Abstract:
A container for containing a heated liquid and having a longitudinal axis. The container comprises at least one substantially vertically folding vacuum panel portion disposed substantially transversely relative to the longitudinal axis, the vacuum panel portion adapted to compensate for vacuum pressure changes within the container caused by heating or cooling of a liquid contained within the container. The vacuum panel portion comprises an initiator portion and a control portion, with at least a portion of the control portion being more steeply inclined relative to the longitudinal axis than at least a portion of the initiator portion. The initiator portion causes the control portion to flex inwardly into the container. The pressure panel inverts vertically in a direction substantially parallel to the longitudinal axis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/432,715, filed on May 12, 2006, which is a continuation of co-pending U.S. patent application Ser. No. 10/363,400, filed on Feb. 26, 2003, which is the U.S National Phase of PCT/NZ01/00176, filed on Aug. 29, 2001, which in turn claims priority to New Zealand Patent Application No. 506684, filed on Aug. 31, 2000, and New Zealand Patent Application No. 512423, filed on Jun. 15, 2001. The entire contents of the aforementioned applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to polyester containers, particularly semi-rigid collapsible containers capable of being filled with hot liquid, and more particularly to an improved construction for initiating collapse in such containers.  
         [0003]     “Hot-Fill” applications impose significant mechanical stress on a container structure. The thin side-wall construction of a conventional container deforms or collapses as the internal container pressure falls following capping because of the subsequent cooling of the liquid contents. Various methods have been devised to sustain such internal pressure change while maintaining a controlled configuration.  
         [0004]     Generally, the polyester must be heat-treated to induce molecular changes resulting in a container that exhibits thermal stability. In addition, the structure of the container must be designed to allow sections, or panels, to “flex” inwardly to vent the internal vacuum and so prevent excess force being applied to the container structure. The amount of “flex” available in prior art, vertically disposed flex panels is limited, however, and as the limit is reached the force is transferred to the side-wall, and in particular the areas between the panels, of the container causing them to fail under any increased load.  
         [0005]     Additionally, vacuum force is required in order to flex the panels inwardly to accomplish pressure stabilization. Therefore, even if the panels are designed to be extremely flexible and efficient, force will still be exerted on the container structure to some degree. The more force that is exerted results in a demand for increased container wall-thickness, which in turn results in increased container cost.  
         [0006]     The principal mode of failure in all prior art known to the applicant is non-recoverable buckling, due to weakness in the structural geometry of the container, when the weight of the container is lowered for commercial advantage. Many attempts to solve this problem have been directed to adding reinforcements to the container side-wall or to the panels themselves, and also to providing panel shapes that flex at lower thresholds of vacuum pressure.  
         [0007]     To date, only containers utilizing vertically oriented vacuum flex panels have been commercially presented and successful.  
         [0008]     In our New Zealand Patent 240448 entitled “Collapsible Container,” a semi-rigid collapsible container is described and claimed in which controlled collapsing is achieved by a plurality of arced panels which are able to resist expansion from internal pressure, but are able to expand transversely to enable collapsing of a folding portion under a longitudinal collapsing force. Much prior art in collapsible containers was disclosed, most of which provided for a bellows-like, or accordion-like vertical collapsing of the container.  
         [0009]     Such accordion-like structures are inherently unsuitable for hot-fill applications, as they exhibit difficulty in maintaining container stability under compressive load. Such containers flex their sidewalls away from the central longitudinal axis of the container. Further, labels cannot be properly applied over such sections due to the vertical movement that takes place. This results in severe label distortion. For successful label application, the surface underneath must be structurally stable, as found in much prior art cold-fill container sidewalls whereby corrugations are provided for increased shape retention of the container under compressive load. Such compressive load could be supplied by either increased top-load or increased vacuum pressure generated within a hot-fill container for example.  
       OBJECTS OF THE INVENTION  
       [0010]     It is an object of the invention to provide a semi-rigid container which is able to more efficiently compensate for vacuum pressure in the container and to overcome or at least ameliate problems with prior art proposals to date and/or to at least provide the public with a useful choice.  
       SUMMARY OF THE INVENTION  
       [0011]     According to one exemplary embodiment, the present invention relates to a container for containing a heated liquid and having a longitudinal axis. The container comprises at least one substantially vertically folding vacuum panel portion disposed substantially transversely relative to the longitudinal axis, the vacuum panel portion adapted to compensate for vacuum pressure changes within the container caused by heating or cooling of a liquid contained within the container. The vacuum panel portion comprises an initiator portion and a control portion, with at least a portion of the control portion being more steeply inclined relative to the longitudinal axis than at least a portion of the initiator portion. The initiator portion causes the control portion to flex inwardly into the container. The pressure panel inverts vertically in a direction substantially parallel to the longitudinal axis.  
         [0012]     According to another exemplary embodiment, the present invention relates to a container for containing a heated liquid and having a longitudinal axis. The container comprises at least one substantially vertically folding vacuum panel portion disposed substantially transversely relative to the longitudinal axis, the vacuum panel portion adapted to compensate for vacuum pressure changes within the container. The vacuum panel portion includes an initiator portion and a control portion, the control portion disposed nearer a side wall and further from the longitudinal axis than the initiator portion. The initiator portion provides for vertical folding before the control portion. The vacuum panel portion inverts vertically under a longitudinally applied force substantially parallel with the longitudinal axis.  
         [0013]     According to yet another exemplary embodiment, the present invention relates to a container for containing a heated liquid and having a longitudinal axis. The container comprises at least one substantially vertically folding vacuum panel portion disposed substantially transversely relative to the longitudinal axis, the vacuum panel portion adapted to compensate for vacuum pressure changes within the container caused by heating or cooling of a liquid contained within the container. The vacuum panel portion comprises an initiator portion and a control portion, with both the initiator portion and the control portion being curved when viewed in a vertical cross-section taken through the longitudinal axis. At least a portion of the control portion is more steeply inclined relative to the longitudinal axis than at least a portion of the initiator portion, and wherein the initiator portion causes the control portion to flex inwardly into the container. The pressure panel inverts vertically in a direction substantially parallel to the longitudinal axis.  
         [0014]     Further aspects of this invention, which should be considered in all its novel aspects, will become apparent from the following description. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]      FIG. 1 : shows diagrammatically an enlarged view of a semi-rigid collapsible container according to one possible embodiment of the invention in its pre-collapsed condition;  
         [0016]      FIG. 2 : shows the container of  FIG. 1  in its collapsed condition;  
         [0017]      FIG. 3 : very diagrammatically shows a cross-sectional view of the container of  FIG. 2  along the arrows A-A;  
         [0018]      FIG. 4 : shows the container of  FIG. 1  along arrows A-A;  
         [0019]      FIG. 5 : shows a container according to a further possible embodiment of the invention;  
         [0020]      FIG. 6 : shows the container of  FIG. 5  after collapse;  
         [0021]      FIG. 7 : shows a cross-sectional view of the container of  FIG. 6  along arrows B-B;  
         [0022]      FIG. 8 : shows a cross-sectional view of the container of  FIG. 5  along arrows B-B;  
         [0023]      FIGS. 9   a  and  9   b : show expanded views of the section between lines X-X and Y-Y of the container of  FIG. 1  in its pre-collapsed and collapsed conditions, respectively;  
         [0024]      FIGS. 10   a  and  10   b : show expanded views of the same section of the container of  FIG. 1  in its pre-collapsed and collapsed conditions, respectively, but with the ribs  3  omitted;  
         [0025]      FIG. 11 : shows an expanded view of the section between lines X-X and Y-Y of the container of  FIG. 5  in its pre-collapsed condition; and  
         [0026]      FIG. 12 : shows an expanded view, similar to  FIG. 11 , of an alternative embodiment of a container according to the present invention, shown in its pre-collapsed condition. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0027]     The present invention relates to collapsible semi-rigid containers having a side-wall with at least one substantially vertically folding vacuum panel section which compensates for vacuum pressure within the container.  
         [0028]     Preferably in one embodiment the flexing may be inwardly, from an applied mechanical force. By calculating the amount of volume reduction that is required to negate the effects of vacuum pressure that would normally occur when the hot liquid cools inside the container, a vertically folding portion can be configured to allow completely for this volume reduction within itself. By mechanically folding the portion down after hot filling, there is complete removal of any vacuum force generated inside the container during liquid cooling. As there is no resulting vacuum pressure remaining inside the cooled container, there is little or no force generated against the sidewall, causing less stress to be applied to the container sidewalls than in prior art. According to an alternative embodiment, the vacuum panel section can be adapted to fold independently of any applied mechanical force (i.e., entirely as a result of vacuum pressure developed within the container). For example, vacuum pressure developed within the container (e.g., as a result of cooling of the contents) can create a force on the vacuum panel substantially aligned with the container&#39;s longitudinal axis, and cause the vacuum panel to fold inwardly into the container.  
         [0029]     Further, by configuring the control portion to have a steep angle, expansion from the collapsed state when the container is uncapped is also prevented. A large amount of force, equivalent to that mechanically applied initially, would be required to revert the control portion to its previous position. This ready evacuation of volume with negation of internal vacuum force is quite unlike prior art vacuum panel container performance.  
         [0030]     The present invention may be a container of any required shape or size and made from any suitable material and by any suitable technique. However, a plastics container blow molded from polyethylene tetraphalate (PET) may be particularly preferred.  
         [0031]     One possible design of semi-rigid container is shown in FIGS.  1  to  4  of the accompanying drawings. The container referenced generally by arrow C is shown with an open neck portion  4  leading to a bulbous upper portion  5 , a central portion  6 , a lower portion  7  and a base  8 .  
         [0032]     The central portion  6  provides a vacuum panel portion that will fold substantially vertically to compensate for vacuum pressure in the container  10  following cooling of the hot liquid.  
         [0033]     The vacuum panel portion has an initiator portion  1  capable of flexing inwardly under low vacuum force and causes a more vertically steeply inclined (a more acute angle relative to the longitudinal axis of the container  10 ), control portion  2  to invert and flex further inwardly into the container  10 . If it were not for flexing of the initiator portion  1 , the container  10  would experience full vacuum force due, for example, from the container cooling. Movement of the initiator portion  1 , and later movement of the vacuum panel, can relieve all or part of the vacuum.  
         [0034]     The provision of an initiator portion  1  allows for a steep, relative to the longitudinal, angle to be utilized in the control portion  2 . Without an initiator portion  1 , the level of force needed to invert the control portion  2  may be undesirably raised. This enables strong resistance to expansion from the collapsed state of the bottle  1 . Further, without an initiator portion to initiate inversion of the control portion, the control portion may be subject to undesirable buckling under compressive vertical load. Such buckling could result in failure of the control portion to fold into itself satisfactorily. Far greater evacuation of volume is therefore generated from a single panel section than from prior art vacuum flex panels. Vacuum pressure is subsequently reduced to a greater degree than prior art proposals causing less stress to be applied to the container side walls.  
         [0035]     Moreover, when the vacuum pressure is adjusted following application of a cap to the neck portion  4  of the container  10  and subsequent cooling of the container contents, it is possible for the collapsing section to cause ambient or even raised pressure conditions inside the container  10 .  
         [0036]     This increased venting of vacuum pressure provides advantageously for less force to be transmitted to the side walls of the container  10 . This allows for less material to be necessarily utilized in the construction of the container  10  making production cheaper. This also allows for less failure under load of the container  10 , and there is much less requirement for panel area to be necessarily deployed in a design of a hot fill container, such as container  10 . Consequently, this allows for the provision of other more aesthetically pleasing designs to be employed in container design for hot fill applications. For example, shapes could be employed that would otherwise suffer detrimentally from the effects of vacuum pressure. Additionally, it would be possible to fully support the label application area, instead of having a “crinkle” area underneath which is present with the voids provided by prior art containers utilizing vertically oriented vacuum flex panels.  
         [0037]     In a particular embodiment of the present invention, support structures  3 , such as raised radial ribs as shown, may be provided around the central portion  6  so that, as seen particularly in  FIGS. 2 and 3 , with the initiator portion  1  and the control portion  2  collapsed, they may ultimately rest in close association and substantial contact with the support structures  3  in order to maintain or contribute to top-load capabilities, as shown at  1   b  and  2   b  and  3   b  in  FIG. 3 .  
         [0038]     In the expanded views of  FIGS. 9   a  and  9   b , the steeper angle of the initiator portion  1  relative to the angle of the control portion  2  is indicated, as is the substantial contact of the support structures  3  with the central portion after it has collapsed.  
         [0039]     In the expanded views of  FIGS. 10   a  and  10   b , the support structures  3  have been omitted, as in the embodiment of  FIG. 5  described later. Also, the central portion  6  illustrates the steeper angle Θ 1  of the initiator portion  1  relative to the angle Θ 2  of the control portion  2  and also the positioning of the vacuum panel following its collapse but without the support structures or ribs  3 .  
         [0040]     In a further embodiment a telescopic vacuum panel is capable of flexing inwardly under low vacuum force, and enables expansion from the collapsed state when the container is uncapped and the vacuum released. Preferably in one embodiment the initiator portion is configured to provide for inward flexing under low vacuum force. The control portion is configured to allow for vacuum compensation appropriate to the container size, such that vacuum force is maintained, but kept relatively low, and only sufficient to draw the vertically folding vacuum panel section down until further vacuum compensation is not required. This will enable expansion from the collapsed state when the container is uncapped and vacuum released. Without the low vacuum force pulling the vertically folding vacuum panel section down, it will reverse in direction immediately due to the forces generated by the memory in the plastic material. This provides for a “tamper-evident” feature for the consumer, allowing as it does for visual confirmation that the product has not been opened previously.  
         [0041]     Additionally, the vertically folding vacuum panel section may employ two opposing initiator portions and two opposing control portions. Reducing the degree of flex required from each control portion subsequently reduces vacuum pressure to a greater degree. This is achieved through employing two control portions, each required to vent only half the amount of vacuum force normally required of a single portion. Vacuum pressure is subsequently reduced more than from prior art vacuum flex panels, which are not easily configured to provide such a volume of ready inward movement. Again, less stress is applied to the container side-walls.  
         [0042]     Moreover, when the vacuum pressure is adjusted following application of the cap to the container, and subsequent cooling of the contents, top load capacity for the container is maintained through sidewall contact occurring through complete vertical collapse of the vacuum panel section.  
         [0043]     Still, further, the telescopic panel provides good annular strengthening to the package when opened.  
         [0044]     Referring now to FIGS.  5  to  8  of the drawings, preferably in this embodiment there are two opposing initiator portions, upper initiator portion  103  and lower initiator portion  105 , and two opposing control portions provided, upper control portion  104  and lower control portion  106 . When the vacuum pressure is adjusted following application of a cap (not shown) to the container  100 , and subsequent cooling of the contents, top load capacity for the container  100  is maintained through upper side-wall  200  and lower side-wall  300  contact occurring through complete or substantially complete vertical collapse of the vacuum panel section, see  FIGS. 6 and 7 .  
         [0045]     This increased venting of vacuum pressure provides advantageously for less force to be transmitted to the side-walls  100  and  300  of the container  100 . This allows for less material to be necessarily utilized in the container construction, making production cheaper.  
         [0046]     This allows for less failure under load of the container  100  and there is no longer any requirement for a vertically oriented panel area to be necessarily deployed in the design of hot-fill containers. Consequently, this allows for the provision of other more aesthetically pleasing designs to be employed in container design for hot-fill applications. Further, this allows for a label to be fully supported by total contact with a side-wall which allows for more rapid and accurate label applications.  
         [0047]     Additionally, when the cap is released from a vacuum filled container that employs two opposing collapsing sections, each control portion  104 ,  106  as seen in  FIG. 7 , is held in a flexed position and will immediately telescope back to its original position, as seen in  FIG. 8 . There is immediately a larger headspace in the container which not only aids in pouring of the contents, but prevents “blow-back” of the contents, or spillage upon first opening.  
         [0048]      FIG. 11  is an enlarged view of a portion of the container  100  depicted in  FIGS. 5-8 . Specifically,  FIG. 11  depicts the portion of container  100  located between the lines X-X and Y-Y of  FIG. 5 . As shown in  FIG. 11 , the initiator portion  103  and/or the control portion  104  can be curved (e.g. when viewed in a vertical cross-section extending through the container&#39;s longitudinal axis A, such as the plane of the paper in  FIG. 11 ). As shown in the exemplary embodiment of  FIG. 11 , the initiator portion  103  and control portion  104  can be substantially continuous with one another. For example, they can form a substantially continuous curve, with at least a portion of the curved control portion  104  being more steeply inclined with respect to the longitudinal axis than at least a portion of the curved initiator portion  103 . Described differently, a portion of the initiator portion  103  can define a tangent line I, and a portion of the control portion can define a tangent line K. Tangent line K can be more steeply inclined with respect to the longitudinal axis A than tangent line I (i.e., tangent line K can define an angle Θ 2  with respect to the longitudinal axis A that is more acute than a corresponding angle Θ 1  defined by tangent line I). Lower initiator portion  103  and lower control portion  106  can have similar curvature(s) to upper initiator portion  103  and upper control portion  104 , or alternatively, can be different. For example, according to an exemplary embodiment, the lower initiator and control portions  105 ,  106  can be substantially linear and discontinuous from one another (e.g., similar to initiator portion  1  and control portion  2  of  FIG. 1 ). According to another exemplary embodiment, the above-described curvature of the initiator portion  103  and/or control portion  104  can apply to a container only having one set of initiator and control portions, such as the container C shown in  FIGS. 1-4  and  9 A- 10 B.  
         [0049]      FIG. 12  is an enlarged, partial view of another exemplary embodiment of a container  200  according to the present invention. According to this exemplary embodiment, the initiator portion  203  is located closer to the longitudinal axis A of the container than is the control portion  204 . Or, in other words, the control portion  204  is located closer to the sidewall  207  than is the initiator portion  203 . Note that while this arrangement is illustrated with respect to curved initiator and control portions  203 ,  204 , it can apply equally to containers having linear initiator and/or control portions (e.g., such as in the container of  FIGS. 1-4 , and  9 A- 10 B). Furthermore, while this embodiment is illustrated with respect to a container having upper initiator and control portions  203 ,  204 , as well as lower initiator and control portions  205 ,  206 , it can apply equally to a container having only one set of initiator and control portions.  
         [0050]     Further embodiments of the present invention may allow for a telescopic vacuum panel to be depressed prior to, or during, the filling process for certain contents that will subsequently develop internal pressure before cooling and requiring vacuum compensation. In this embodiment the panel is compressed vertically, thereby providing for vertical telescopic enlargement during the internal pressure phase to prevent forces being transferred to the side-walls, and then the panel is able to collapse again telescopically to allow for subsequent vacuum compensation.  
         [0051]     Although two panel portions  101  and  102  are shown in the drawings it is envisaged that less than two may be utilized.  
         [0052]     Where in the foregoing description, reference has been made to specific components or integers of the invention having known equivalents then such equivalents are herein incorporated as if individually set forth.  
         [0053]     Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the scope of the invention as defined in the appended claims.