US20060151423A1 - Closure having tapered sealing plug - Google Patents

A plastic closure for a container includes an upper wall and a generally cylindrical sidewall that depends downwardly from the upper wall: The generally cylindrical sidewall has a threaded internal surface so that it may be screwed onto a container neck. The closure further includes an annular sealing plug that depends downwardly from a lower surface of the upper wall. The annular sealing plug has an inner annular surface that when viewed in longitudinal cross-section extends at a first angle with respect to a longitudinal axis of said closure and an outer annular surface that when viewed in longitudinal cross-section extends at a second angle with respect to the longitudinal axis. The first angle is advantageously greater than the second angle, creating a tapered profile that improves moldability of the closure.

BACKGROUND OF THE INVENTION

• 1. Field of the Invention

• This invention relates to a plastic closure suitable for sealing a container, such as a container for a carbonated beverage.

• 2. Description of the Related Technology

• Most carbonated beverages are conventionally packaged within a container that is either formed from glass or a plastic material such as polyethylene terephthalate and that includes a substantially cylindrical finish portion having an external thread formed on an outer peripheral surface thereof. The finish portion typically 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 intersect each other either at a discrete edge or via an annular boundary surface that extends arcuately over a slight distance as visualized within a longitudinal cross-sectional view. Similarly, an annular boundary surface, extending substantially arcuately over a considerable length in a longitudinal cross-sectional view, exists between the annular top surface and the cylindrical outer peripheral surface.

• It is also conventional to provide a plastic container closure for non-carbonated beverages that is screwable onto the finish portion in order to seal the container. Such closures are typically formed from a plastic material, such as high density polyethylene or polypropylene. A typical example of such a 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 U.S. Pat. No. 4,564,112 to Breuer. An internal thread is formed on an inner peripheral surface of the skirt wall. An annular sealing plug depends downwardly from the inner surface of the top panel 1, wall. This annular sealing plug has an outer circumferential surface that is adapted to seal against the cylindrical inner peripheral surface of the finish portion of the container when the closure is screwed onto the container.

• Unfortunately, it is often problematic to mold effective annular sealing plugs because of difficulty of ejecting the molded plug from the mold after fabrication.

• In many conventional closure designs, a lining material must be inserted into the closure in a secondary operation in order to provide an effective seal. This adds substantially to the cost of manufacturing the closure and furthermore adds to the weight of the closure.

• A need exists for an improved single piece closure having a sealing plug that can be easily fabricated and that does not require insertion of a lining material after molding.

SUMMARY OF THE INVENTION

• Accordingly, it is an object of the invention to provide an improved single piece closure having a sealing plug that can be easily fabricated and that does not require insertion of a lining material after molding. It is further an object of the invention to provide such a closure that is suitable for use with containers for carbonated beverages.

• In order to achieve the above and other objects of the invention, a plastic closure for a container according to a first aspect of the invention includes an upper wall; a generally cylindrical sidewall depending downwardly from the upper wall, the sidewall having a threaded internal surface; and an annular sealing plug depending downwardly from a lower surface of the upper wall, the annular sealing plug having an inner annular surface that when viewed in longitudinal cross-section extends at a first angle with respect to a longitudinal axis of the closure and an outer annular surface that when viewed in longitudinal cross-section extends at a second angle with respect to the longitudinal axis, and wherein the first angle is greater than the second angle.

• According to a second aspect of the invention, a method of packaging a carbonated beverage includes steps of filling a container with a carbonated beverage; and sealing the container by applying a plastic closure having an upper wall; a generally cylindrical sidewall depending downwardly from the upper wall, the sidewall having a threaded internal surface; and an annular sealing plug depending downwardly from a lower surface of the upper wall, the annular sealing plug having an inner annular surface that when viewed in longitudinal cross-section extends at a first angle with respect to a longitudinal axis of the closure and an outer annular surface that when viewed in longitudinal cross-section-extends at a second angle with respect to the longitudinal axis, and wherein the first angle is greater than second angle.

• These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1

  is a diagrammatical cross-sectional view depicting a closure that is constructed according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

• Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to

  FIG. 1

  , a

  plastic closure

  10 for a

  container

  12 includes an

  upper wall

  13 that is generally circular in shape as viewed from above or below and a generally cylindrical downwardly depending

  sidewall

  14 that is unitary with the

  upper wall

  13 and that depends downwardly to form a skirt or apron. Closure 10 is preferably fabricated from an appropriate plastic material such as high density polyethylene or polypropylene.

  Upper wall

  13 and

  sidewall

  14 are preferably constructed of sufficient thickness to resist significant distortion as a result of forces that are exerted on the

  closure

  10 by the pressurization created by a carbonated beverage.

• Closure 10 further includes in the preferred embodiment a tamper-

  evident band

  16 that is frangibly attached to the

  sidewall

  14 and that includes a

  retention hook

  18 that is designed to engage structure on the

  container

  12 in order to cause separation between the

  sidewall

  14 and the tamper-

  evident band

  16 upon removal of the

  closure

  10 from the

  container

  12 by a consumer.

  Sidewall

  14 is provided with a plurality of

  internal threads

  20 that are constructed and arranged to interengage with complementary threads that are formed on the outer peripheral surface of the finish portion of the

  container

  12. This permits the

  closure

  10 to be screwed onto and off of the

  container

  12.

• Referring again to

  FIG. 1

  ,

  closure

  10 further includes an advantageously constructed annular sealing plug 22 that is unitary with and depends downwardly from the

  lower surface

  24 of the

  upper wall

  13. Annular sealing plug 22 preferably is substantially symmetrical about the longitudinal axis of the

  closure

  10, meaning that the profile of the annular sealing plug 22 that is provided in the cross-sectional view of

  FIG. 1

  would be substantially identical in any other possible longitudinal cross-sectional view of the

  closure

  10. Annular sealing plug 22 has an inner

  annular surface

  26 that includes a

  linear portion

  28 as viewed in

  FIG. 1

  that extends for substantially the entire length of the inner

  annular surface

  26 and that intersects with the

  lower surface

  24 of the

  upper wall

  13.

  Linear portion

  28 is angled downwardly and outwardly toward the

  sidewall

  14 at a first angle Θ with respect to a vertical line that is parallel to the longitudinal axis of the

  closure

  10. Preferably, this first angle Θ is at least 2°, is more preferably at least 10° and is most preferably at least 15°. In the most preferred embodiment, this first angle Θ is approximately 17°.

• While

  portions

  28, 32 have been described as linear, it will be visualized that the true shape of the surfaces is substantially frustoconical.

• Annular sealing plug 22 further preferably has an outer

  annular surface

  30 that includes a

  linear portion

  32 as viewed in longitudinal cross-section that extends for most of the length of the annular

  outer surface

  30 including the intersection of the annular

  outer surface

  30 and the

  lower surface

  24 of the

  upper wall

  13.

  Linear portion

  32 defines a second angle q) with respect to a vertical line that is parallel to the longitudinal axis of the

  closure

  10. According to one important aspect of the invention, the first angle Θ is greater than the second angle Φ so as to downwardly taper substantially the entire body of the annular sealing plug 22. This has been determined to make the

  closure

  10 easier to mold, particularly in the area about the annular sealing plug 22. Preferably, the first angle Θ is greater than the second angle Φ by at least 2°. The second angle Φ could range from 0° upwards, as long as it is smaller than the first angle Θ.

• Preferably, the annular sealing plug 22 further includes an annular radiused

  end portion

  34 that intersects the outer

  annular surface

  30 at a smooth feathered radius, and that intersects the inner

  annular surface

  26 at a

  lower edge

  36.

• The invention also encompasses a method of packaging a carbonated beverage that is performed by inserting a carbonated beverage into a container and subsequently sealing the container using the

  closure

  10 described above.

• It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.