Abstract:
A linerless closure of one-piece integrally molded plastic construction includes a base wall and a cylindrical skirt for attaching the closure to a container neck finish. First and second circumferentially continuous annular walls extend from the base wall at positions radially inward from the skirt. The first and second annular walls are spaced from each other to receive an end portion of the container neck finish when the closure is applied to the neck finish. At least one of the annular walls has a circumferentially continuous annular projection extending toward the opposing annular wall. The annular projection is axially flexible for bending and folding toward the base wall and toward the at least one annular wall in sealing engagement with the end portion of the container neck finish when such end portion is received between the annular walls.

Description:
The present disclosure relates to linerless closures, and to pressurized packages containing such closures. 
   BACKGROUND AND SUMMARY OF THE DISCLOSURE 
   It is conventional in the packaging field to provide pressurized closure and container packages, such as cold soft drink packages, having a flexible resilient liner for sealing engagement with at least one sealing surface on the container neck finish. Linerless closures have been proposed for non-pressurized packages to eliminate the expense of providing a sealing liner on the closure. However, linerless closures have not been as successful as desired in pressurized package applications, ranging from bottled water packages having an internal pressure of about 10 psi to cold soft drink packages having an internal pressure of about 75 psi at room temperature. Difficulties are encountered in manufacturing the closure with sufficient accuracy to maintain sealing contact with the container neck finish, particularly in applications involving molded plastic containers. It is a general object of the present disclosure to provide a linerless closure, and to provide a package embodying such a closure, that is adapted to achieve and maintain sealing engagement with the container neck finish in pressurized package applications over normal manufacturing tolerance variations on the closure and the container neck finish. 
   The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other. 
   A linerless closure of one-piece integrally molded plastic construction, in accordance with one aspect of the present disclosure, includes a base wall and a cylindrical skirt for attaching the closure to a container neck finish. First and second circumferentially continuous annular walls extend from the base wall at positions radially inward from the skirt. The first and second annular walls are spaced from each other to receive an end portion of the container neck finish when the closure is applied to the neck finish. At least one of the annular walls has a circumferentially continuous annular projection extending toward the opposing annular wall. The annular projection is axially flexible for bending and folding toward the base wall and toward the at least one annular wall in sealing engagement with the end portion of the container neck finish when such end portion is received between the annular walls. 
   In exemplary preferred embodiments of the disclosure, the base wall has a central portion with a first thickness, a first peripheral portion contiguous with the central portion and having a second thickness greater than the first thickness, and a second peripheral portion between the first peripheral portion and the skirt and having a third thickness greater than the second thickness. The first annular wall extends from the base wall at a juncture of the central and first peripheral portions of the base wall. The second annular wall extends from the base wall at a juncture of the first and second peripheral portions of the base wall. In some preferred embodiments of the disclosure, both of the annular walls have circumferentially continuous axially flexible annular projections that extend toward the opposing wall, most preferably in radial alignment with each other. In another preferred embodiment of the disclosure, the radially inner annular wall is contoured for plug-sealing engagement with the inside surface of the container neck finish when the closure is attached to the container neck finish. In the exemplary preferred embodiments of the disclosure, the annular projections are wedge-shaped in radial cross section. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The disclosure, together with additional objects, features, advantages and aspects thereof, will best be understood from the following description, the appended claims and the accompanying drawings, in which: 
       FIG. 1  is a fragmentary sectional view of a package in accordance with one exemplary embodiment of the disclosure; 
       FIG. 2  is a sectional view on an enlarged scale of the portion of  FIG. 1  within the area  2 ; 
       FIG. 3  is a diametric sectional view of the closure in  FIG. 1 ; 
       FIG. 4  is a sectional view on an enlarged scale of the portion of  FIG. 3  within the area  4 ; and 
       FIGS. 5 and 6  are fragmentary sectional views that are similar to  FIG. 4  but illustrate respective alternative embodiments of the disclosure. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  illustrates a package  20  in accordance with an exemplary embodiment of the present disclosure. Package  20  includes a closure  22  applied to a container  24 . Container  24  has a body from which a cylindrical neck finish  28  extends, typically although not necessarily coaxially with the container body. Neck finish  28  includes an end forming an open mouth with inner and outer cylindrical surfaces that nominally are concentric with each other. One or more external thread segments  30  are provided on neck finish  28  at a position spaced from the mouth of the neck finish. There may or may not be cooperating tamper-indicating structure on the closure and container, of which one type is illustrated in  FIG. 1 . Package  20  is filled with product  34  and has an internal pressure of at least 10 psi at room temperature. 
   Referring to  FIGS. 1-4 , closure  22  includes a base wall  36  and a peripheral skirt  38 . Peripheral skirt  38  is cylindrical and has one or more internal thread segments  40  for engagement with external thread segments  30  ( FIG. 1 ) on container neck finish  28 . Base wall  36  preferably has a central portion  42  with a first axial thickness  44  ( FIG. 4 ). (Directional words such as “axial” and “radial” are employed by way of description and not limitation with respect to the central axis of container neck finish  28  or closure skirt  38  as appropriate. Directional words such as “upper” and “lower” are employed by way of description and not limitation with respect to the upright orientations of the package and closure illustrated in the drawings.) A first annular peripheral portion  46  of base wall  36  is contiguous with central portion  42  and preferably has a second axial thickness  48  that is greater than thickness  44  of central portion  42 . A second annular peripheral portion  50  of base wall  36  integrally connects first peripheral portion  46  with skirt  38 , and preferably has an axial thickness  52  that is greater than thickness  48  of first peripheral portion  46 . The upper or outer surface of base wall  36  preferably, but not necessarily, is smooth without undulations or recesses. 
   A first annular wall  54  extends from the juncture of base wall central portion  42  and first peripheral portion  46 . In the embodiment of  FIGS. 1-4  (and the embodiment of  FIG. 5 ), first annular wall  54  preferably extends at an angle axially away from base wall  36  and radially toward skirt  38 . (It will be recognized that all geometries and dimensions provided in this disclosure are nominal geometries and dimensions of the closure as designed. In actual practice these geometries and dimensions may vary somewhat due to tolerance variations in the mold in which the closure is fabricated, and/or due to distortions in the closure geometry as the closure is stripped from the mold.) First annular wall  54  preferably has a radially inwardly facing surface  56  that is nominally conical in geometry, extending axially away from base wall  36  and radially toward skirt  38 . By way of example only, surface  56  may be at a nominal angle of 30° to the axis of closure skirt  38 . The radially outwardly facing surface  58  of first wall  54  preferably is cylindrical and nominally coaxial with skirt  38 . A second annular wall  60  extends away from base wall  36  from a juncture of first and second peripheral base wall portions  46 ,  50 . Second annular wall  60  preferably has a radially inwardly facing surface  62  and a radially outwardly facing surface  64 , both of which are nominally cylindrical, coaxial with each other and coaxial with skirt  38 . Annular walls  54 ,  60  are circumferentially continuous. Annular walls  54 ,  60  preferably have respective ends  66 ,  68  spaced from base wall  36  and lying in a plane nominally perpendicular to the axis of skirt  38 . Wall ends  66 , 68  preferably are flat. 
   A pair of flexible lips or projections  70 ,  72  extend from first and second annular walls  54 ,  60 . Projections  70 ,  72  are circumferentially continuous, and preferably are radially opposed to each other, although axially offset projections can be employed if desired. Projections  70 ,  72  preferably are nominally wedge-shaped in radial cross section, and have respective sharp edges  74 ,  76  that are radially opposed to each other in a plane nominally perpendicular to the axis of skirt  38 . In the embodiment of  FIGS. 1-4 , projections  70 ,  72  are mirror images of each other in radial cross section. Projection  70  has an annular undersurface  78  facing away from base wall  36  and an annular upper surface  80  facing in the direction of base wall  36 . Likewise, projection  72  has an annular undersurface  82  facing away from base wall  36  and an annular upper surface  84  facing in the direction of base wall  36 . Undersurfaces  78 ,  82 , as designed, nominally are flat and coplanar with each other in a plane perpendicular to the axis of skirt  38 . Flat annular undersurfaces  78 ,  82  contribute to the flexibility of projections  70 ,  72  to ensure that the projections will fold into sealing engagement with the container neck finish ( FIG. 2 ). Upper surfaces  80 ,  84  preferably are conical and at respective angles to undersurfaces  78 ,  82 , most preferably identical angles in the embodiment of  FIGS. 1-4 . Upper surfaces  80 ,  84  are at nominal angles of 35° to undersurfaces  78 ,  82  in the embodiment of  FIGS. 1-4 . 
   When closure  22  is applied to container neck finish  28 , projections  70 ,  72  respectively engage the inside and outside surfaces of the neck finish around the container mouth. Projections  70 ,  72  are bent and folded upwardly along the respective neck finish surfaces as illustrated in  FIG. 2 . Closure  22  preferably is tightened onto neck finish  28  sufficiently to bring the axially facing undersurface  86  of base wall portion  46 , between annular walls  54 ,  60 , into opposed sealing engagement with the axially facing surface  88  of neck finish  28 . Thus, neck finish  28  is sealed by engagement not only with end surface  88 , but also by engagement of projections  70 ,  72  with the inside and outside surfaces of the neck finish around the container mouth. Annular undersurface  86 , which extends between walls  54 ,  60 , preferably nominally is flat and perpendicular to the axis of the closure skirt. 
     FIGS. 5 and 6  illustrate respective modified embodiments of the disclosure. Reference numerals employed in  FIGS. 5 and 6  that are identical to those employed in  FIGS. 1-4  indicate correspondingly identical or related components. 
   The closure  90  in  FIG. 5  differs from closure  22  in  FIGS. 1-4  primarily in that the upper surface  92  of projection  70  is at a greater angle to undersurface  78  than is upper surface  84  of projection  72 . Projections  70 ,  72  thus are not mirror images of each other in the embodiment of FIG.  5 . The angle of surface  92  to surface  78  in  FIG. 5  preferably is such that surface  92  nominally is parallel to surface  56 . In the embodiment of  FIG. 5 , projection  70  is stiffer than projection  72 , and the closure is easier to strip from the forming mold. 
     FIG. 6  illustrates a closure  94  in which the first annular wall  96  is nominally cylindrical, rather than angled to base wall  36  as in the embodiments of  FIGS. 1-5 . Cylindrical annular wall  96  is circumferentially continuous and extends from the juncture of base wall portions  42 , 46  as in the embodiments of  FIGS. 1-5 , but nominally is coaxial with and parallel to skirt  38 . Annular wall  96  has a radially outer surface with a cylindrical surface portion  98  adjacent to base wall  36  and an inwardly sloping conical surface portion  100  remote from base wall  36 . Wall surface portion  98  preferably is nominally cylindrical, coaxial with skirt  38  and coaxial with inner cylindrical surface  102  of wall  96 . Projection  72  on annular wall  60  preferably is in radially outward alignment with conical surface portion  100  of wall  96 . When closure  94  is applied to a container neck finish, wall  96  is brought into surface-to-surface plug-sealing engagement with the inside surface of the container neck finish, while projection  72  on wall  60  folds upwardly and outwardly in resilient sealing engagement with the outer surface of the container neck finish as in the prior embodiments. The embodiment of  FIG. 6  is easily stripped from its forming mold. 
   The closure of the present disclosure may be molded of any suitable plastic material such as polypropylene. Container  24  is illustrated as being of plastic construction in  FIGS. 1 and 2 , which is preferred, but could be of other suitable construction such as glass. 
   There thus have been disclosed a closure and package that fully satisfy all of the objects and aims previously set forth. The closure of the present disclosure is able to maintain sealing engagement with the container neck finish of a pressurized package under a wide variety of conditions and environments. The disclosure has been presented in conjunction with several presently preferred embodiments, and a number of modifications and variations have been discussed. Other modifications and variations readily will suggest themselves to persons of ordinary skill in the art in view of the foregoing discussion. The disclosure is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.