Patent Publication Number: US-11377287-B2

Title: Method of handling a plastic container having a moveable base

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of Ser. No. 16/557,457 filed on Aug. 30, 2019 and published as US 2019/0382181, now U.S. Pat. No. 10,836,552, issued Nov. 17, 2020, which is a divisional of U.S. patent application Ser. No. 15,074,791 (the &#39;791 application), filed on Mar. 18, 2016 and published as US 2017/0197773, now U.S. Pat. No. 10,435,223, issued on Oct. 8, 2019. 
     The &#39;791 application is a continuation of U.S. patent application Ser. No. 13/415,831 (the &#39;831 application), filed on Mar. 8, 2012 and published as US 2013/0312368, now U.S. Pat. No. 9,731,884, issued Aug. 15, 2017. The &#39;831 application is a continuation-in-part of U.S. patent application Ser. No. 11/704,368 (the &#39;368 application), filed on Feb. 9, 2007 and published as US 2008/0047964, now U.S. Pat. No. 8,584,879, issued Nov. 19, 2013. The &#39;831 application is also a continuation-in-part of U.S. patent application Ser. No. 11/704,318 (the &#39;318 application), filed on Feb. 9, 2007 and published as US 2007/0199916. 
     The &#39;831 application is also a continuation-in-part of U.S. patent application Ser. No. 13/412,572 (the &#39;572 application), filed on Mar. 5, 2012, now U.S. Pat. No. 9,145,223, issued Sep. 29, 2015. The &#39;572 application is a continuation of U.S. patent application Ser. No. 11/704,338 (the &#39;338 application), filed on Feb. 9, 2007 and published as US 2007/0199915, now U.S. Pat. No. 8,127,955, issued Mar. 6, 2012. 
     The contents and disclosures of each of the aforementioned applications, their publications and patents are incorporated herein by reference thereto. 
     In addition to the priority applications listed above, the following patents and patent applications also contain related disclosure and are fully incorporated herein by reference: U.S. patent application Ser. No. 10/529,198, filed on Mar. 24, 2005, with a § 371 filing date of Dec. 15, 2005, now U.S. Pat. No. 8,152,010, issued Apr. 10, 2012; International Application No. PCT/NZ2003/000220, filed on Sep. 30, 2003; New Zealand Application Ser. No. 521694, filed on Sep. 30, 2002; U.S. patent application Ser. No. 10/851,083, filed on May 24, 2004, now U.S. Pat. No. 7,543,713, issued Jun. 9, 2009; U.S. application Ser. No. 10/444,616, filed on May 23, 2003 now abandoned; U.S. patent application Ser. No. 10/124,734, filed on Apr. 17, 2002, now U.S. Pat. No. 6,612,451, issued Sep. 2, 2003; U.S. Provisional Patent Application Ser. No. 60/284,795, filed on Apr. 19, 2001; U.S. patent application Ser. No. 10/363,400, entitled “Semi-Rigid Collapsible Container”, filed Feb. 26, 2003, now U.S. Pat. No. 7,077,279, issued Jul. 18, 2006; International Application No. PCT/NZ01/00176, filed Aug. 29, 2001; New Zealand Patent Application Serial No. 506684, filed on Aug. 31, 2000 and entitled, “Semi-Rigid Collapsible Container”; New Zealand Patent Application Serial No. 512423, filed on Jun. 15, 2001 and entitled, “Semi-Rigid Collapsible Container”; International Application No. PCT/US2004/024581, filed on Jul. 30, 2004; U.S. Provisional Patent Application Ser. No. 60/551,771, filed Mar. 11, 2004; U.S. Provisional Patent Application Ser. No. 60/491,179, filed Jul. 30, 2003; U.S. patent application Ser. No. 11/413,124 filed Apr. 28, 2006, now U.S. Pat. No. 8,381,940, issued Feb. 26, 2013; U.S. patent application Ser. No. 10/566,294, filed on Sep. 5, 2006, now U.S. Pat. No. 7,726,106, issued Jun. 1, 2010; U.S. patent application Ser. No. 11/432,715, filed on May 12, 2006, now U.S. Pat. No. 7,717,282, issued May 18, 2010; U.S. patent application Ser. No. 13/284,907, filed Oct. 30, 2011; and U.S. patent application Ser. No. 11/413,583, filed Apr. 28, 2006, now U.S. Pat. No. 8,047,389, issued Nov. 1, 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a hot-fill container structure that allows for the removal of vacuum pressure within the container, and more particularly, to a hot-fill container structure having an invertible vacuum panel deeply set into the base of the container. The present invention also relates to methods of making and processing containers having an invertible vacuum panel deeply set into the base of the container. 
     2. Related Art 
     So called “hot-fill” containers are known in the art. Plastic containers, such as PET containers, are filled with various liquid contents at an elevated temperature, typically around 185 degrees F. Once the liquid within the container cools, the volume of the contained liquid reduces, creating a vacuum within the container that pulls inwardly on the side and end walls of the container. This in turn leads to deformation of the plastic container if it is not constructed rigidly enough to resist the vacuum forces. 
     Typically, vacuum pressures have been accommodated by the use of vacuum panels that deflect inwardly under vacuum pressure. Known vacuum panels are typically located in the container sidewall and extend parallel to the longitudinal axis of the container, and flex inwardly under vacuum pressure toward the longitudinal axis. 
     It is also known in the prior art to have a flexible base region to provide additional vacuum compensation. All such known prior art containers, however, have substantially flat or inwardly recessed base surfaces that deflect further inward to compensate for the vacuum forces. Known flexible base regions have not been able to adequately compensate for the vacuum forces on their own (i.e., vacuum panels in the sidewall and/or or other reinforcing structures are still required). 
     Therefore, there remains a need in the art for plastic containers that overcome the aforementioned shortcomings of the prior art. 
     BRIEF SUMMARY OF THE INVENTIONS 
     The present invention relates to a polymeric or plastic container having an invertible pressure panel located in the container base. The pressure panel is movable from an initial, outwardly-inclined position, to an inverted, inwardly-inclined position, in order to reduce the volume of the container and accommodate for vacuum forces within the container. The entire pressure panel is set deeply into the base of the container, such that no portion of the pressure panel extends beyond the standing ring, regardless of whether the pressure panel is in the initial position or the inverted position. This configuration can allow the container to be supported by the standing ring regardless of whether the pressure panel is in the initial position or the inverted position. 
     Other plastic containers suitable for containing a liquid are disclosed in U.S. Pat. No. 5,261,544 issued to Weaver, Jr.; and U.S. Pat. No. 5,908,128 issued to Krishnakumar et al. As disclosed in Weaver, Col. 5, lines 26-29, a polymeric container should be blow-molded with a minimum thickness of at least about 10 mils. 
     As disclosed in Krishnakumar, Col. 4, lines 17-24, a container of approximately 20 ounces in volume made from ‘bottle grade’ PET (having about 1.5% comonomer and an intrinsic viscosity of about 0.80) may have a side-wall thickness on the order of 0.4 mm, or 15.7 mils, in order to withstand containing a heated liquid. 
     According to one exemplary embodiment, the present invention relates to a plastic container comprising an upper portion including a finish defining an opening into the container, a lower portion including a base defining a standing surface, a sidewall extending between the upper portion and the lower portion, the sidewall defining a longitudinal axis, and at least one substantially transversely-oriented pressure panel located in the lower portion. The pressure panel can be movable between an outwardly-inclined position and an inwardly-inclined position to compensate for a change of pressure inside the container. The standing surface can define a standing plane, and the entire pressure panel can be located between the standing plane and the upper portion of the container when the pressure panel is in the outwardly-inclined position. 
     According to another exemplary embodiment, the present invention relates to a method of processing a plastic container, comprising the steps of (a) providing a plastic container having an upper portion including a finish, a sidewall, a lower portion including a base defining a standing surface, and a substantially transversely-oriented pressure panel located in the base; (b) introducing heated liquid contents into the plastic container with the pressure panel located in an outwardly-inclined position entirely between the standing surface and the upper portion; (c) capping the plastic container; and (d) moving the pressure panel to an inwardly-inclined position entirely between the standing surface and the upper portion. 
     According to yet another exemplary embodiment, the present invention relates to a method of blow molding a plastic container, comprising the steps of (a) enclosing a softened polymer material within a blow mold defining a mold cavity, the blow mold comprising at least first and second side mold portions and a base mold portion; (b) inflating the polymer material within the blow mold to at least partially conform the polymer material to the blow mold cavity; and (c) displacing the base mold portion with respect to the first and second side mold portions to form a transverse pressure panel deeply set within a base portion of the plastic container. 
     Further objectives and advantages, as well as the structure and function of preferred embodiments will become apparent from a consideration of the description, drawings, and examples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. 
         FIG. 1  is a perspective view of an exemplary embodiment of a plastic container according to the present invention, shown with a pressure panel in an initial, outwardly-inclined position; 
         FIG. 2  is a side, sectional view of the plastic container of  FIG. 1 , shown with the pressure panel in the initial, outwardly-inclined position; 
         FIG. 3  is a side, sectional view of the plastic container of  FIG. 1 , shown with the pressure panel in an inverted, inwardly-inclined position; 
         FIG. 4  is a bottom view of the plastic container of  FIG. 1 ; 
         FIG. 5  is a perspective view of another exemplary embodiment of a plastic container according to the present invention, shown with the pressure panel in the initial, outwardly-inclined position; 
         FIG. 6  is a bottom view of the plastic container of  FIG. 5 ; 
         FIG. 7  is a perspective view of a portion of a plastic container according to yet another exemplary embodiment of the present invention, shown with the pressure panel in an initial, outwardly-inclined position; 
         FIG. 8  is a bottom view of the plastic container of  FIG. 7 ; 
         FIG. 9  is a side, sectional view of a portion of the plastic container of  FIG. 7 , shown with the pressure panel in the initial, outwardly-inclined position; 
         FIG. 10  is a side, sectional view of a portion of the plastic container of  FIG. 7 , shown with the pressure panel in the inverted, inwardly-inclined position; 
         FIGS. 11A-11E  schematically illustrate an exemplary method of processing a plastic container according to the present invention; 
         FIGS. 12A-12C  schematically illustrate an exemplary method of forming a plastic container according to the present invention; 
         FIG. 13  is a side view of a portion of a plastic container according to another embodiment of the present invention; 
         FIG. 14  is a side, sectional view of the plastic container of  FIG. 13 , shown with the pressure panel in the initial, outwardly-inclined position; 
         FIG. 15  is a perspective view of the plastic container of  FIG. 13 , shown with the pressure panel in the initial, outwardly-inclined position; 
         FIG. 16  is a side, sectional view of a portion of a plastic container according to another embodiment of the present invention; 
         FIG. 17  is a perspective view of the plastic container of  FIG. 16 , shown with the pressure panel in the initial, outwardly-inclined position; 
         FIG. 18  is a side, sectional view of a portion of a plastic container according to another embodiment of the present invention; 
         FIG. 19  is a perspective view of the plastic container of  FIG. 18 , shown with the pressure panel in the initial, outwardly-inclined position; 
         FIG. 20  is a schematic representation of a system for handling plastic containers; 
         FIG. 21  is a schematic representation of handling plastic containers; 
         FIG. 22  illustrates a lower portion of a container similar to that shown in  FIG. 7  according to an alternate embodiment; 
         FIG. 23  illustrates a lower portion of the container of  FIG. 13  similar to the view shown in  FIG. 8  according to an alternate embodiment; 
         FIG. 24  is a bottom plan view of  FIG. 8  with planes C-C and D-D indicated; 
         FIG. 25  is a side section view of  FIG. 15  taken along C-C; 
         FIG. 26  is a side section view of  FIG. 15  taken along D-D; 
         FIG. 27A  is a side view of the plastic container of  FIG. 5 ; 
         FIGS. 27B and 27E  are side sectional views of the plastic container of  FIG. 6  through plane B-B; and, 
         FIGS. 27C and 27D  are side sectional views of the plastic container of  FIG. 6  through plane C-C. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention are discussed in detail below. In describing embodiments, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without departing from the spirit and scope of the invention. All references cited herein are incorporated by reference as if each had been individually incorporated. 
     As discussed above, to accommodate vacuum forces during cooling of the liquid contents within a hot-fill container, plastic containers have typically included a series of vacuum panels located around the sidewall and/or in the base portion. The vacuum panels deform inwardly, and the base deforms upwardly, under the influence of the vacuum forces. This configuration attempts to prevent unwanted distortion elsewhere in the container. However, the container is still subjected to internal vacuum forces. The sidewalls and base merely provide a suitably resistant structure against that force. Additionally, the vacuum panels in the sidewall can undesirably detract from the appearance and feel of the container, and limit the design possibilities for the container. 
     Typically at a bottling plant, the containers are filled with a hot liquid and then capped before being subjected to a cold water spray, resulting in the formation of a vacuum within the container. The container structure needs to be able to cope with this vacuum force. U.S. patent application Ser. No. 10/529,198, filed on Dec. 15, 2005, the entire content of which is incorporated herein by reference, discloses hot-fill containers that provide for the substantial removal or substantial negation of the vacuum pressure within the containers. The disclosed containers include a transversely-oriented pressure panel located in the container base. The pressure panel is movable between an initial, outwardly inclined position, and an inverted, inwardly inclined position, in order to reduce the volume of the container and accommodate for vacuum forces within the container. The present invention relates to additional embodiments of this concept in which the pressure panel is set deeply into the base of the container, such that no portion of the pressure panel extends beyond the standing ring, regardless of whether the pressure panel is in the initial position or in the inverted position. 
     This configuration can allow the container to be supported by the standing ring regardless of whether the pressure panel is in the initial position or the inverted position. 
     Referring to  FIGS. 1-4 , an exemplary embodiment of a plastic container  10  according to the present invention is shown. The container  10  can include an upper portion  12  including a finish  14  that defines an opening into the interior of the container  10 . As shown, the finish  14  can include threads  16  or other structures adapted to secure a closure (not shown) onto the container  10 . The container  10  can also include a lower portion  18  having a base  20 , and a sidewall  22  extending between the upper portion  12  and the lower portion  18 . The base  20  can define a standing surface  21  that is substantially flat and adapted to support the container  10  in a substantially upright position (e.g., with longitudinal axis A substantially perpendicular to the surface on which container  10  is resting). 
     In the exemplary embodiment shown, the sidewall  22  is substantially tubular and has a substantially circular transverse cross-sectional shape. Alternative cross-sectional shapes can include, for example, an oval transverse cross-section; a substantially square transverse cross-section; other substantially polygonal transverse cross-sectional shapes such as triangular, pentagonal, etc.; or combinations of curved and arced shapes with linear shapes. As will be understood by one of ordinary skill in the art, when the container  10  has a substantially polygonal transverse cross-sectional shape, the corners of the polygon are typically rounded or chamfered. Although the container  10  is shown as having reinforcing ribs or rings  23  in the sidewall  22  to resist paneling, dents and other unwanted deformation of the sidewall, particularly under vacuum force, other embodiments are possible where the sidewall  22  is substantially devoid of such features (e.g., the sidewall  22  can be smooth like that of a conventional glass container). 
     As best seen in  FIG. 4 , a portion of the base  20  can include a plurality of reinforcing ribs  24 , however other embodiments with or without the reinforcing ribs  24  are possible. 
     The lower portion  18  of the container  10 , and particularly the base  20 , can include a substantially transversely-oriented pressure panel  26 . The pressure panel  26  can be moved between an outwardly-inclined position (shown in  FIGS. 1 and 2 ) and an inwardly-inclined position (shown in  FIG. 3 ) in order to reduce the internal volume of the container  10  and compensate for any vacuum forces created within the container, for example, during the filling process. For example, the pressure panel  26  may substantially remove the internal vacuum that develops within the container  10  during a hot-fill process once the container  10  has been hot-filled, capped, and cooled. 
     As best seen in the sectional views of  FIGS. 2 and 3 , the pressure panel  26  can be deeply set into the container  10  in order to facilitate standing of the container  10  on its standing surface  21  regardless of whether the pressure panel  26  is located in the outwardly-inclined position ( FIG. 2 ) or the inwardly-inclined position ( FIG. 3 ). In other words, the entire pressure panel  26  structure can be located between the plane P of the standing surface  21  and the upper portion  12  of the container  10  when the pressure panel  26  is in the outwardly-inclined position ( FIG. 2 ) and also when the pressure panel  26  is in the inwardly-inclined position ( FIG. 3 ). 
     According to the exemplary embodiment shown in  FIGS. 1-4 , the lower portion  18  of the container  10  includes a concave outer wall portion  30  that extends from the lower end of the sidewall  22  to the standing surface  21 . The standing surface may be a ring or annular portion as shown in  FIG. 1 , or may be discontinuous as shown in  FIG. 5 . The pressure panel  26  is deeply set into the lower portion  18  of the container  10  via an inner wall  32  that extends from the standing surface  21  to the pressure panel  26 . The inner wall may therefore comprise an instep or hollow recessed portion between the pressure panel  26  and the standing surface  21 . In the exemplary embodiment shown, the inner wall  32  is parallel or nearly parallel to the longitudinal axis A of the container  10 , and provides the recessed portion with a concave annular ring shape; however, other configurations and/or inclinations of the inner wall  32  are possible that are not concave annular ring structures, and may have different angles as shown in  FIGS. 18-19  with reference to the inner wall  1120 . In addition, one of ordinary skill in the art will know that other configurations besides the inner wall  32  may be implemented to set the pressure panel  26  deeply into the lower portion  18 . An annular, recessed channel  34  can be provided in the inner wall  32  adjacent the standing surface  21  to provide a further recessed concave ring structure in the inner wall  32 . In the exemplary embodiment shown, the annular recessed channel has a substantially square or annular cross-section, however, other shapes are possible for the channel to be inwardly stepped. Channel  34  can act as a rib member and reinforce the foot portion or standing surface  21  and/or facilitate stacking of multiple containers on top of one another, depending on the shape and size of the finish  14  and/or closure. 
     In the exemplary embodiment of  FIGS. 1-4 , the standing surface  21 , inner wall  32 , and outer wall  30  are substantially continuous about the circumference of the container  10  (see  FIG. 4 ). However, as shown in the alternative embodiment of  FIGS. 5 and 6 , and  FIGS. 27A-27E , the container  10 ′ can have a standing surface  21 , inner wall  32 ′, and outer wall  30 ′ that are discontinuous. 
     The pressure panel or inner annular wall  240  has an inner periphery  244  and an outer periphery  242 , and is set, with respect to the longitudinal axis and the opening into the container, at an outward or downward angle prior to filling with a heated liquid. The outer annular wall includes support or foot portions  230  and the inner wall portions  32 ′ extend from the standing surfaces  21 ′ to the inner annular wall or pressure panel  240 . Radial webs or straps  246  are uniformly spaced apart and separate each support  230 . The web surface is closer to the finish than the footed contact surface, or expressed another way, the webs  246  are longitudinally displaced above the footed contact surface  21 ′. In addition, each support  230  has a larger arcuate extent than that of each radial web  246 . The inner annular wall  240  extends within the concave outer annular wall  30 ′. The outer periphery  242  of the inner annular wall or pressure panel  240  merges with the inner wall  32 ′ of each of the supports  230 , and with the plurality of spaced-apart, horizontally disposed, radial webs or straps  246  located adjacent the outer periphery  232  of the standing surface of the base. Each of the webs  246  extends between the supports  230  and connects to the container sidewall  22  in the lower portion  18  at an elevation above the horizontal plane “P” extending through the standing surface  21  to form radius  202  such that web surface  246  is visible from a side of the container. Preferably the inner annular wall  240  and the central dimple or push up  248  merge via an annular hinge  250  at the foot of the push-up, comprising radius  251 . 
     In order to facilitate movement (e.g., folding) of the pressure panel  26  between the outwardly-inclined position of  FIG. 2  and the inwardly-inclined position of  FIG. 3 , pressure panel  26  can include a decoupling or hinge structure  36  that is located between the inner wall  32  and the pressure panel  26 . In the exemplary embodiment shown, the hinge structure  36  comprises a substantially flat, non-ribbed region, that is susceptible to folding, however, other configurations of the hinge structure, such as a crease, are possible. 
     Referring now particularly to  FIG. 4 , the pressure panel  26  can comprise an initiator portion  40  and a control portion  42 . Both the initiator portion  40  and control portion  42  can comprise part of the pressure panel  26  that folds when the pressure panel  26  is moved from its initial position in  FIG. 2  to its inverted position in  FIG. 3 . The initiator portion  40  can be adapted to move or fold before the rest of the pressure panel  26  (e.g., before the control portion  42 ). In the exemplary embodiment shown, the control portion  42  is at a steeper angle to the standing plane P than the initiator portion  40 , thereby resisting expansion of the pressure panel from the inverted state ( FIG. 3 ) to the initial state ( FIG. 2 ), for example, if the container  10  were accidentally dropped. 
     In order to maximize the amount of vacuum compensation from the pressure panel  26 , it is preferable for at least the control portion  42  to have a steep angle of inclination with respect to the standing plane P. As shown in  FIG. 2 , the control portion  42  can be at a first angle alpha, with respect to the standing plane P. According to one exemplary embodiment, the first angle alpha, can be at least 10 degrees, and preferably is between about 30 degrees and about 45 degrees. According to this embodiment, the initiator portion  1  can be at a second angle beta, with respect to standing plane P, that is at least 10 degrees less than the first angle alpha. 
     When the pressure panel is inverted from the outward state ( FIG. 2 ) to the inward state ( FIG. 3 ), it can undergo an angular change that is approximately equal to its angle of inclination. For example, if the control portion  42  is initially set at an angle alpha, of about 10 degrees, it will provide an angular change of approximately 20 degrees. At such a low angle of inclination, however, it can be difficult to provide an adequate amount of vacuum compensation in a hot-filled container. Therefore it is preferable to provide the initiator portion  40  and control portion  42  with steeper angles. For example, with the control portion set at an angle alpha, of about 35 degrees, the pressure panel  26  will undergo an angular change of about 70 degrees upon inversion. According to this exemplary embodiment, the initiator portion  40  can be set at an angle beta, of about 20 degrees. 
     Referring to  FIGS. 22-23 , a base portion of a container according to an alternative embodiment is shown, wherein the control portion of the pressure panel comprises a substantially continuous conical area extending around the base. According to this embodiment, the initiator portion  140  and the control portion  142  are set at a common angle, such that they form a substantially uniform pressure panel  126 . However, initiator portion  140  may still be configured to provide the least amount of resistance to inversion of pressure panel  126 , such that it still provides an initial area of folding or inversion. For example, the initiator portion  140  may have a smaller material thickness than the control portion  142 . According to the embodiment shown in  FIGS. 22-23 , initiator portion  140  causes the pressure panel  126  to begin inversion at its region of widest diameter, near the hinge structure  136 . 
     Additional structures may be added to the pressure panel  126  in order to add further control over the inversion process. For example, the pressure panel  126  may be divided into fluted regions, as shown in  FIGS. 6 and 7 . As shown, the fluted regions  145  can be outwardly convex, resulting in inward creases  127  between each outward flute and evenly distributed around the container&#39;s longitudinal axis to create alternating regions of greater and lesser angular inclination. Referring to  FIGS. 24-26  in particular, panel portions  145  that are convex outwardly, and evenly distributed around the central axis create regions of greater angular set  219  and regions of lesser angular set  218 . The angular set in the midline  218  of each of the plurality of flutes  145  has lesser angular set gamma than the angular set delta in the plurality of creases  218  created between each fluted panel portion  145 . This may provide for greater control over the inversion of the panel. Such geometry provides increased resistance to reversion of the panel, and a more even distribution of forces when in the inverted position. This type of geometry can provide increased resistance against the panel returning from the inward position ( FIG. 10 ) to the outward position ( FIG. 9 ), for example, if the container were dropped. The fluted configuration can also provide more even distribution offerees on the pressure panel  126 . According to an alternative embodiment, the flutes can be inwardly concave. Inwardly directed flutes offer less resistance to initial inverting forces, coupled with increased resistance to reverting back to the original, outward position. In his way, they behave in much the same manner as ribs to prevent the panel being forced back out of the outwardly inclined position, but allow for hinge movement from the first outwardly inclined position to the inwardly inclined position. Such inwardly or outwardly directed flutes or projections function as ribs to increase the force required to invert the panel. Further details regarding the pressure panel and fluting are disclosed in co-pending U.S. patent application Ser. No. 10/529,198, filed on Dec. 15, 2005, the entire content of which is incorporated herein by reference. 
       FIGS. 13 to 15  show another exemplary embodiment of a container that can be used as described herein. The container includes an upper portion  1102 , shoulder  1104 , body  1106  and base  1108 . The upper portion  1102  includes an opening into the container which may be closed and sealed, such as via a screw cap using thread  1112 . 
     The container body  1106  in the present example includes ribs  1114  in a first region thereof and panels  1116  in second portions thereof. Panels  1116  in this example act as vacuum panels as discussed below and also facilitate gripping of the container by a consumer, but in other examples may be configured to serve only as grip panels and not pressure panels. In another example, vacuum panels may be placed in the container body separately from the grips or without the grips. 
     The container base  1108  includes standing ring or bearing surface  1118  on which the container rests when in an upright position. Adjacent the standing ring  1118  is a recess or instep forming a first wall  1120  which joins pressure panel or second wall  1124  via a hinge structure  1122 . An inwardly projecting push-up or section  1126  is provided in the center of the base  1108 . The panel or second wall  1124  may include creases  1128  as shown which aid control over the configuration of the panel or second wall  1124  as it moves between outwardly and inwardly inclined positions. 
     The container of  FIGS. 13 to 15  is particularly adapted to hot-fill applications but may be used in other applications where there are changes in pressure inside the container. 
     According to one hot-filling method using the container of  FIGS. 13-15 , the container is provided to a filling station with the second wall  1124  configured as shown in  FIGS. 14 and 15 . The container is then filled with hot or heated liquid and sealed, for example, using a screw cap. As the container cools, contents of the container (particularly the headspace), contract. This causes the pressure in the container to drop. Cooling may be accelerated, for example, by spraying the outside of the container with water. 
     To prevent unwanted deformation of the container caused by the reduction in internal pressure, one or both pressure panels  1116 ,  1124  are configured to move inwards to reduce the container volume and increase the internal pressure of the container. In one example, at least the panels  1116  provided in the container sidewall are adapted to move inwards through action of the vacuum force generated inside the container during cooling, and in another example the panel  1124  is adapted to move inward through action of the vacuum force generated inside the container during cooling. In a third example, both move inward, and in a further example, the container sidewalls are subjected to vacuum force prior to the base. 
     In the present example, panel  1124  is also configured to move to adjust the container volume. More particularly, panel  1124  is configured to invert about hinge structure  1122  from being outwardly inclined as shown in  FIGS. 14 and 15  to being inwardly inclined (not shown). 
     Inversion of the panel  1124  may be initiated by engagement of a pusher or other external mechanical force against the base  1108 , preferably the centrally located push-up  1126  of the base  1108 . Additionally or alternatively, the panel  1124  may include an initiator portion that is configured to initiate or cause the rest of the panel to move between the outwardly and inwardly inclined positions. The initiator portion may reduce or obviate the need for a pusher, providing for movement of the panel  1124  due to the forces generated by the pressure differential between the inside and outside of the container. To this end, the initiator portion may have a lower angle of inclination than other portions of the panel  1124  relative to the standing plane formed by the standing ring  1118 . 
     According to preferred embodiments, opposing vacuum panels  1116  are subjected to vacuum force prior to repositioning of the base. More preferably, the vacuum panels  1116  move inwards prior to movement of the second wall  30  or panel  1124  to the inwardly inclined position. Other methods of using containers as described herein can also be used with the container of  FIGS. 13-15 . 
     It will be noted that the instep or first wall  1120  is configured so as to elevate the panel  1124  and other portions of the base  1108  above the standing ring  1118  when the panel  1124  is outwardly inclined. Such a configuration provides improved container stability during the filling operations. However, the instep or first wall  1120  may be recessed to a lesser extent such that a portion of the base extends below the standing ring  1118  when the panel  1124  is outwardly inclined. As will be appreciated, this will mean that different portions of the container base  1108  act as the standing ring depending on whether the panel or second wall  1124  is inwardly or outwardly inclined. 
     The container shown in  FIGS. 13 to 15  may also be used in pasteurisation processes. According to an example such process, the container is filled with the panel  1116 ,  1124  in the inward position and then sealed. The container and its contents are then heated, causing an increase in internal pressure. As a result of this the panels  1116 ,  1124  move to an outward position. After the heating stage of the pasteurisation process is completed and the container is cooled, the panels  1116 ,  1124  preferably revert to the inwardly inclined position. 
     According to preferred embodiments, different stages of the filling and/or pasteurisation processes may be performed at different stations within a filling or processing facility. To this end, the container may be conveyed in between stages or during a particular stage depending on system requirements and preferences. 
       FIGS. 16 and 17  show a container according to another embodiment. Many of the features of this embodiment are the same or substantially the same as those of the embodiment of  FIGS. 13 to 15  and like references have been used to aid clarity. Only features that differ from the embodiment of  FIGS. 13 to 15  will be described. 
     As shown in  FIGS. 16 and 17 , the container of this embodiment includes first and second panels  1116  on two opposing faces of the sidewall thereof, at least one of which is a vacuum panel. 
       FIGS. 18 and 19  show another embodiment of a container that is substantially identical to the container of  FIGS. 16 and 17  and again only points of difference will be described. 
     Notably, in the embodiment of  FIGS. 18 and 19 , the first wall or instep  1120  is inclined at a lesser angle than in the embodiment of  FIGS. 16 and 17 . As will be appreciated, other angles of inclination may also be used. 
     The operation or preferred use of the containers of  FIGS. 16 and 17 , and  FIGS. 18 and 19 , is substantially identical to that described in relation to the embodiment of  FIGS. 13 to 15 . 
     Referring to  FIGS. 11A-11E , an exemplary method of processing a plastic container according to the present invention is shown. Prior to processing, the container  10  may be formed (e.g., blow molded) with the pressure panel  26  in the inwardly-inclined position. According to this embodiment, a force can be applied to the pressure panel  26  in order to move the pressure panel  26  into the outwardly-inclined position. For example, as shown in  FIGS. 11A and 11B , a first mechanical pusher  50  can be introduced through the opening in the container finish  14  and forced downwardly on the pressure panel  26  in order to move it to the outwardly-inclined position (shown in  FIG. 11C ). One of ordinary skill in the art will know that other types of mechanical or other forces can alternatively be used to move the pressure panel  26  into the outwardly-inclined position. Alternatively, the container  10  can be initially formed with the pressure panel  26  located in the outwardly-inclined position. 
     Referring to  FIG. 11C , the container  10  can be filled with liquid contents when the pressure panel  26  is located in the outwardly-inclined position. Particularly, the container  10  can be “hot-filled” with the liquid contents at an elevated temperature, for example, 185 degrees C. As shown in  FIG. 11C , the liquid contents can be introduced into the container  10  via a filling nozzle  52  inserted through the opening in the container finish  10 , although one of ordinary skill in the art will know that any number of known filling devices and techniques can be implemented. According to an alternative embodiment, the first mechanical pusher  50  and the filling nozzle  52  can be the same instrument. 
     Referring to  FIG. 11D , once the container  10  has been filled to the desired level, the filling nozzle  52  can be removed, and a cap  54  can be applied to the container finish  14 . Any number of capping techniques and devices known in the art can be used to apply the cap  54  to the container finish  14 . Next the container  10  can be cooled, for example, by spraying the container  10  with cool water, or alternatively, by leaving the container  10  in ambient conditions for a sufficient amount of time. As the container  10  and its contents cool, the contents tend to contract. This volumetric change inside the sealed container  10  can create a vacuum force within the container  10 . 
     In order to alleviate all or a portion of the vacuum forces within the container  10 , the pressure panel  26  can be moved from the outwardly-inclined position of  FIG. 11D  to the inwardly-inclined position of  FIG. 11E . For example, following filling, capping, and cooling of the container  10 , an external force can be applied to the pressure panel  26 , for example, by a second mechanical pusher  56 , as shown in  FIG. 11D . Alternatively, the pressure panel  26  can be moved by the creation of relative movement of the container  10  relative to a punch or similar apparatus, in order to force the pressure panel  26  into the inwardly-inclined position. Alternatively, the pressure panel  26  can invert to the inwardly-inclined position under the internal vacuum forces within the sealed container  10 . For example, all or a portion of the pressure panel  26  (e.g., the initiator portion) can be made flexible enough to cause the pressure panel  26  to invert under the internal vacuum forces. 
     The inversion of the pressure panel  26  from the outwardly-inclined position to the inwardly-inclined position reduces the internal volume of the container  10 , and thereby increases the pressure inside the sealed container  10 . This can alleviate any vacuum created within the container  10  due to the hot-fill process. This can also remedy any deformation of the container  10  that was caused as a result of the internal vacuum. 
     As shown in  FIGS. 11A-E , the entire pressure panel  26  is above the plane P of the standing surface  21  (see  FIG. 11C ) of the container  10 . As a result of this configuration, the containers  10  according to the present invention can be stored, transported, and capped/filled, etc., all while standing on the standing surface  21 . This can eliminate the need for any adapters or other devices to stabilize the container  10  in the upright position. This can also make the containers  10  of the present invention more readily adapted for use with conventional, existing container transports, capping and filling stations, and storage facilities. 
     Referring to  FIGS. 12A-C , an exemplary method of blow molding a plastic container according to the present invention is shown. Referring to  FIG. 12A , the method includes enclosing a softened polymer material (such as PET, PEN, PP, blends thereof, and other suitable materials known in the art) within a blow mold. In the exemplary embodiment shown, the polymer material comprises a plastic container preform  60 . However, according to an alternative embodiment, the polymer material can comprise a tube of extruded polymer material, for example, as used in the known process of “extrusion blow molding.” 
     The blow mold can comprise two or more side mold portions  62 ,  64 , and a base mold portion  66 . The side mold portions  62 ,  64  can move from an open position (not shown) in which the side mold portions are separated from one another, to a closed position, shown in  FIGS. 12A-C . In the closed position, shown, the side mold portions  62 ,  64  define a mold cavity  68  having an open bottom. The mold cavity  68  corresponds to the shape of a plastic container to be molded therein. The base mold portion  66  is located in the open bottom region of the mold cavity  68  and is movable with respect to the side mold portions  62 ,  64  in the vertical direction (as viewed in  FIGS. 12A-C ) between the retracted position shown in  FIGS. 12A and 12B , and the extended position shown in  FIG. 12C . Mechanical, pneumatic, hydraulic, or other means known in the art can be implemented to move the base mold portion  66  between the retracted and extended positions. 
     A stretch rod  70  can be inserted into the neck portion of the softened preform  60 , and can be used to stretch or elongate the preform  60 . Air or another medium can be expelled from the stretch rod  70  or other device to at least partially inflate the preform  60  into conformity with the mold cavity  68  in what is commonly known in the art of stretch blow molding as a “pre-blow” step. Preferably, the preform  60  is inflated into substantially complete conformity with the mold cavity  68  while the base mold portion  66  is in the retracted position, as shown in  FIG. 12B . In order to stretch blow mold the container from the partially inflated volume, it is commonly known in the art of stretch blow molding to increase the pressure during the final blowing step in order to force the plastic material into complete conformity with the mold cavity  68 . This can eliminate the need for the polymer material to expand deeply into tight corners, narrow spaces, etc., that are associated with the deeply-set pressure panel of the present invention. This can avoid resultant thin or weak spots in the formed container. While the polymer material is still in a softened state, the base mold portion  66  can be displaced upwardly into the mold cavity  68  to form a transverse pressure panel deeply set within the base portion of the plastic container (see, for example, the base  20  and pressure panel  26  of  FIGS. 1-4 ). Air can continue to be expelled to blowing pressure into the stretch rod in the blow mold cavity during displacement of the base mold portion  66  to the extended position, or alternatively, the supply of air can be turned off. Referring to  FIGS. 1-4 , by “deeply set” it is meant that the pressure panel  26  is located entirely between the standing plane P and the upper portion  12  of the container when the pressure panel  26  is in the outwardly-inclined position ( FIG. 2 ) and when it is in the inwardly-inclined position ( FIG. 3 ). In the exemplary embodiment of  FIGS. 12A-C , the base mold portion  66  moves substantially along the longitudinal axis of the plastic container being formed in the mold cavity  68 , however, other orientations are possible. 
     Once the plastic container has been formed in the mold cavity  68 , the base mold portion  66  can return to the retracted position, and the side mold portions  62 ,  64  can separate to release the formed container. 
     By utilizing the blow molding method of the present invention, it is possible to initially form the general container shape with a generally flat bottom portion, and then deflect the bottom upwardly at orientation temperature. As a result, the container base and deeply-set pressure panel can be of improved material thickness and uniformity. In addition, the base and pressure panel can be multi-axially stretch oriented to provide increased strength without the attendant thinness or weakness at the heel portion of the bottle. 
     The base of the plastic container according to the present invention is preferably crystallized to some extent. Some degree of crystallinity and/or biaxial orientation can be achieved normally during the blow molding process. However, crystallization can be promoted through heat setting of the container. For example, the walls and base of the mold can be held at an elevated temperature to promote crystallization. When the container is heat set at a temperature of about 180 degrees F., the container sidewalls, base, pressure panel, etc., can be typically crystallized to about 20%. This degree of crystallinity is typical for a blow molding process and does not represent a significant amount of heat setting or increased crystallinity or orientation, as compared with a typically prepared container. However, the properties of the base and pressure panel of the present invention can be advantageously enhanced by heat setting the container, and particularly the base and pressure panel, at ever higher temperatures. Such temperatures can be, for example, greater than 250 degrees F. and can be 325 degrees F. or even higher. When these elevated heat set temperatures are utilized, crystallinity can be increased to greater than 20% or 25% or more. One drawback of increasing crystallinity and biaxial orientation in a plastic container is that this process introduces opacity into the normally clear material. However, unlike bases in prior art containers, which can require a crystallinity of 30% or more, utilizing crystallinities of as low as 22-25% with a base structure according to the present invention can achieve significant structural integrity, while maintaining the substantial clarity of a base that is preferred by manufacturers, packagers and consumers. 
     U.S. Pat. Nos. 4,465,199; 3,949,033; 4,378,328; and 5,004,109, all of which are incorporated herein by reference, disclose further details relating to blow molding methods utilizing displaceable mold portions. The methods disclosed in these references can also be implemented to form plastic containers according to the present invention. According to an alternative embodiment of the invention, the plastic container can be removed from the blow mold prior to forming the deeply-set pressure panel. Outside of the mold, the pressure-panel and related structure(s) can be formed in the base of the plastic container using a mandrel or similar device. U.S. Pat. No. 4,117,062, the entire content of which is incorporated herein by reference, provides further details on this type of post-mold processing. 
     The embodiments illustrated and discussed in this specification are intended only to teach those skilled in the art the best way known to the inventors to make and use the invention. Nothing in this specification should be considered as limiting the scope of the present invention. All examples presented are representative and non-limiting. The above-described embodiments of the invention may be modified or varied, without departing from the invention, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the claims and their equivalents, the invention may be practiced otherwise than as specifically described.