Abstract:
A closure for a container, and a container incorporating the same, that minimizes or eliminates leakage between the closure and the container holding the liquid. The closure provides a liquid sealing system that allows irregularly shaped closure tops to be used without sacrificing the effectiveness of the liquid seal. In one embodiment, the closure includes a plurality of struts disposed within an annular space that receives a neck portion of the container to create a seating plane that corresponds to a plane formed by the rim of the neck portion.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application No. 61/230,253, filed Jul. 31, 2009, the entirety of which is hereby incorporated by reference. 
    
    
     FIELD 
     The present invention relates generally to containers, and specifically to a closure suitable for liquid-filled containers. 
     BACKGROUND 
     A challenge in modern product packaging has been to provide container caps or closures that are aesthetically interesting to the consumer, provide brand differentiation, are light-weight in construction, economical to produce, and effectively seal the liquid contents of the container. In order to prevent leakage, conventional closures have been generally designed with flat, uniform top surface configurations so that the underside of the closure has a correspondingly flat annular surface for mating with the flat annular neck rim at the mouth of the container. This situation has heretofore limited the freedom of packaging designers in developing interesting cap configurations while still providing a satisfactory liquid seal. 
     An improved closure is desired that allows different and irregular configurations to be utilized without sacrificing the integrity of the liquid seal. 
     SUMMARY 
     A closure is provided that minimizes or eliminates leakage between the closure and a container holding a liquid. The closure provides a liquid sealing system that allows irregularly shaped closure tops to be used without sacrificing the effectiveness of the liquid seal. 
     In one aspect, the invention can be a container comprising: a container neck forming an opening about an axis, the container neck comprising a rim surface that defines a seating plane; a closure body comprising: a top wall extending radially from the axis; a plug extending axially from the top wall, the plug circumferentially surrounding the axis; a sidewall extending axially from the top wall and circumferentially surrounding the plug so as to form an annular space between the sidewall and the plug; a bottom surface of the top wall defining a roof of the annular space, the bottom surface of the top wall being non-coplanar with a reference plane that is substantially parallel to the seating plane; and a plurality of circumferentially spaced-apart struts in the annular gap, each of the struts having a bottom surface that collectively define the reference plane; and the closure body secured to the container neck, the container neck extending into the annular gap so that the rim surface of the container neck contacts the bottoms surfaces of the struts, the plug extending into the opening of the container neck and forming a seal with the container neck. 
     In another embodiment, the invention can be a closure for sealing a liquid container comprising: an axis; a top wall extending radially from the axis; a plug extending axially from the top wall, the plug circumferentially surrounding the axis; a sidewall extending axially from the top wall and circumferentially surrounding the plug so as to form an annular space between the sidewall and the plug; a bottom surface of the top wall defining a roof of the annular space, the bottom surface of the top wall being non-coplanar with a reference plane that is substantially perpendicular to the axis; and a plurality of circumferentially spaced-apart struts in the annular gap, each of the struts having a bottom surface that collectively define a seating plane that is substantially perpendicular to the axis. 
     In yet another aspect, the invention can be a closure for sealing a liquid container comprising: a axis; a top wall extending radially from the axis; a plug extending axially from the top wall, the plug circumferentially surrounding the axis; a sidewall extending axially from the top wall and circumferentially surrounding the plug so as to form an annular space between the sidewall and the plug; a bottom surface of the top wall defining a roof of the annular space, the bottom surface of the top wall having an undulating contour extending circumferentially, the bottom surface having a plurality of low points and a plurality of high points resulting from the undulating contour; and at each low point, a lug formed into the bottom surface of the top wall and comprising a bottom surface, the bottom surfaces of the lugs collectively defining a seating plane that is substantially perpendicular to the axis. 
     In a still further aspect, the invention can be a closure having a saddle-shaped top wall having a top surface with undulating concave and convex surfaces. 
     In yet another aspect, the invention can be a closure for a container comprising a body having a top wall and a sidewall extending axially therefrom. The closure may define an interior cavity configured for receiving the neck portion of a container. The closure may further include a sealing tube configured to engage the neck portion of the container for forming a liquid seal. A plurality of radially-extending struts may be provided that span between the sidewall and sealing tube and which are configured to engage the neck portion of the container. The supporting struts collectively define a common seating plane and may structurally reinforce the closure. The closure may further include lugs disposed along the seating plane. 
     The foregoing and other aspects of a container formed according to principles of the present invention are further described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features, and advantages of the invention will be apparent from the following more detailed description of certain embodiments of the invention and as illustrated in the accompanying drawings in which: 
         FIG. 1  is a perspective view of a closure for a container according to an embodiment of the present invention; 
         FIG. 2  is a first side view showing a convex portion of the top wall of the closure of  FIG. 1 ; 
         FIG. 3  is a second side view thereof showing a concave portion of the top wall of the closure of  FIG. 1 ; 
         FIG. 4  is a bottom view of the closure of  FIG. 1 ; 
         FIG. 5  is a side cross-sectional view taken along plane V-V in  FIG. 4 ; 
         FIG. 6  is a side cross-sectional view taken along plane VI-VI in  FIG. 4 ; 
         FIG. 7  is a detailed view of area VII of  FIG. 6 , showing a portion of a sealing tube and a stop lug of the closure of  FIG. 1 ; 
         FIG. 8  is transverse cross-sectional view of the closure of  FIG. 1  fully seated on a container according to an embodiment of the present invention; 
         FIG. 9  is a transverse cross-sectional side view of the container of  FIG. 8  with the closure removed; and 
         FIG. 10  is a detailed view of area X of  FIG. 6 , showing a portion of a sealing tube and stop lug of the closure of  FIG. 1 . 
     
    
    
     All drawings are schematic and not actual physical representations of the articles, components or systems described herein, and are further not drawn to scale. The drawings should be interpreted accordingly. 
     DETAILED DESCRIPTION 
     The following description, which is illustrative of certain embodiments according to principles of the present invention, is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of embodiments of the invention disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “attached,” “affixed,” “connected,” and “interconnected” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. Moreover, the features and benefits of the invention are illustrated by reference to the preferred embodiments. Accordingly, the invention expressly should not be limited to such preferred embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features; the scope of the invention being defined by the claims appended hereto. 
     Referring first to  FIGS. 1-3  concurrently, a closure  20  according to one embodiment of the present invention is exemplified. The closure  20  is designed to be secured to a container, and more preferably a liquid filled container. The closure  20  may be formed of any suitable material, including without limitation a plastic material, such as polypropylene, polyethylene, and/or combinations thereof. Of course, other plastics can be used to form the closure as is known in the art. In one preferred embodiment, the material of construction is polypropylene. The material selected for the closure  20  may further be at least partially resilient to form a liquid seal with the container, as further described herein. The closure  20  may be fabricated by any suitable fabrication technique used in the art, including for example, without limitation, compression or injection molding. 
     The closure  20  includes a body  21  having a radially-extending top wall  22  and an annular skirt or sidewall  24  extending from the top wall  22  in an axial direction. More specifically, the annular sidewall  24  extends from the top wall  22 , along the periphery of the top wall  22 , thereby circumferentially surrounding the central axis CA of the closure  20  and forming an interior cavity  33 . A circumferentially-extending upper edge  25  is formed at the junction of the sidewall  24  and the top wall  22 , thereby delineating a peripheral edge of the top wall  22 . In the illustrated embodiment, the sidewall  24  may include a lower portion that gradually flares outward from the central axis CA. The exact configuration of the sidewall  24 , however, is not limiting of the present invention. The sidewall  22  may be provided in a wide variety of suitable configurations to match the aesthetic configuration of the corresponding container, which may also be of any suitable configuration. 
     The bottom  23  end of the body  21  is open, thereby forming a passageway into the interior cavity  33  through which a neck portion  41  of a container  40  (see, e.g.  FIG. 8 ) can be inserted into the closure  20 . The top end of the body  21  is closed so that the closure  20  can be used to seal an opening of the neck portion  41  of the container  40  when secured thereto. Of course, in certain embodiments, the close top end of the body  21  may be adapted so that liquid from the container can be dispensed via the closure  20  in a controlled manner. 
     For example, in the illustrated embodiment, the top wall  22  includes an aperture  26  for dispensing liquid from the container  40  when the closure  20  is mounted to the container. The aperture  26  may be of any suitable configuration or structure. In the illustrated embodiment, the aperture  26  is defined by a cylindrical spout  126  that extends axially upward from a top surface  130  ( FIG. 1 ) of the top wall  22 . The cylindrical spoutl  26  (and aperture  26 ) may be used alone for dispensing liquid or may be configured to be operably coupled to a slidable push-pull type nozzle (not shown), which can be slid between an open position in which liquid from the container can be dispensed via the aperture  26  and a closed position in which the aperture  26  is sealed. Such push-pull type nozzles are known in the art. In other embodiments, various other types and shapes of apertures and nozzle structures may be provided. 
     Alternatively, the top end of the closure  20  may be completely closed without any apertures or openings formed therein. Accordingly, the invention is not limited by any particular shape or type of liquid dispensing means that may be furnished with the closure  20 . 
     Referring now to  FIGS. 4-6  concurrently, as mentioned above, the top wall  22  and the sidewall  24  of the closure  20  define an interior cavity  33  for receiving the neck portion  41  of container  40  (see, e.g.  FIG. 8 ). The closure  20  further includes a plug  90  that circumferentially surrounds the central axis CA. When the closure  20  is mounted to the container  40 , the plug  90  forms a primary circumferential liquid seal via surface contact between an annular axial exterior surface  91  of the plug  90  and an annular axial interior surface  36  of the neck portion  41  of the container  40 . The plug  90  is a cylindrical structure that extends axially downward from the top wall  22 . Depending on the type of closure  20  desired, the plug  90  may be a solid cylinder or a tubular cylinder. 
     In the exemplified embodiment, the plug  90  is in the form of a cylindrically shaped annular sealing tube  27 , which is disposed within interior cavity  33  of the body  21  and extends axially downward from the underside  152  of the top wall  22 . The sealing tube  27  engages the neck portion  41  of the container  40  when the closure  20  is threaded onto the container  40  to establish the hermetic seal. Preferably, the sealing tube  27  is configured and adapted to provide a relatively snug frictional fit between the container neck portion  41  and the tube  27 . To this extent, the sealing tube  27  includes a radially outward facing annular axial sealing surface  35  (see, e.g.  FIGS. 5 and 7 ) configured for engaging a complementary radially inward facing annular axial sealing surface  36  (see, e.g.  FIGS. 8 and 9 ) on the container neck portion  41 . The sealing tube  27  is preferably structured to be at least partially resilient and deformable when engaged with the neck portion  41  of the container  40  to enhance the tightness of the liquid seal. 
     Referring now to  FIGS. 5 and 6  concurrently, the sidewall  24  circumferentially surrounds the sealing tube  27  (both of which are concentric to the central axis CA) in a spaced apart manner so that an annular space  28  is formed within the interior cavity  33 . The annular space  28  is formed below the top wall  22  and between the sidewall  24  and the sealing tube  27 . More specifically, the annular space  28  is formed between the radially outward facing annular axial sealing surface (also referred to as an exterior axial annular surface)  35  of the sealing tube  27  and the interior axial annular surface  29  of the sidewall  24 . The annular space  28  has an open bottom end so that the annular space  28  is in spatial communication with the remainder of the interior cavity  33  and a closed top end, which is delimited by a bottom surface  52  of the top wall  22 . The bottom surface  52  is a section of the underside  152  of the top wall  22  that forms a roof of the annular space  28 . Thus, in the illustrated embodiment, the bottom surface  152  is an annular surface. The annular space  28  is configured for receiving and securing the upper part of the container neck portion  41  when the closure  20  is fully seated on the container  40 , as further described herein. 
     In some embodiments, the closure  20  may be removably secured to the container  40  via a conventional threaded connection. Accordingly, the closure  20  may include a generally cylindrically-shaped coupling portion  34 , which in turn included an internal thread finish configured for threadily engaging a corresponding external thread finish provided on the container neck portion  41 . In one embodiment, with reference to  FIGS. 5 ,  8 , and  9 , one or more internal threads (or thread segments)  30  are provided on the interior axial surface  29  of the closure  20  on the coupling portion  34  that threadily mate with complementary external threads (or thread segments)  31  formed on the axial exterior surface  32  of the container neck portion  41 . Of course, any suitable conventional thread finish may be used for the closure  20  and the container  40  as desired. In one example, without limitation, a finish of 28/400 may be used. 
     In other possible embodiments, the closure  20  may be permanently or semi-permanently attached to the container  40  via other suitable attachment means used in the art, including without limitation a snap-fit, friction fit, adhesives, heat welded seams, and/or combinations thereof. Stated simply, the invention is not limited to threaded attachment between the container  40  and the closure  20  in all embodiments. 
     Referring again to  FIGS. 1-3  and  5 - 8  concurrently, the top wall  22  of the closure  20  has a bottom surface  52  (and top surface  130 ) that is not substantially planar (or flat) as is the case with prior known closure embodiments. Instead, in the exemplified embodiment, the top wall  22  of the closure  20  has a saddle-shaped top surface  130  that includes a combination of undulating surfaces extending radially outwards from the central axis CA of the closure  20 . When viewed from the sides of the closure  20 , the top surface  130  of the top wall  22  includes two convex surface sections  50  disposed on opposite portions of the top wall  22  (see  FIGS. 2 and 6 ) and two adjacent concave surface sections  51  (see, e.g.  FIGS. 3 and 5 ) disposed on opposite portions of the top. Accordingly, the top surface  130  of the top wall  22  has a shape that circumferentially alternates between convex surface sections  50  and concave surface sections  51 . In one possible embodiment, as illustrated, a gradual transition may be provided between the convex and concave surface sections  50 ,  51  such that the upper edge  25  extends circumferentially in a manner that defines an undulating sinusoidal shape when the closure  20  is viewed from the side and rotated 360 degrees around. It should be noted that in the exemplified embodiment, the bottom surface  52  of the top wall  22  has an undulating contour that follows the undulating contour of the top surface  130 . Thus, the above description is applicable to the bottom surface  152  of the top wall  122 , with the terms convex and concave being alternated of course. 
     The convex surface sections  50  define two peaks or high points HP disposed at diametrically-opposed points on the upper edge  25  of the closure  20  located along a first transverse axis TA 1  across the top wall  22  (see  FIGS. 2 and 4 ). The first transverse axis TA 1  is parallel with and includes the central axis CA. Contrastingly, the concave surface sections  51  define two valleys or low points LP disposed at diametrically-opposed points on the upper edge  25  located along a second transverse axis TA 2  on the top wall  22  (see  FIGS. 3 and 4 ). The second transverse axis TA 2  is also parallel with and includes the central axis CA. The first and second transverse axes Ta 1 , TA 2  are orthogonal to one another (i.e., oriented a circumferential 90 degree angle to each other) in this embodiment. 
     As best shown in  FIGS. 5 and 6 , the top wall  22  includes the bottom surface  52  (which acts as an interior radial landing surface) disposed within annular space  28  on the underside  152  of the top wall  22  as mentioned above. The bottom surface  52  has an undulating contour that follows the corresponding rising and falling contour of the convex and concave surface sections  50 ,  51  of the top surface  130 , but internally (see, e.g.  FIGS. 2 and 3 ). The undulating contour of the bottom surface  52  of the top wall  22  also generally follows the pattern of the upper edge  25 . When the closure  20  is screwed onto the threaded neck portion  41  of the container  40 , however, the flat upward facing radial rim surface  43  defined by the neck rim  42  of the neck portion  41  (see  FIG. 8 ) at the opening  44  of the container  40  would be prevented from squarely seating on and abutting corresponding sections of the closure&#39;s interior radial landing surface  52 . This is desired to properly balance and seat the closure on the container for establishing a uniform and tight liquid seal between the cylindrical sealing tube  27  and the container neck portion  41  as already described herein. Thought of another way, the bottom surface  52  of the top wall  22  is not coplanar with a reference plane that is substantially parallel to a seating plane formed by the rim surface  43 . Thus, the bottom surface  52  rest atop the rim surface  43  with any rigidity or structural integrity. 
     To partially address the foregoing contour mismatch between the container rim  42  and the bottom surface  52  of the top wall  22 , a laterally broadened and elongated stop lug  60  is provided at each of the two low points LP as shown in  FIGS. 3 ,  4 ,  6  and  7 . In one embodiment, the stop lugs  60  may be formed as slightly raised portions of the bottom surface  52  on the underside  152  of the top wall  22 . In an alternative embodiment, portions of the bottom surface  52  itself (at the low points LP) may simply form the lugs without any protrusions or manipulation of the undulating contour of the bottom surface  52 . The stop lugs  60  are configured and adapted to provide a relatively flat seating surface  61  for engaging the upward facing flat radial rim surface  43  on the rim  42  of container neck portion  41  when closure  20  is fully seated on the container. Thought of more broadly, the flat seating surface  61  (which are the bottom surfaces) of the lugs  60  lie within the reference plane that is substantially parallel with the seating plane formed by the rim surface  43 . 
     In the illustrated embodiment, the stop lugs  60  are disposed on diametrically-opposed portions of the closure  20  and angularly spaced 180 degrees apart. The stop lugs  60  are preferably elongated in a lateral (or circumferential) direction perpendicular to the closure central axis CA, as best shown in  FIGS. 3 and 4 , and have a width WL. The width WL of the stop lugs  60  is preferably at least twice the width WS of the supporting struts  70  (described below), and more preferably at least four times larger than the width WS. The lugs  60  each bridge one of the valleys or low points LP on the closure  20 . The stop lugs  60  are thus intended to assist in balancing the closure  20  on the container neck portion  41  and preventing over-torqueing of the closure  20  onto the container  40 , especially by automated equipment on a liquid fill processing line. 
     It has been discovered through trial testing by the inventors, however, that the stop lugs  60  alone do not completely resolve the contour mismatch problems associated with the undulating contour of the bottom surface  52  of the closure&#39;s top wall  22 . When the closure  20  is threaded onto the neck portion  41  of the container  40 , the stop lugs  60  initially engage the upward facing radial rim surface  43  defined on the container neck portion  41 , thereby resisting the axial forces applied to the closure  20  during tightening of the closure  20  onto the container  40 . The stop lugs  60  only provide support for the closure  20  at two positions angularly spaced 180 degrees apart, thereby leaving other circumferential portions of the closure unsupported to resist the axial tightening forces. As a result, it has been discovered that the lower or bottom portions of the sidewall  24  that are located 90 degrees apart from the stop lugs  60  (which correspond to the closure high points HP (see  FIGS. 2-4 )) tend to pinch and deflect radially inwards as torque is applied to the closure  20 , despite the engagement by the bottom surfaces  61  of the lugs  60 . This pinching and deflection distorts the closure  20  and creates ovality in shape, which in turn results in leakage at the primary seal formed between the plug  90  and the neck portion  41  (described above). 
     Referring now to  FIGS. 2-5 , the closure  20  preferably further includes a plurality of closure supporting struts  70  to augment (or replace) the stop lugs  60  for eliminating or reducing the leakage problem at the primary seal. In one possible embodiment, as shown, the supporting struts  70  are disposed in the interior cavity  33  and are arranged in a circumferentially spaced apart manner about the central axis CA between the stop lugs  60 . Preferably, the supporting struts  70  are evenly/uniformly spaced apart from one another in the circumferential zones created between the lugs  60 . The supporting struts  70  are disposed in and span radially across the annular space  28 , as best shown in  FIGS. 4 and 5 . Preferably, the struts  70  are rigidly attached along three of their sides to the closure  20 . The struts  70  are each attached to both the interior axial surface  29  of the sidewall  24  along a first vertical side  73  and the annular axial sealing surface  35  of the sealing tube  27  along an opposite second vertical side  74 . The top of each supporting strut  70  is also attached to the bottom surface  52  of the underside  152  of the top wall  22  along a third horizontal side or upper end  71  of the strut  70 . However, in alternative embodiments, the struts  70  may be attached to only of the aforementioned surfaces and/or structures if desired. 
     With continuing reference to  FIGS. 2-5 , the supporting struts  70 , in one possible embodiment, preferably each have the same radial or lateral cross-sectional shape as will be apparent by particular reference to  FIG. 4 , which shows the underside  152  of the closure  20 . Any suitable cross-sectional shape may, however, be provided for supporting struts  70 . In some embodiments, supporting struts  70  may have a generally rectangular radial/lateral cross section or be slightly wedge-shaped as shown in  FIG. 4 . so as to have a gradually increasing horizontal width W traveling radially outwards from the closure central axis CA. The supporting struts  70  preferably have radial depth D that is coextensive with the depth or width of annular space  28 , as best shown in  FIGS. 5 and 10 . 
     Referring to  FIGS. 2-3 ,  5 , and  10 , the supporting struts  70  have varying heights H (measures from their bottom surfaces  72  to the bottom surface  52  of the top wall  22 ) since the upper end  71  of each strut is preferably attached to the bottom surface  52  of the underside  152  of the top wall  22 . As best shown in  FIGS. 2 and 3 , therefore, the height of each strut H will vary with respect to the undulating contour of the bottom surface  52  that follows the undulating contour of the top surface  130  (and upper edge  25 ) of the top wall  22 , as already described herein. In order to ensure that each supporting strut  70  squarely rests on the flat upward facing radial rim surface  43  on the rim  42  of the container neck portion  41  (see  FIG. 9 ) when the closure  20  is fully seated on the container  40 , the bottom surfaces  72  of the struts  70  preferably lie within (i.e., collectively form) an imaginary reference plane P which is substantially parallel with the seating plane formed by the rim surface  43 . In the illustrated embodiment, this imaginary reference plane is a horizontal seating pane P that is substantially perpendicular to the central axis CA, as best shown in  FIGS. 2 ,  3 , and  8 . This horizontal seating plane P is, therefore, coplanar with the seating plane formed by the radial surface  43  of container neck portion  41  when the closure  20  is fully seated on the container  40  (see  FIG. 8 ). Preferably, the bottom surfaces  72  of the supporting struts  70  and the bottom surfaces  61  of stop lugs  60  all therefore lie within and collectively form the same seating plane P. As a result, the bottom surfaces  61  of the lugs  60  and the bottom surfaces  72  of the struts  70  simultaneously come into surface contact with the rim surface  43  of the container neck portion  41  (allowing for fabrication dimensional tolerances) to balance the closure  20  and axial forces imparted to the closure  20  via the neck portion  41  when the closure  20  is threaded onto the container  40 . Preferably, the bottom surfaces  61  of the lugs  60  and the bottom surfaces  72  of the struts  70  are flat surfaces. The invention, however, is not so limited in all embodiments. 
     Referring still to  FIGS. 2-5 , at least two supporting struts  70  are provided that are angularly spaced at 90 degrees apart from the stop lugs  60 , as best shown in  FIG. 4 , to coincide with the location of the high points HP. In conjunction with the stop lugs  60 , this provides four contact points each at 90 degrees apart between the closure  20  and the upward facing radial surface  43  at the rim  42  of the container neck portion  41 . Advantageously, the combination of the supporting struts  70  and the stop lugs  60  balances and evenly distributes the axial forces exerted on the closure  20  when it is screwed onto the container neck portion  14 . In addition, the supporting struts  70  radially reinforce the closure  20  and the sealing tube  27  to prevent or minimize lateral distortion and ovality. These combined effects eliminate or minimize leakage at the primary plug seal  90 . 
     In a preferred embodiment, at least six supporting struts  70  are provided which may be angularly spaced at even intervals of 45 degrees apart between stop lugs  60  as shown in  FIG. 4 . These additional contact points between the neck portion  41  of the container  40  and the closure  20  further enhance the liquid tight seal. In a preferred embodiment, the supporting struts  70  may be molded as an integral part of the closure  20  during the closure molding process. 
     It will be appreciated that a closure for a container formed according to principles of the present invention may have a top or upper radial surface with various irregular or non-uniform shapes other than the saddle-shape disclosed herein so long as a common seating plane is established by the bottom surfaces of the supporting struts and/or the bottom surfaces of the lugs. Such alternate embodiments contemplated may include, for example, more angularly shaped surfaces disposed and intersecting at varying angles with distinct transitions rather than smoothly contoured and transitioning surfaces as disclosed herein. Accordingly, the invention is not limited to the top surface shape disclosed herein or any particular shapes. 
     It will be understood that while the invention has been described in conjunction with specific embodiments thereof, the foregoing description and examples are intended to illustrate, but not limit the scope of the invention. Other aspects, advantages and modifications will be apparent to those skilled in the art to which the invention pertains, and these aspects and modifications are within the scope of the invention and described and claimed herein.