the peripheral surface of the printing roller and the top surface of the mandrel to which the container closure is not mounted must be set to substantially zero. In a case of the setting being made like this, if the mandrel is moved through the printing area without the container closure mounted thereon for some accidental reason, printing ink will be adhered to the top surface of

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