Threaded closure for pressurized containers

A threaded closure for pressurized containers, typically for carbonated beverages is disclosed. The closure includes a deformable liner of non-vinyl polymer which is cold formed in the closure using known techniques in such manner that the liner physically bonds to the inner surface of the end wall of the closure to be retained thereby in the absence of a peripheral lip or projections on the inner surface of the end wall of the closure. The closure itself may be either injection molded or compression molded. The usual tamper indicating ring is formed to include frangible bridge members either by molding or a separate slitting operation. The pivotally mounted tabs for separating the tamper-indicating ring are sufficiently rigid to avoid flexing at points other than at an outer edge hinge axis where pivoting is possible only to a limited degree, thus assuring the severing of the frangible bridge members at an early stage of opening of the closure.

BACKGROUND OF THE INVENTION
 This invention relates generally to the field of threaded closures for
 containers, and more particularly to synthetic resinous closures of
 relatively small diameter employed to seal containers of pressurized
 contents, typically soft drinks, beer and other carbonated comestibles.
 Traditionally, such containers have been sealed using metallic caps
 commonly referred to as crown closures requiring the use of a tool for
 removal. Over the past fifteen to twenty years, such closures have been
 almost completely replaced by a synthetic resinous closure either
 injection molded, or, more commonly, compression molded. Such closures are
 usually provided with a tamper-evident ring which depends from the lower
 edge of the cylindrical side wall of the closure, and is interconnected to
 said edge by frangible bridges formed during the molding operation, or by
 a separate slitting operation. Annual production of said closures
 surpasses that of other types of closures, and, not surprisingly, the art
 relating to such closures is in a highly developed state.
 Although synthetic resinous closures of this type have many advantages,
 including the ability to be removed without the use of a tool, and the
 ability to reseal the container where all of the contents are not consumed
 upon first opening, they do present significant problems during
 manufacture.
 One of the problems concerns the formation of a sealing liner beneath the
 inner surface of the end wall of the closure. The material used in forming
 the closure, while possessing a degree of resilience, is normally not
 possessed of adequate cold flow properties to form a gas tight seal
 against the mouth of the container neck or finish. This function is
 normally provided by forming a liner of softer synthetic material in situ
 using the closure as a female part of the mold in conjunction with a
 reciprocating male part which flattens and shapes a measured quantity of
 material. The closure is provided with an inwardly projecting lip which is
 of lesser diameter than the internal thread diameter forming an undercut
 or recess which shapes the rim of the flattened seal. That portion of the
 rim of the seal disposed immediately inwardly of the lip engages the end
 surface of the mouth of the finish to effect a gas tight seal. It is usual
 to form that portion to a slightly thicker cross section for greater
 resiliency. This construction does not permit the formation of a sealing
 effect which extends outwardly beyond the inner edge of the lip.
 A more serious problem lies in the provision of frangible ribs or bridges
 which interconnect the lower edge of the side wall or skirt of the closure
 with the tamper-indicating band or ring. The bridges must be sufficiently
 strong so as to avoid breaking when the closures are installed, either by
 threading or pressing the closures into position, and yet be capable of
 readily fracturing when the closure is unthreaded. To this end, designs
 have included the provision of some bridge members which are stronger than
 other bridge members and are positioned in specific locations, this
 construction being partially successful when the tamper-evident ring is
 split and remains attached to the skirt during removal of the closure.
 Other constructions provide for a camming action utilizing inclined
 surfaces at the lower edge of the skirt and the upper edge of the
 tamper-indicating ring.
 The most common construction used for fracturing the bridges is the use of
 flexible wings or tabs. One form uses tabs which engage the outer surface
 of the finish to prevent rotation of the ring relative to the skirt. More
 commonly, the tabs are pivoted about an axis normal to the axis of the
 closure and have free ends which engage beneath a radially projecting bead
 on the outer surface of the container finish. The tabs are not only
 pivoted relative to the inner surface of the ring, but are flexible as
 well to permit easy removal without damage from a forming mold. The
 relatively thin cross section required to produce this flexibility has an
 adverse result in that the tabs are occasionally not sufficiently rigid to
 assure prompt breakage of the bridges when the closure is unthreaded. This
 problem is accommodated by the provision of a radially inwardly extending
 band on the inner surface of the ring against which the tabs are engaged
 after being folded through approximately 135 degrees. This engagement
 reduces the effective diameter of the bead on the tamper-indicating ring
 to less than that of the corresponding bead on the outer surface of the
 container, so that it cannot pass the bead on the container, and continued
 unthreading of the closure serves to break the bridges. The use of this
 construction is almost mandatory where the bridges are of unequal
 strength. However, this construction in its so-called second mode of
 operation requires a substantial degree of unthreading of the closure
 before the bridges are broken, and no substantial leverage is obtained.
 SUMMARY OF THE INVENTION
 Briefly stated, the invention contemplates the provision of an improved
 closure of the type described in which the above-mentioned problems have
 been either eliminated or substantially ameliorated.
 At the upper part of the closure, the seal retaining lip forming an
 undercut portion which retains the seal in position has been eliminated
 through the use of superior seal-forming materials permitting the seal to
 be of greater diameter than heretofore possible to present a greater
 sealing surface to the peripheral edge of the mouth of the closure. The
 seal, once cold formed within the closure, bonds to the inner surface of
 the end wall thereof without the necessity of interlocking projections or
 surfaces, and is incapable of relative rotation therebetween.
 At the opposite end of the closure, the above-described relatively
 complicated flexible tab construction is substituted by hingedly
 interconnected tabs which are of sufficient cross section to preclude
 flexing, so as to assure that the free ends thereof will exert an
 unyielding leveraged force to the undersurface of the container bead to
 positively fracture the tamper-indicating ring bridges, without the
 necessity of providing a secondary mode for that purpose. The
 cross-sectional shape of the tabs is such that they can be readily removed
 from a mold without damage or difficulty.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT
 In accordance with the invention, the device, generally indicated by
 reference character 10 is of conventional configuration, including an end
 wall 11, a side wall or skirt 12, a tamper-indicating ring 13
 interconnected by frangible bridges 14, and a resilient liner 15. Most
 conveniently, the device, exclusive of the liner 15, is either compression
 molded or insert molded from polypropylene or synthetic resinous materials
 having similar properties. Using techniques known in the art, the liner 15
 is formed by depositing a measured quantity of polymeric material in a
 recess in the inner surface of the end wall.
 The end wall 11 is bounded by an outer surface 20 and an inner surface 21
 which defines a recess 22 in which the liner 15 is formed. It meets with
 the side wall 12 at a rounded edge 24. The side wall 12 is bounded by an
 outer surface 25, preferably having finger-engaging striations 26 thereon,
 as well as an inner surface 27 having an upper threaded portion 28. The
 tamper-indicating ring 13 is interconnected to the lower edge of the side
 wall 12 by frangible bridges 40. The ring 13 includes an upper tapered
 section 42 bounded by an outer surface 43 and a rounded surface 44 which
 terminates in a lower edge 45. An inner surface 46 is slightly tapered and
 extends downwardly to the area of the edge 45. A medially positioned
 section 48 is of relatively thin cross section, and is bounded by an outer
 surface 49 and an inner surface 50. A lower section 52 includes an annular
 main body 53 of relatively thicker cross section bounded by an upper
 radially extending surface 54 and an inner cylindrical surface 55 which
 extends to a lower tapered surface 56 which meets a downwardly extending
 bead 57. The surfaces 54 and 55 meet in an area of relatively thin cross
 section indicated by reference character 60, from which extend a plurality
 of hinged tabs 61, conveniently eight in number. The tabs, in unstressed
 condition, extend inwardly at approximately thirty degrees with respect to
 the principal axis of the closure and are generally triangular in cross
 section. Each tab is bounded by an outwardly extending surface 65, an end
 surface 66 which meets the surface 65 in a rounded bead 67. An inner
 surface 68 extends downwardly from the end surface 66 from an edge 69 to
 the area of thin cross section 60 which forms a hinge for the tab which is
 relatively rigid. Extending from the surface 68 are a pair of shaped
 projections 70 bounded by first and second surfaces 71 and 72 and end
 surfaces 73. Referring to FIG. 4 in the drawing, it will be observed that
 these projections are adapted to contact the surface 55 which determines
 the limit of the path of travel which the tabs may execute when the
 container is unthreaded. In this position, the outer surface 65 is
 disposed at approximately 49 degrees with respect to the principal axis of
 the closure, whereas in unstressed condition, the surface is disposed at
 approximately 20 degrees from the principal axis. Thus, the tabs operate
 only in a single mode in which they are in relatively upright condition,
 thus assuring a rapid breaking of the frangible bridges during the initial
 portion of the unthreading operation which removes the closure from the
 container. While pivoting inwardly, a considerable degree of leverage is
 obtained whereby the manually transmitted force exerted by the user to
 unthread the closure is substantially reduced.
 Turning now to FIGS. 4, 5, and 6 in the drawings, there are illustrated
 three alternate constructions, in which, to avoid needless repetition,
 certain of the component parts corresponding to those of the principal
 embodiment have been designated by similar reference characters with the
 additional prefixes "1", "2", and "3".
 In the form illustrated in FIG. 4, the projections 70 have been replaced by
 a single projection 170 to provide slightly greater rigidity to the tab
 when flexed to its inward limit of travel.
 In the form shown in FIG. 5, the annular main body 253 is shortened in
 height, to form a somewhat larger bead 257, thereby saving a degree of
 material from which the device is molded.
 In the form illustrated in FIG. 6, the annular main body 353 is extended
 inwardly beneath the area of thin cross section 360, so that the tab
 contacts the upper radial surface 354 rather than the inner cylindrical
 surface 355 when flexed, this construction being particularly suitable
 where the tamper ring is not split upon removal of the closure.
 The invention will be best understood from a comparison of the disclosed
 structure herein with that disclosed in my prior U.S. Pat. No. 5,107,998
 granted Apr. 28, 1992 under the title "Tamper Proof Ring For Threaded
 Containers".
 In my prior patent, the disclosed tamper-indicating ring includes an
 inwardly directed lower flange which supports a plurality of hook-like
 members, i.e. tabs, against movement past a predetermined point when the
 closure is unthreaded. The base of the tabs is formed to interconnect with
 a curved outer portion of the upper surface of the supporting flange (See
 FIG. 3), so that when the tab is forced downwardly as shown in FIG. 4, an
 inwardly oriented side surface moves against the more inwardly disposed
 upper surface of the flange, at which point further downward movement is
 prevented. This movement develops substantial leverage against the outer
 surface of the container finish, and results in the splitting of the
 tamper indicating ring prior to the breaking of some of the frangible
 bridge members, so that with further unthreading, some of the bridges
 remain unbroken and the split tamper indicating ring remains attached to
 the skirt of the closure. The entire cross section of the tabs is,
 therefore, of relatively thick cross section, so that a compressive force
 is exerted against the relatively thin medially disposed portion of the
 tamper ring to result in splitting the ring in that area.
 By contrast, the presently disclosed structure is directed to the
 separation of the tamper indicating ring from the closure skirt without
 splitting the ring, so that it will remain attached to the container as
 the closure is unthreaded. This is accomplished without the tabs being
 pivoted to a degree wherein they overlie an inwardly disposed generally
 vertical surface of a bead to decrease the effective internal diameter of
 the tamper indicating ring to less than that of the corresponding bead on
 the container finish as described, e.g. in the McBride U.S. Pat. No.
 4,938,370 of Jun. 3, 1990. That structure necessitates a relatively
 flexible or flabby tab which very often is too thin in cross section to
 permit operation in a so-called first mode. As a result, the closure must
 be unthreaded to a considerably greater degree before the frangible
 bridges interconnecting the ring with the skirt of the closure are broken,
 often at the limit of the threaded engagement, and without the obtaining
 of substantial leverage possible only in the first mode of operation.
 The present construction, therefore, is directed to the provision of tabs
 which are of substantial cross section along the length thereof, but which
 have a hinged interconnection at a location of relatively thin cross
 section, so that they will pivot instead of flex relative to the tamper
 indicating ring body as the closure is unthreaded to a relatively limited
 degree, and exert a force against the tamper ring body which is, for the
 most part, axially directed relative to the axis of the closure, and
 results in prompt separation of the tamper ring, substantially at the
 initiation of the unthreading action.
 To accomplish this result, it is necessary that the tab be free to pivot
 outwardly to readily clear the tamper ring bead on the container finish
 when the closure is unthreaded, but be limited in inward pivotal movement
 in an opposite arcuate path of movement to no more than 40 degrees from
 the axis of the closure. This can be accomplished using a variety of
 structures. In the principal embodiment, the triangularly shaped
 projections contact the inner surface of the tamper ring at the lower main
 body thereof to prevent further movement. This is equally true in the case
 of the first and second alternate forms. In the third alternate form
 contact by the tab is made with a radially inwardly extending surface of
 the lower main body to create a similar effect.
 I wish it to be understood that I do not consider the invention to be
 limited to the precise details of structure illustrated and described in
 the specification, for obvious modifications will occur to those skilled
 in the art to which the invention pertains.