US20090008360A1

US20090008360A1 - Finish and closure for plastic pasteurizable container

Info

Publication number: US20090008360A1
Application number: US11/756,186
Authority: US
Inventors: David P. Piccioli; Amit S. Agrawal; Wayne N. Collette
Original assignee: Graham Packaging Co LP
Current assignee: Graham Packaging Co LP
Priority date: 2007-05-31
Filing date: 2007-05-31
Publication date: 2009-01-08
Also published as: BRPI0812025A2; WO2008148124A2; WO2008150823A1; EP2155573A1; WO2008148124A3; MX2009012681A; AU2008260196A1

Abstract

Plastic containers subjected to pasteurization processes with a closure having an annular finish support ring that supports an inner surface of the neck finish of the container from inward deformation during pasteurization. The finish support ring can be integral with the closure or can extend from a closure liner. Also disclosed are closures for products that require pasteurization, as well as modified finish threads to provide a surface contact between the finish and closure threads.

Description

FIELD OF THE INVENTION

The present invention relates to plastic container finish and closure systems that are subjected to pasteurization processes.

BACKGROUND OF THE INVENTION

Many products require pasteurization to reduce the number of microorganisms that may be present in the product (e.g., food or beverage) during packaging and that can degrade the product. One known pasteurization process is performed after the containers are filled with product and sealed, and involves gradually elevating the temperature of the filled and sealed containers to a desired temperature (e.g., 140° F. for beer), where it is held for a period of time. The container and its contents are then cooled to ambient temperatures where the containers can be labeled, packaged, and stored. Products that are typically pasteurized include fruit juices, milk, and beer.
Although products such as beer have historically been pasteurized in glass bottles, it would be desirable to use plastic containers, e.g., containers comprising polyethylene terephthalate (PET) for products requiring pasteurization. Because a container experiences a range of temperatures during pasteurization, these conditions can cause a plastic container to undergo permanent, uncontrolled deformation. Accordingly, there remains a need to provide plastic containers that can withstand pasteurization with a minimum of deformation.
It is known to crystallize the neck finish of a plastic container for purposes of increasing its thermal stability. Thus, it is known to provide a thermally crystallized PET container finish to prevent distortion of the neck finish during pasteurization. However, there is a significant increase in cost involved in crystallizing the finish in order to prevent distortion. It would thus be desirable to provide a pasteurizable package which does not require crystallization of the container neck finish.

SUMMARY OF THE INVENTION

In accordance with various embodiments of the invention disclosed herein, there is provided a plastic closure for supporting an amorphous neck finish of a pasteurizable plastic container against deformation. This closure can be used to minimize the finish distortions which normally occur at the high temperatures and pressures involved in the pasteurization process, and as a result, prevent any significant loss of pressure and/or product leakage.
In further embodiments, the closure can be provided with a liner to enhance seal integrity. Still further, the one or more threads on the container neck finish can be modified to increase the surface contact between the container thread and closure thread, for example, by providing complementary planar thread profiles on the container and closure threads, which provide surface contact and support features. Alternatively, or in addition, one can modify the angle and/or depth of a thread for a greater resistance to deformation. Still further, the container thread may be thickened to further prevent deformation. For example, an increased depth of the container thread, or contact at a region that takes advantage of the greater thread thickness closer to the neck finish wall can be used to withstand the conditions of pasteurization without loss of seal integrity.
In a further embodiment, a nonvented closure thread is provided so as to prevent nonuniform deformation of the container thread during pasteurization.
In accordance with one embodiment of the invention, disclosed herein is a plastic closure for supporting an amorphous neck finish of a pasteurizable plastic container against deformation, comprising:

- a top wall;
- a depending annular skirt extending from the top wall; and
- a rigid finish support ring extending from the top wall, the finish support ring having an outer diameter sized to support an inner diameter of the amorphous container neck finish against inward deformation during pasteurization.

Another embodiment provides a plastic closure for supporting an amorphous neck finish of a pasteurizable plastic container against deformation, comprising:

- a shell comprising a top wall and a depending annular skirt extending from the top wall;
- a liner covering at least a portion of the underside of the top wall; and
- a rigid finish support ring extending from the liner, the finish support ring having an outer diameter sized to support an inner diameter of the amorphous container neck finish against inward deformation during pasteurization.

Another embodiment provides a pasteurizable package comprising:

- a pasteurizable plastic container having an amorphous neck finish; and
- a plastic closure comprising a depending annular skirt extending from a top wall and a rigid finish support ring extending from the top wall, the finish support ring having an outer diameter sized to support an inner diameter of the neck finish against inward deformation during pasteurization.

Another embodiment provides a pasteurizable package comprising:

- a plastic pasteurizable container comprising an amorphous neck finish having a vented thread; and
- a plastic closure comprising a top wall and a depending annular skirt, an inner wall of the skirt having a nonvented thread that engages the vented thread of the neck finish,
- wherein the nonvented closure thread has a planar surface that contacts a planar surface of the vented container thread to provide substantially planar surface contact between the closure thread and the container thread and to support the container thread against deformation during pasteurization.

Another embodiment provides a pasteurizable package comprising:

- a plastic pasteurizable container comprising an amorphous neck finish having a thread; and
- a plastic closure comprising a top wall and a depending annular skirt, an inner wall of the skirt having a thread that engages the thread of the neck finish,
- wherein the container thread contacts the closure thread at a distance of at least 50% of the radial depth of the thread, as measured from the tip of the thread to a wall of the neck finish, to support the container thread against deformation during pasteurization.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will be understood from the following description, the appended claims and the accompanying drawings, in which:

FIG. 1 is a schematic view of a pasteurization tunnel;

FIG. 2A is a sectional view of a finish capped with a closure prior to heating;

FIG. 2B is a sectional view of the capped finish of FIG. 2A that has been heated to pasteurization temperatures;

FIG. 2C is a sectional view of the capped finish of FIG. 2B that has been subsequently cooled;

FIG. 3 is a sectional view of a container capped with a closure having a finish support ring;

FIG. 4 is a sectional view of a container capped with a closure having a liner with a finish support ring;

FIG. 5 is a sectional view of a container capped with a closure having a finish support ring and additional oxygen barrier and/or oxygen scavenging inner liner;

FIG. 6 is a sectional view of a container capped with a closure having a finish support ring and additional oxygen barrier and/or oxygen scavenging outer liner;

FIG. 7 shows a container neck finish with deformed threads;

FIG. 8A is a detailed sectional view of a bottle thread having point contact with a closure thread;

FIG. 8B is a detailed sectional view of bottle and closure threads having surface contact;

FIG. 8C is a detailed sectional view of a finish thread modified to have an additional thickness;

FIG. 8D is a detailed sectional view of a finish thread contacting a bottle thread at the midpoint region of the finish thread;

FIG. 8E is a detailed sectional view of a finish thread contacting a bottle thread at a region of the finish thread closer to the finish wall; and

FIG. 9 schematically depicts a device for applying a predetermined amount of force to a neck finish.

DETAILED DESCRIPTION

Disclosed herein are plastic container packages for products that require pasteurization.
The pasteurization process has been mechanized and automated for mass packaging. A typical pasteurization apparatus is a tunnel pasteurizer, such as those described in U.S. Pat. Nos. 2,282,187, 4,441,406, and 4,693,902, the disclosures of which are incorporated herein by reference. FIG. 1 schematically shows a system 1 that includes apparatus and processes for the manufacture, filling and pasteurization of a filled plastic container 8 in a pasteurization tunnel 2. System 1 includes a conveyer belt 3 for conveying the containers through stations for filling, capping, and pasteurization processes. A central longitudinal axis A of the container 8 is shown in FIG. 1 and serves throughout this specification as a reference point of orientation (e.g., radially outward from axis A).
In FIG. 1, container 8 is manufactured in blow mold 6 and downstream from blow mold 6 (in the direction indicated by the arrows) container 8 is carried by conveyer belt 3 to zone 10 for filling with the contents to be pasteurized, to zone 12 for sealing with a closure 9, and finally to the pasteurization tunnel 2 through tunnel entrance 4. In tunnel 2, various heating and cooling zones progressively raise and subsequently lower the temperature of the filled and sealed container. These heating/cooling zones comprise a series of showers each having a predetermined temperature. In tunnel 2, container 8 is first wetted by a first set of showers in zone 14 to gradually increase the temperature of container 8 and its contents. FIG. 1 schematically shows only one set of showers in each of zones 14, 16, and 18, although the number can vary to two or more depending on the desired rate of temperature change, and/or length of time to maintain the bottle at a desired temperature. Subsequently, shower(s) in zone 16 maintain bottle 8 at a pasteurization temperature, e.g., 140° F. for beer. The container 8 is then conveyed to zone 18 where shower(s) cool the bottle 8 down to ambient temperature. A precooling liquid in zone 18 may be at a temperature of 125° F., optionally followed by successive cooling sprays at for example 75° F. and 60° F. Bottle 8 emerges from the pasteurization tunnel 2 through exit 5 at a desired temperature with the pasteurized product ready for labeling and distribution.
The conveyer belt can have the design of U.S. Pat. No. 2,658,608, the disclosure of which is incorporated herein by reference. Alternatively, the method of conveyance can involve a walking beam as described in U.S. Pat. No. 4,441,406, the disclosure of which is incorporated herein by reference. One of ordinary skill in the art would readily appreciate that the blow molding, filling, capping and/or conveying processes do not necessarily occur in or with the same apparatus as that used for pasteurization and can be performed with a different apparatus.
Tunnel 2 of FIG. 1 illustrates one embodiment of a pasteurization system. However, it will be apparent to those skilled in the art that different forms of apparatus may be employed to carry out the pasteurization process, and the various parameters of the process (e.g., time and temperatures of the liquid sprayed on the containers) may be varied in accordance with the nature of the product to be treated and the results desired. For example, FIG. 1 depicts three heating and cooling zones, although any number of spray systems can be used as known in the art, e.g., more zones can be used and each zone can comprise one or more showers using any number of designs known in the art.
Due to the range of temperatures experienced by the container during pasteurization (e.g., from room temperature to 140° F.), plastic containers enclosing products that require pasteurization can experience deformations in the neck finish. An example of such neck deformation is illustrated schematically in FIGS. 2A-2C. FIG. 2A shows a sectional view of a neck finish 30 capped with closure 40 prior to pasteurization. Closure 40 comprises top wall 42 and a depending skirt 44 extending from the perimeter of wall 42. Threads 46 line the inner diameter of skirt 44, and engage complementary outer threads 36 of neck finish 30. Closure 40 may optionally have a liner 48 that covers the underside of top wall 42 to provide an additional seal.
During the heating phase of pasteurization, the liquid product and head space gases expand within the sealed container. For example, when a container is filled with beer, the pressure can increase from, e.g., 15 psi while cold (if the container is cold-filled with beer at e.g. 35° F.) to approximately 45 psi at ambient temperature (75° F.), and can peak at approximately 85 psi at a pasteurization temperature of 140° F. Other products may experience different pressure changes. At these higher pressures, the gas expansion can cause top wall 42 of closure 40 to dome upward in the direction of arrow 31, as shown in FIG. 2B. This doming applies an inward force at an upper portion of skirt 44 in the approximate direction of arrows 32, resulting in movement of the upper end of the bottle neck inward, as indicated by deformed region 37. After the bottle cools, as shown in FIG. 2C, the closure 40 relaxes back to its original formation. However, the upper neck finish at 37 remains in its inward deformed condition, indicated by the solid lines (dotted lines indicate the original shape of the neck finish).
Neck finish deformations, such as that described above, can affect the integrity of the product (e.g., loss of carbonation pressure, exposure to oxygen, leakage of product). For example, the seal between the neck finish and closure can be compromised by the doming, as the contact between the neck and liner and/or the neck and closure engagement threads can be reduced due to the deformed neck.
Accordingly, one embodiment provides a plastic closure for engaging a neck finish of a container. The plastic closure is capable of supporting an inner diameter of the container neck to substantially prevent permanent inward deformation of the neck caused by the pasteurization process.
FIG. 3 shows one embodiment of a closure of the present invention. A neck finish 30 is capped by a closure 50 having a top wall 52 and an annular skirt 54 extending from the perimeter of top wall 52. An inner diameter of skirt 54 has inner threads 56 that engage complementary outer threads 36 of neck finish 30. A rigid integral finish support ring 53 also extends from top wall 52, where the finish support ring 53 has an outer diameter 55 less than the inner diameter of the annular skirt 54. Specifically, the outer diameter 55 of finish support ring 53 has a dimension that allows the finish support ring 53 to engage and thus support an inner diameter 33 of the container neck finish 30 against inward deformation, e.g., of the type illustrated in FIGS. 2B and 2C; the outer diameter 55 is thus substantially equal to (may be slightly less than) the inner diameter 33 of neck finish 30. In one embodiment, finish support ring 53 sealingly engages inner diameter 33 of neck finish 30. Moreover, finish support ring 53 has sufficient rigidity, based on material, and dimensions, e.g., to support inner diameter 33, and thus the neck finish 30, to substantially prevent inward deformation. In one embodiment, the dimensions of the finish support ring are determined based on at least one of the finish support ring thickness and length, e.g., the length the finish support ring extends into finish, where the length of the finish support ring can be measured from the underside 58 of top wall 52 of the closure 50 to the bottom end of the finish support ring 53 (see FIG. 3).
The bottle can comprise a polyester, such as polyethylene terephthalate, either as a single layer or multi-layer incorporating other resins, such as polyamides, polyolefins, polyvinylidene chloride (PVDC) and ethylene vinyl alcohol (EVOH). The closure can be made of polyolefins, such as polyethylene (high or low density), polypropylene, or copolymers thereof. For example, the closure can be a compression-molded polypropylene cap able to withstand the pasteurization process without deformation.
FIG. 3 depicts finish support ring 53 as an integral portion of closure 50. Alternatively, a solid plug (extending across the full inner diameter of the neck finish) can be provided in place of finish support ring 53, the plug having the same outer diameter as finish support ring 53. Other designs can be envisioned by one of ordinary skill in the art to support inner diameter 33 of the neck finish 30.
FIG. 4 shows another embodiment of a closure of the present invention where the finish support ring is not integral with the closure. Closure 70 comprises top wall 72 and depending skirt 74. Closure 70 has threads 76 around an inner diameter of skirt 74 to engage complementary threads 36 of neck finish 30. Instead of the integral finish support ring of FIG. 3, a plastic liner 71 in FIG. 4 covers the underside of top wall 72. A rigid finish support ring 73 extends from liner 71 where the outer diameter 75 of finish support ring 73 is substantially equal to (may be slightly less than) the inner diameter 33 of neck finish 30. As with the finish support ring 53 of FIG. 3, finish support ring 73 of FIG. 4 has suitable dimensions and rigidity to support inner diameter 33 of neck finish 30 from inward deformation during pasteurization.
The liner may cover the entire underside of top wall 72, as shown in FIG. 4, or alternatively, cover only the portion of wall 72 that contacts rim 35 of neck finish 30. The liner can be made of the same materials as the closure, e.g. a rigid plastic such as a polyolefin, or can be made from a material different from that of the closure.
Depending on the product, the closure of the invention can include a liner made from a gas barrier material, e.g., an oxygen barrier material, including one or both of passive and active barrier materials. FIG. 5 shows the closure of FIG. 3 containing in addition a liner 51 covering the underside of the top wall 52 over the area defined by the inner wall of finish support ring 53. Exemplary active barrier materials include oxygen scavenging materials, such as those disclosed in U.S. Pat. Pub. No. 2004/0043172. Exemplary passive barrier materials include those chosen from elastomers, plastisol, polyolefins, ethylene vinyl acetate (EVA), ethylene vinyl alcohol (EVOH), polyvinyl alcohol (PVOH), polyvinyldene chloride (PVDC), polyethylene naphthalate (PEN), polyacrylonitrile (PAN), styrene acrylonitrile (SAN), liquid crystal polymer (LCP).
Alternatively, or in addition to liner 51, FIG. 6 shows the closure 50 of FIG. 3 further comprising an outer annular liner 57 comprising an active oxygen scavenging material or a passive oxygen barrier material, such as those disclosed herein. Annular liner 57 extends outwardly from the outer diameter 55 of finish support ring 53 to the inner diameter of skirt 54 to provide a seal against rim 35 of neck finish. Optionally, annular liner 57 can extend over only a portion of closure 50 that would contact rim 35 of neck finish 30.
Liners 51 and/or 57 of FIGS. 5 and 6, respectively, can also be incorporated in the closure 70 of FIG. 4. Liners 51 and/or 57 can cover the underside of liner 71 in the same manner that it would cover the underside of top wail 52 of closure 50 (FIG. 3).
In addition to affecting the shape of neck finish 30, the deformations from pasteurization can also affect the integrity of the finish threads 36. For example, where the threads of the closure are vented, e.g., segmented (not continuous) in a manner to allow a pathway to relieve excess pressure, the doming of the closure and accompanying inward deformation of the neck finish during heating, as shown in FIG. 2B, can cause the neck finish threads and segmented closure threads to push against each other. FIG. 7 shows a perspective view of a neck finish 80 having continuous finish threads 82 after the neck finish was subjected to pasteurization utilizing a closure with segmented closure threads. The resulting finish threads 82 have intermittent bends or deformations 84 from pressure contact with the segmented closure threads. The ratchet-type deformation of the neck finish threads makes removal of the closure more difficult and may otherwise be undesirable (e.g., produce a clicking sound) from a customer (user) perspective. Also, as the threads are displaced upwards, the seal in contact with the bottle becomes compromised.
Accordingly, one embodiment provides a closure having nonvented (continuous, non-segmented) threads that engage complementary threads of the neck finish. If finish thread deformation occurs due to contact between the closure and neck finish threads, the continuous closure threads will cause a more even deformation of the neck finish threads and thus substantially eliminate the formation of segmented bends or ratchet-type deformations of the neck finish threads.
In another embodiment, the threads of the neck finish and closure are vented. Vented finish threads may be desirable for use with pressurized products such as carbonated beverages (e.g., water, soda, and beer).
Another embodiment of a bottle finish that can withstand pasteurization conditions includes neck finish threads that engage the closure threads via surface contact. In contrast, FIG. 8A shows a sectional view of a point-type engagement 96 between a lower surface of thread 91 of a container neck finish 90, and an upper surface of a thread 101 of a closure 100. Container thread 91 is vented and has a mostly curved sectional profile, except for two converging surfaces 92 (upper) and 93 (lower), which are substantially planar (as indicated by the dotted lines), the cross-section of which are shown as straight line portions. The lower converging surface 93 of container thread 91 is sloped generally upward when moving away from the container. The two surfaces 92 and 93 converge at a radially outward tip of thread 91 at curved portion 95. The corresponding closure thread 101 (see FIG. 8A) is typically nonvented, has a rounded surface 102 at its radially inward tip, and a substantially planar upper surface 103 (lower surface not shown).
In the prior art, the closure thread profile typically does not match the profile of the neck finish thread at the region of contact. When the closure 100 is applied to neck finish 90, the surface 102 of closure thread 101 contacts neck finish thread 91 at lower surface 93 at the underside of the finish thread 91, resulting in a point contact at point 96 (in the cross-section) between threads 91 and 101. In FIG. 8A, this point contact results from the differing slopes of the substantially planar contacting thread surfaces 93 and 103. As a result, any deformation of either surface 93 or 103 that eliminates the point contact 96 would compromise the seal between threads 91 and 101.
In contrast and in accordance with one embodiment of the invention, a surface area contact is provided between the neck finish and closure threads. Here, the closure and/or neck finish threads to more closely approximate the profiles of the contacting surfaces. In the embodiment of FIG. 8B, a lower surface of finish thread 91 of neck finish 90 contacts an upper surface of thread 111 of closure 110. Thread 111 has a profile similar to that of thread 101 of FIG. 8A, except that the slope of upper planar surface 113 is changed to substantially match the slope of contacting surface 93 of finish thread 91. The matching slopes allow surface contact between closure thread upper surface 113 and neck finish thread lower surface 93, which enhances the seal between closure thread 111 and neck finish thread 91. In one embodiment, a plane of the nonvented threads of the closure skirt contact a plane of the vented threads of the neck finish to achieve the surface contact.
In another embodiment, the surface 93 of neck finish thread 91 in FIG. 8B and the complementary surface 113 of closure thread 110 need not necessarily have flat profiles to achieve surface contact. These complementary surfaces can engage via matching curved planes, so long as more than point contact (e.g., surface contact) is achieved.
In one embodiment, the contacting surfaces of the neck finish thread and of the closure thread are both substantially flat, having an angle with the horizontal of 100 or less. If the matching flat surfaces approach the horizontal, the container thread can penetrate (extend radially into) the closure threads to a greater extent and achieve even greater surface contact. In another embodiment, the matching flat surfaces of the container and closure threads have an angle with the horizontal of 5° or less. In yet another embodiment, the matching flat surfaces of the container and closure threads have an angle with the horizontal of 0°.
Another method of preventing thread deformation involves thickening the finish thread. FIG. 8C shows a modification of a neck finish thread 91 (e.g., the thread 91 of FIG. 8A) by providing an additional thickness 99 on upper surface 92. This additional thickness 99 (in the direction of the longitudinal container axis A) strengthens neck finish thread 91 sufficiently that it is better able to resist deformation. This embodiment allows the use of a conventional closure and neck finish, where only the neck finish is modified with an additional thickness 99. In one embodiment, at least 10% is added to the finish thread thickness; in another embodiment at least 20%, and in a further embodiment at least 30%.
In another embodiment, the ability to withstand deformation by the neck finish threads can be increased by allowing the contact between the neck and closure threads to occur at a distance closer to the neck finish wall. FIG. 8A again is used to show a typical contact point 96 between neck finish thread 91 and closure thread 101. The neck finish thread has a radial depth D (measured from finish wall 97 to curved tip 95) and has a midpoint M. In FIG. 8A, the point contact 96 occurs beyond the midpoint M and near the tip 95.
In contrast, in FIG. 8D the neck finish thread 91 has a lower surface 93 that contacts the upper surface 123 of closure thread 121 (of closure 120) at contact point 96. This is achieved by an increased radial depth of closure thread 121 as compared to the depth of closure thread 101 of FIG. 8A. The contact point 96 of FIG. 8D now is in substantial radial alignment with the midpoint M of neck finish thread 91. As a further example, in FIG. 8E the contact point 96 between engaging surfaces 93 (of neck finish thread 91) and 133 (of closure thread 131) occurs at a point radially closer to the neck finish wall 97, i.e., before midpoint M.
In one embodiment, providing a contact point radially closer to the finish wall enhances the structural stability of the thread because the “bending moment” of the (closure thread) force is reduced. Bending moment is commonly used in solid mechanics to evaluate stresses associated with cantilever beams. The finish thread can be viewed as a cantilever element with the finish wall being the fixed end and the outer edge being the “free” end. The bending moment imposed on the (finish) thread at the wall of the finish (fixed end) is proportional to the distance between the point of contact (point at which the force is acting) and the wall (fixed end). As the point of contact moves closer to the wall (fixed end), this distance is reduced thereby reducing the bending moment and in turn reducing the tendency to bend. Reduction of the bending moment applies whether or not the thread thickens or remains the same when moving from the outer edge of the thread toward the finish wall.
In the embodiment where the thread thickness increases toward the finish wall, moving the point contact 96 toward the neck finish wall 97 can also improve thread integrity because the point contact now occurs at an area of the neck finish thread 91 of greater thickness. For example, in FIG. 8A the depth of the finish thread is 0.057 inch, resulting in a contact point 96 at 0.016 inch from the tip of the thread 95, providing a contact point at 28% the depth of the thread (measured from the tip). In the embodiment of FIG. 8D, point contact 96 occurs at a region where the neck finish thread 91 has greater thickness, compared to the thickness shown in FIG. 8A; in FIG. 8D the contact point 96 occurs at the midpoint distance, i.e., at 0.028 inch, or 50% of the depth of the thread. Still further, FIG. 8E shows an even more ideal situation where the contact point 96 occurs at a distance of 0.037 inch from the tip 95, or 65% the depth of the thread. Accordingly, in one embodiment, the contact point occurs at a distance of at least 50% of the radial depth of the thread as measured from the tip of the thread to the finish wall, e.g., at least 65%, alternatively at least 75%, or even at least 85% of the depth of the thread as measured from the tip of the thread.
Other methods can be used to manipulate the position of point contact 96 to take advantage of the thicker thread region near the finish wall. For example, the angle of the surface of the underside of the finish thread (e.g., the surface 93 of finish thread 91 in FIG. 8A) with the horizontal may be reduced to increase the stability of the thread. The advantage of a flatter thread may arise from the fact that the angle at which the (closure) force acts on the finish thread becomes more vertical. By itself the flatter thread does not change the bending moment. However the vertical nature of the force due to flatness may allow a more radially inward point of engagement between the contacting neck and closure threads. It can also reduce the tendency of the closure thread to “slide” (or strip) out of engagement. Typically, the angle of the underside of the thread finish with the horizontal is 20°. In one embodiment of the invention, this angle is less than 10°, or less than 5°. In another embodiment, this angle is 0°.
In another embodiment, deformation of the thread finish can be prevented by using one or more of the techniques disclosed herein. For example, the engagement between the finish and closure threads can have surface contact that occurs at a region radially closer to the finish wall to take advantage of the greater thread thickness. In one embodiment where the finish and closure threads contact via surface contact, the matching surfaces are flat. In one embodiment, an extremity of the surface contact occurs at a distance of at least 50% the depth of the thread as measured from the tip of the thread to the finish wall. For example, in FIG. 8B which shows surface contact, an extremity of the surface contact occurs at a region between the finish wall and the midpoint of the finish thread depth and thus, occurs at a distance greater than 50% of the depth of the thread as measured from the tip of the thread to the finish wall. The location of the other extremity is generally not as relevant and can occur at a distance less than 50% the depth of the thread. In another embodiment, an extremity of the surface contact occurs at a distance of at least 65%, at least 75%, or at least 85% the depth of the thread as measured from the tip of the thread to the finish wall.
The dimensions of an exemplary finish and closure system able to withstand pasteurization forces can, in one embodiment, be determined by trial runs with closures of varying dimensions and determining whether a test bottle containing fluid can withstand typical pasteurization conditions. In another embodiment, the force experienced by a bottle can be simulated with a test apparatus or system 150, a cross-section of which is schematically depicted in FIG. 9. System 150 includes an oven 152 enclosing a test fixture 154 for applying a force in the direction of the arrow 156. A test finish 158 is supported on surface 160. Inner conical surface 162 of fixture 154 surrounds and contacts the annular top surface 159 of finish 158. Surface 162 is angled from the vertical to model the direction of the force experienced by the finish 158 during pasteurization (see e.g., FIGS. 2B and 2C), while applying an even force to the top surface 159. FIG. 9 depicts the angle 164 from the vertical to be 45°, although angle 164 may be different depending on the dimensions of the neck finish and/or closure.
Advancing of the fixture 154 vertically downward in the direction of arrow 156 is achieved with an air piston. Application of a desired force to the top surface 159 of finish 158 may cause finish 158 to bow inward, e.g., in the manner depicted in FIGS. 2B and 2C. The force is calculated form the product of the area of the piston multiplied by the pressure of the air. Monitoring deformation of the finish (or lack of deformation) under an applied force can guide one of ordinary skill in the art to determine the appropriate dimensions of the closure that can substantially prevent such deformation.
In one embodiment, the outer perimeter of the top surface 159 of the finish 158 experiences a force ranging from 63 lbs (pounds) to 86 lbs applied at an angle 164 of 45° to the vertical plane. The corresponding horizontal component of these forces translates to approximately 44.5 lbs to 60.8 lbs respectively. For a top surface of the finish having an original diameter of 0.982 inch, these forces can reduce the diameter of the top surface of the finish by approximately 0.007 inch to 0.012 inch. As a result, the finish will have a frustocone shape. This range or movement can cause the seal to fail, causing leakage. In one embodiment, a closure having a rigid integral finish support ring of a thickness of approximately 0.040 inch (e.g., finish support ring 53 of FIG. 3) and a diameter of 0.844 inch can resist the range of forces described above. In another embodiment, the rigid external finish support ring extends to a vertical distance of approximately 0.100 inch into the bottle finish (from the top wall of the closure). Although the support ring may yield a small amount when entering the neck of the finish (to achieve a tight fit with the finish neck), the support ring remains sufficiently rigid to prevent the diameter of the top surface of the finish from reducing (moving in) by no more than 0.001 inch. In one embodiment, the support ring is sufficiently rigid to maintain the original diameter of the top surface of the finish even after pasteurization, i.e., there is no reduction in diameter.
As used herein, “a thread” includes at least one thread or thread segment. It is known to utilize a plurality of thread segments, instead of a continuous thread, for one or more of a closure thread and container thread.
As used herein, “a vented thread” means a thread having interruptions, typically vertical cuts or gaps, which allow gas to escape when a user opens the bottle (removes the closure). A “nonvented thread” does not include such vents.
As used herein, “a polyester material” includes one or more polyester homopolymers, copolymers, and blends thereof. The material can include a variety of additives, as typically used in the container industry. These additives may be polymer or nonpolymer additives, and added for various purposes such as processibility, intrinsic viscosity, gas barrier, etc. Similarly, “a polyolefin material,” or any other “material” is not limited to a single polyolefin or a pure polyolefin. Preferably, a polyester material would comprise at least 85% by weight of one or more polyesters, more e.g., at least 90%, or even at least 95%.
A number of modifications and variations will readily suggest themselves to persons of ordinary skill in the art in view of the foregoing description. Directional words such as top, bottom, upper, lower, and the like are employed by way of description and not limitation. The invention is intended to embrace all modifications and variations that fall within the scope of the appended claims.

Claims

1. A plastic closure for supporting an amorphous neck finish of a pasteurizable plastic container against deformation, comprising:

a top wall;

a depending annular skirt extending from the top wall; and

a rigid finish support ring extending from the top wall, the finish support ring having an outer diameter sized to support an inner diameter of the amorphous container neck finish against inward deformation during pasteurization.

2. The plastic closure of claim 1, wherein an inner wall of the skirt includes a thread for engaging a complementary thread on the container neck finish.

3. The plastic closure of claim 1, wherein the plastic closure comprises a polyolefin material and the neck finish comprises one or more of a polyester, polyamide, and polyolefin material.

4. The plastic closure of claim 1, further comprising a liner covering at least a portion of an underside of the top wall.

5. The plastic closure of claim 4, wherein the liner comprises a gas barrier material.

6. The plastic closure of claim 4, wherein the liner covers the area of the top wall defined by the inner diameter of the finish support ring.

7. The plastic closure of claim 4, wherein the liner covers the area of the top wall between the outer diameter of the finish support ring and the inner diameter of the skirt.

8. A plastic closure for supporting an amorphous neck finish of a pasteurizable plastic container against deformation, comprising:

a shell comprising a top wall and a depending annular skirt extending from the top wall;

a liner covering at least a portion of the underside of the top wall; and

a rigid finish support ring extending from the liner, the finish support ring having an outer diameter sized to support an inner diameter of the amorphous container neck finish against inward deformation during pasteurization.

9. The plastic closure of claim 8, wherein the plastic closure comprises a polyolefin material and the neck finish comprises one or more of a polyester, polyamide, and polyolefin material.

10. The plastic closure of claim 8, wherein the liner comprises a polyolefin material and the neck finish comprises one or more of a polyester, polyamide, and polyolefin material.

11. The plastic closure of claim 9, wherein the plastic closure and liner are made from the same material.

12. A pasteurizable package comprising:

a pasteurizable plastic container having an amorphous neck finish; and

a plastic closure comprising a depending annular skirt extending from a top wall and a rigid finish support ring extending from the top wall, the finish support ring having an outer diameter sized to support an inner diameter of the amorphous container neck finish against inward deformation during pasteurization.

13. The package of claim 12, wherein an inner wall of the closure skirt includes a thread for engaging a complementary thread on the container neck finish.

14. The package of claim 12, wherein the container thread is vented and the closure thread is nonvented.

15. The package of claim 12, wherein the engagement between the closure thread and the container thread is by surface contact.

16. The package of claim 15, wherein the surface contact is between a bottom surface of the container thread and a top surface of the closure thread.

17. The package of claim 12, wherein the closure thread is nonvented.

18. The package of claim 12, wherein the closure comprises a polyolefin material and the neck finish comprises one or more of a polyester, polyamide, and polyolefin material

19. The package of claim 18, wherein the closure comprises a polyolefin material and the neck finish comprises a polyethylene terephthalate material.

20. A pasteurizable package comprising:

a plastic pasteurizable container comprising an amorphous neck finish having a vented thread; and

a plastic closure comprising a top wall and a depending annular skirt, an inner wall of the skirt having a nonvented thread that engages the vented thread of the neck finish,

wherein a surface of the nonvented closure thread contacts a surface of the vented container thread to provide surface contact between the closure thread and the container thread and to support the container thread against deformation during pasteurization.

21. The package of claim 20, wherein the surface of the container thread is positioned at the underside of the container thread and contacts an upper surface of the closure thread.

22. The package of claim 20, wherein the surface of the vented container thread and the closure thread are both substantially flat.

23. The package of claim 22, wherein the surface of the vented container thread and the closure thread have an angle with the horizontal of 10° or less.

24. The package of claim 22, wherein the surface of the vented container thread and the closure thread have an angle with the horizontal of 5° or less.

25. The package of claim 22, wherein the surface of the vented container thread and the closure thread have an angle with the horizontal of 0°.

26. The package of claim 20, wherein the surface of the vented container thread and the closure thread are both curved.

27. The package of claim 20, wherein the container comprises a polyethylene terephthalate material.

28. The package of claim 27, wherein the closure comprises a polyolefin material.

29. A pasteurizable package comprising:

a plastic pasteurizable container comprising an amorphous neck finish having a thread; and

a plastic closure comprising a top wall and a depending annular skirt, an inner wall of the skirt having a thread that engages the thread of the neck finish,

wherein the container thread contacts the closure thread at a distance of at least 50% of the radial depth of the thread, as measured from the tip of the thread to a wall of the neck finish, to support the container thread against deformation during pasteurization.

30. The package of claim 29, wherein the container thread contacts the closure thread at a distance of at least 65% of the radial depth of the thread, as measured from the tip of the thread to a wall of the neck finish.

31. The package of claim 29, wherein the container thread contacts the closure thread at a distance of at least 75% of the radial depth of the thread, as measured from the tip of the thread to a wall of the neck finish.

32. The package of claim 29, wherein the container thread contacts the closure thread at a distance of at least 85% of the radial depth of the thread, as measured from the tip of the thread to a wall of the neck finish.

33. The package of claim 29, wherein the container thread contacts the closure thread via a surface at the underside of the container thread.

34. The package of claim 29, wherein the surface at the underside is substantially flat.

35. The package of claim 34, wherein the surface at the underside has an angle with the horizontal of 10° or less.

36. The package of claim 34, wherein the surface at the underside has an angle with the horizontal of 5° or less.

37. The package of claim 34, wherein the surface at the underside has an angle with the horizontal of 0°.

38. The package of claim 29, wherein the contact between the container thread and the closure thread is a point contact.

39. The package of claim 29, wherein the contact between the container thread and the closure thread is a surface contact, wherein one extremity of the surface contact occurs at a distance of at least 50% of the radial depth of the thread, as measured from the tip of the thread to a wall of the neck finish.

40. The package of claim 29, wherein the contact between the container thread and the closure thread is a surface contact, wherein one extremity of the surface contact occurs at a distance of at least 65% of the radial depth of the thread, as measured from the tip of the thread to a wall of the neck finish.

41. The package of claim 29, wherein the contact between the container thread and the closure thread is a surface contact, wherein one extremity of the surface contact occurs at a distance of at least 75% of the radial depth of the thread, as measured from the tip of the thread to a wall of the neck finish.

42. The package of claim 29, wherein the contact between the container thread and the closure thread is a surface contact, wherein one extremity of the surface contact occurs at a distance of at least 85% of the radial depth of the thread, as measured from the tip of the thread to a wall of the neck finish.

43. The package of claim 39, wherein the surface contact occurs between a surface at the underside of the container thread and an upper surface of the closure thread.

44. The package of claim 43, wherein the surface at the underside of the container thread and the upper surface of the closure thread are substantially flat.