Note: Descriptions are shown in the official language in which they were submitted.
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PLASTIC CONTAINER HAVING CRIMP-ON, PRY-OFF CROWN FINISH
BACKGROUND
[0001] 7 . Technical Field - The present invention relates generally
to molded plastic containers, and particularly to injection-blow molded
bottles for containing carbonated beverages.
[0002] 2. General Background - For many years, glass bottles
have been formed with crown finishes; that is, with finishes specifically
designed to receive crimp-on, pry-off crown closures. Such closures are
low cost, easy to remove using a conventional bottle opener, and easy to
apply with the use of specially designed capping equipment. Over the
years, much capita! has been invested by bottlers of soft drinks and beer in
equipment for applying such crown closures to glass bottles that contain
their products. The character of glass contributes desirable properties that
help ensure that such closures are retained on the finish of the bottles even
in the presence of significant internal pressure presented by the
carbonation in the contained beverage. However, safety concerns based
on the frangibility of the glass have motivated some bottlers to consider the
use of plastic bottles instead of glass.
j0003] With the substitution of plastic for glass, there has also been
a commensurate substitution of a threaded closure for the crimp-on, pry-off
crown closure. Threaded closures provide a simple means for resealing an
opened bottle, which is particularly desirable for bottles containing volumes
of one liter or more. Threaded closures on single serving size bottles are
rarely used to reseal the contents. Threaded closures require the use of
different capping equipment than do the crown closures. In commercial
settings such as bars and restaurants, threaded closures are viewed as
undesirable on single serving containers. Thus, there is some motivation
to incorporate a finish suitable to receive a crimp-on, pry-off crown closure
onto plastic bottles. However, the more flexible characteristics of plastic do
not permit a mere substitution of a conventional crown finish as used in
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glass. Under testing, it has been determined that the mere substitution of a
conventional crown finish as used in glass results in insufficient retention
of
the crown cap. As a result, there is a need for a modified finish suitable to
receive a crimp-on, pry-off crown closure onto plastic bottles that will
retain
the crown closure satisfactorily even in the presence of significant internal
pressure generated by the carbonation in the contained beverage.
BRIEF SUMMARY
[0004] A plastic bottle of the present invention has a finish at the
bottle mouth that is generally symmetric about a vertical axis of the bottle,
which is suitable to receive a metal crown cap. The finish has a top
surface that includes a planar ring lying in a plane normal to the vertical
axis. A downwardly curved portion extends outward from the planar ring.
The downwardly curved outer portion terminates at an outermost edge
located at a radius R~ from the vertical axis of the bottle. The finish also
has an undercutting surface beginning adjacent to the outer edge and
extending axially inwardly and downwardly from the outer edge. The
undercutting surface can be considered as a concave partial toroidal
surface. The concave partial toroidal surface can be defined in substantial
part by a locus of points generated by a radius R having its origin on a
circle of radius R2 lying in a plane normal to the vertical axis, particularly
where R « R2 < R~. The concave partial toroidal surface interacts with a
conventionally applied metal crown cap in such a way as to retain the cap
under pressures that would cause cap leaking or expulsion with
conventional crown finishes.
[0005] The radius R defining the concave partial toroidal surface
must be less than about 15% of the radius R~, and is generally less than
10% of the radius R~. The length of radius R can even be less than about
7% of radius R~, and may be only about 4% of radius R~. The planar ring
on the top surface of the finish can have a width that is greater than about
2% of radius R~. The top surface can include a downwardly curved inner
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edge. The downwardly curved inner edge can be defined by a radius
having a length that is about equal to the width of the planar ring. The
downwardly curved inner edge generally terminates in a substantially
cylindrical inner surface of the bottle mouth defined by a radius R3. The
distance between the cylindrical inner surface of the bottle mouth and the
undercutting surface can be less than 25% R,, yet stilt retain sufficient
strength to permit the necessary pry-off function of a conventional metal
crown cap using a conventional bottle opener.
[0006] The various features and advantages of a bottle having a
crown finish of the present invention will become apparent to those skilled
in the art from a consideration of an illustrative embodiment shown in the
attached drawings and described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 is a perspective view of a bottle of the present
invention including a crown closure.
[0008] Figure 2 is a side elevation view of the neck and finish
portion of the bottle shown in Figure 1 including the crown closure in
greater detail.
[0009] Figure 3 is a sectional view of the finish portion of the bottle
shown in Figure 1 with the crown closure removed.
[0010] Figure 4 is a sectional detail view of the upper portion of the
finish showing the details of radii defining the surfaces of an example finish
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] A bottle 10 of the present invention is shown in Figure 1 to
include a base 12 that supports the bottle on any underlying surface. A
side wall 14 extends upward from the base 12. The side wall 14 typically
includes a label panel 16 adapted to receive a label, not shown, disclosing
the contents of the bottle 10. A shoulder 18 is located at the upper margin
of the label panel 16 the leads into a neck 20. The side wall 14, label
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panel 'i 6, shoulder 18 and neck 20 are generally rotationally symmetric
about a vertical axis Y projecting upward from base 12.
[0012] A finish 22 is located at the upper end of the neck 20 as
shown in Figures 1 and 2. The finish 22 is also generally symmetric about
the vertical axis Y and includes a support ring 24 extending outward from
the neck 20 to support the bottle 10, and the preform from which the bottle
is manufactured, not shown, during the manufacturing process, which is
typically a conventional one- or two-stage injection blow molding process.
A channel 26 separates the support ring 24 from a bell portion 28, which
has a bulbous lower portion 30 tapering inward as the bell portion 28 leads
upward toward a cap 32 that seals the bottle mouth.
[0013] The cap 32 is a conventional crown closure typically
manufactured of 0.235 mm single reduced, tin free steel. The cap 32
includes a central panel 34 surrounded by a depending skirt 36. The
skirt 36 is typically about 6mm in height and has an exposed lower edge 38
that is formed during the capping process to include a series of alternating
ribs 40 interspaced by flutes 42 extending around the entire lower edge 38.
A soft polymeric sealing material, not shown, is typically located on an
inner surface of the central panel 34 for sealing against a top surface of the
bottle 10, discussed below. The sealing material can be, for example,
made of PVC or other suitable flavor neutral polymer. The sealing
material, which is located on the inner surface of the central panel 34, is
maintained in contact with the top 44 surface of the bottle 10 by means of
strength of the inward projecting flutes 42 in cooperation with the structure
of the finish 22 described below.
[0014] The top surface 44 of the finish 22 is shown in Figures 3
and 4 to include a planar ring 46 lying in a plane normal to the bottle
vertical axis Y. A downwardly curved portion 48 extends outward from the
planar ring 46 to an outermost edge 50 located at a radius R~ from the
bottle vertical axis Y. An undercutting surface 52 begins adjacent to the
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outer edge 50 and extends radially inward and axially downward from the
outer edge 50. The undercutting surface 52 is a concave partial toroidal
surface defined in substantial part by a locus of points generated by a
radius R having its origin on a circle 54 of radius R2 lying in a plane normal
to the bottle vertical axis Y, where R2 is less than R~. The radius R
generating the undercutting surface 52 is very small as compared to either
radius R~ or R2. The length of radius R must be less than about 15% of the
radius R~, and is generally less than 10% of the radius R~. The length of
radius R can even be less than about 7% of radius R~, and may be only
about 4% of radius R~. The radius R2 of the circle 54 is smaller than the
outer radius R~, but can be nearly as big as radius R~. The radius R2 can
be as large as 97% of radius R~. A lower edge of the concave partial
toroidal undercutting surface 52 blends smoothly and generally tangentially
into the bell portion 28, which can be variously dimensioned both in height
and angle.
[0015] A downwardly curved inner edge 56 can be situated on the
inside of the planar ring 46. The downwardly curved inner edge 56
extends between the planar ring 46 and a cylindrical inner surface 58 of the
bottle mouth 60 defined by a radius R3. The radius R3 can be about 70%
to 80% of radius R,. The distance between the cylindrical inner surface 58
of the bottle mouth 60 and the undercutting surface 52 at the point of
closest approach can be less than 25% R~, but is generally greater than
about 15% R~. The distance between the inner edge 56 and the
downwardly curved outer portion 48 defines the width W of the planar
ring 46 as shown in Figure 4. The width of the planar ring 46 is preferably
greater than about 2% of radius R~.
[0016] The downwardly curved outer portion 48 can include a
plurality of blended radii R4;, R4;;, ... , that generally increase in size as
the
curved outer portion 48 proceeds from the planar ring 46 to the outermost
edge 50. The size of the radii R4;, R4;;, can vary between about 5% and
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15% of radius R,. A lower outside surface 62 of radius R5 can connect the
outermost edge 50 to the undercutting surface 52. The radius R5 is
preferably less than about 2% of radius R~.
[0017] The flutes 42 of the cap 32 engage the undercutting
surface 52 to retain the cap 32 in sealing engagement with the bottle
mouth 60 satisfactorily even in the presence of significant internal pressure
generated by the carbonation in the contained beverage. Further, the
strength provided by the material in the finish 22 permits the cap 32 to be
easily removed using a conventional bottle opener.
[0018] The foregoing detailed description should be regarded as
illustrative rather than limiting, and the following claims, including all
equivalents, are intended to define the spirit and scope of this invention.
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