Abstract:
The invention is a twist-off closure cap and container assembly that provides the advantages of a tamper-indicating pilfer band with the attractive appearance of a metal crown cap. The closure cap is an overlay having a bright, metallic sheen and the coloration of brass or burnished steel. A printed design or logo reminiscent of a crown metal beer of soft drink cap may be printed on the overlay. The container is provided with an annular bulge that complements the pilfer ring of the closure cap. The closure cap also includes corrugated depressions, internal helical grooves and frangible bridging elements for detachably connecting the closure cap with the pilfer band. The pilfer band includes an interference lip that engages with a locking ring on the container so that when the closure cap is rotated with respect to the container the pilfer band stays with the container.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to tamper-indicating closures for containers and more particularly to a blow molding preform and a tamper-indicating plastic closure cap including a laminated film overlay.  
         BACKGROUND OF THE INVENTION  
         [0002]    Crown caps are widely utilized for sealing glass bottle openings. These caps are typically formed of sheet metal and include a top, a side wall and a flared skirt. The skirt has a plurality of flutes that extend around the circumference at spaced intervals. When pressed onto an open end of a glass bottle having a bead about the opening, these flutes bend at the points of intersection between the bottle and the skirt, gripping the bead to seal the bottle. The circular, central top of the cap usually has a resilient lining on its internal surface composed of, for example, cork or a polyethylene derivative, which is placed against the end of the bottle to create a hermetic seal.  
           [0003]    The crown cap has been used for some time to seal glass bottles, particularly for storing beverages bottled under pressure such as beer or carbonated soft drinks. Consumers generally associate the crown cap with containers for traditional, high-quality beverages. However, the crown cap is to difficult to open without the use of a bottle opener and practically impossible to reseal.  
           [0004]    Previously disclosed twist-off, tamper-indicating closures include an upper closure cap having a skirt and an annular pilfer band depending from the skirt portion. The pilfer band is partially or completely detachably connected to the skirt portion by a series of circumferentially-spaced, frangible bridges or a scored sheet. The annular band portion typically remains on the neck of the container after it has been detached from the skirt portion.  
           [0005]    One type of twist-off tamper-indicating closure is composed of a polymer material, such as high-density polyethylene (“HDPE”), and includes an interference-type pilfer band detachably secured to the closure by a frangible member. Containers for use with these interference-type pilfer bands have annular external locking rings on their neck portions, positioned beneath external screw threads on the outside of the container neck. The pilfer band includes a ledge for engaging the container locking ring. Specifically, the ledge is configured to move past the container locking ring when the closure is screwed onto the container to interferingly engage the container locking ring. When the closure is twisted off of the container, the frangible member breaks and the pilfer band remains on the container.  
           [0006]    Traditional twist-off tamper-indicating closures are not entirely satisfactory because they do not normally accept and retain intricate printing. This is probably because interference-type pilfer bands and the closures that include them are usually composed of HDPE and polyethylene terephthalate (“PET”). Consequently, applying attractive decorative designs and logos to the exterior surface of the tamper-indicating closure is problematical.  
           [0007]    The plastic bottling industry expands partially formed containers, known as “preforms,” in a stretch blow molding process to fabricate containers having threaded necks for mating with screw tops. The blow molding process permits high production rates and is capable of forming containers having narrow necks and voluminous bodies. However, the blow molding process, by itself, cannot produce screw threaded necks, which are better suited to fabrication by injection molding. While some hybrid processes are currently practiced, such as injection blow molding, the hybrid processes are not completely satisfactory because, among other things, they are much slower that traditional blow molding processes. Consequently, manufacturers typically produce or purchase quantities of injection-molded preforms that include screw-threaded tops, and then heat and expand the preforms to produce finished bottles by the stretch blow molding process.  
           [0008]    The construction material for the preforms, which is the same as the finished plastic bottles, is usually dictated by the chemical composition of the liquid contents to be stored in the bottles and the temperature at which the bottles are to be filled. PET is an excellent material for stretch blow molding and is commonly used for carbonated beverage bottles. Related compositions, such as PETE, can also be used successfully. PET provides very good alcohol resistance and generally good chemical resistance. PET can be injection molded to produce preforms for stretch blow molding. PET is generally not suitable as a closure cap for carbonated beverages, which can generate significant internal pressure.  
           [0009]    Polyvinyl chloride (“PVC”) and polycarbonate are acceptable construction materials for closure caps, with PVC being preferred. PVC is relatively strong without being objectionably brittle and is easily injection molded. PVC is also a good substrate for fine printing. However, the shapes of beverage closure caps make it difficult to print on the closure caps after they have been injection molded.  
           [0010]    Another long-standing problem is that previously disclosed tamper-indicating closures simply do not look like metal crown closures. For whatever reason, consumers prefer crown closures for certain beverages, such as beer and carbonated soft drinks, and have consistently resisted the introduction of flexible plastic bottles and tamper-indicating closures for these beverages.  
           [0011]    A need exists for a tamper-indicating closure equipped with an interference-type pilfer band that resembles a metal crown cap when installed on a flexible plastic beverage container. The new closure should be resealable and removable by hand or by bottle opener. Desirably, the new closure should twist off without exposing any sharp edges and should accept attractively printed designs and logos as are commonly seen on metal crown caps. Ideally, the new closure should fit a container having a shape that complements and disguises the silhouette of the interference-type pilfer band.  
         SUMMARY OF THE INVENTION  
         [0012]    The invention is a twist-off closure cap that presents the appearance of a metal crown cap and includes an interference-type pilfer band. The closure cap includes an overlay that exhibits the metallic shine and color of brass or steel. The overlay surrounds the upper portion of the twist-off closure and, if properly prepared, can be printed with attractive logos and designs as are commonly seen on metal crown caps. The invention also provides a container that receives and complements the pilfer band.  
           [0013]    The closure cap includes a generally cylindrical side wall and a flared skirt having a fluted outer surface and an inner surface having generally helical grooves. The pilfer band depends from the skirt portion and includes an inner surface that forms an interference lip. Frangible elements connect the pilfer band to the skirt portion.  
           [0014]    The overlay is preferably dyed to resemble a bright, metallic bronze or steel finish. Portions of the overlay may be printed with fine artwork comparable to that seen on conventional crown caps for beer and carbonated beverage containers. The overlay is a laminated film structure that is bonded to the cap during an injection molding process.  
           [0015]    The container includes a neck forming a dispensing opening and a neck surface surrounding the dispensing opening. A generally helical ridge extends from the neck surface and cooperates with the generally helical grooves of the closure cap so that the closure cap is raised with respect to the container when the closure cap is rotated in a counterclockwise direction. When properly installed, the interference lip of the pilfer band is engaged with a locking ring that extends from the container and, as a result, cannot rise when the twist-off cap is rotated. Consequently, rotating the closure cap in a counterclockwise direction breaks the frangible bridging elements, leaving the pilfer ring attached to the container. The container includes an annular bulge situated adjacent the locking rings, which blends with the silhouette of the pilfer band. Particularly when the container and the pilfer band are the same color, the pilfer band is inconspicuous. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is an elevation view of an assembly including a twist-off closure cap and an associated container;  
         [0017]    [0017]FIG. 2 is an elevation view of the closure cap depicted in FIG. 1;  
         [0018]    [0018]FIG. 3 is a cross-sectional view of the closure cap depicted in FIG. 1;  
         [0019]    [0019]FIG. 4 is a partial cross-sectional view of the overlay depicted in FIG. 3; and  
         [0020]    [0020]FIG. 5 is a cross-sectional view of a mold used in an injection molding process to produce the closure cap depicted in FIG. 1. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]    In a preferred embodiment, the invention is twist-off closure cap and complementary container assembly  1  as depicted in FIG. 1. Assembly  1  includes container  50 , which is a blow-molded polyethylene terephthalate (“PET”) preform specifically adapted for use with closure cap  10 . As shown in FIG. 1, container  50  includes neck  52  surrounding dispensing opening  54  through which liquid contents may be filled and emptied. Neck  52  is surrounded by neck surface  56 , generally helical ridges  58  and locking ring  60 , which extends generally radially from neck surface  56 . Ridges  58  cause closure cap  10  to rise or fall with respect to neck  52  when closure cap  10  is rotated on the end of neck  52  counterclockwise or clockwise, respectively. Locking ring  60  engages interference lip  30  (best seen in FIG. 3) of closure cap  10  so as to prevent interference lip  30  from rising when closure cap  10  is rotated counterclockwise. Annular bulge  62  is disposed about container  50  adjacent locking ring  60 . Bulge  62  has a profile or silhouette that blends with and complements the silhouette of closure cap  10 .  
         [0022]    Container  50  is preferably composed of PET, which is widely used for flexible liquid storage containers. Container  50  may be clear or colored. Clear PET is popular for water containers. Green or amber PET resembles the type of glass commonly used for beer bottles. For storing carbonated beverages, the walls of container  50  are made relatively thicker than those of flexible plastic storage containers used for water and the like. For storing carbonated beverages, container  50  has a mass of 28 grams, as compared to a generally accepted 22 grams of mass for a standard flexible container.  
         [0023]    Turning now to FIG. 2, closure  10  includes substrate  11  (best seen in FIG. 3), which is substantially covered by overlay  13 . Generally circular skirt portion  14  surrounds circular top wall portion  12  and includes outer surface  25 , which is crimped or corrugated to produce flutes. Each flute includes a substantially trapezoidally-shaped trough or depression  26  between a pair of crests  27 .  
         [0024]    Closure cap  10  also includes fracturable bridging elements  20 , which are shown in FIG. 2. Each of the bridging elements  20  is a vertically-oriented sliver of material calculated to fracture when closure cap  10  is moved away from container  50 . Alternatively, closure cap  10  may include a sheet having a plurality of scored sections (not shown) that are calculated to fracture upon movement of closure cap  10  away from container  50 . Inside surface  24  includes generally helical grooves  28 , which cooperate with ridges  28  to move closure cap  10  toward or away from container  50  when closure cap  10  is rotated.  
         [0025]    As depicted in FIG. 2, bridging elements  20  detachably connect closure cap  10  to pilfer band  16 , which is generally in the shape of a band surrounding bore  32 . Neck surface  56  (best seen in FIG. 1) is sized to fit within bore  32 . Pilfer band  16  includes interference lip  30  equipped with undercut  31  for engaging locking ring  60  when closure cap  10  is installed on container  50 . In practice, this is accomplished by sliding bore  32  over the neck surface  56  until ridges  58  contact grooves  28  (best seen in FIG. 3) and then rotating closure cap  10  clockwise with respect to container  50  until locking ring  60  slips past interference lip  30  and engages undercut  31 .  
         [0026]    [0026]FIG. 3 is a cross-sectional view taken along plane X-X in FIG. 2 depicting the manner in which bridging elements  20  are formed on inside surface  24 . Grooves  28  can be seen on inside surface  24 .  
         [0027]    Overlay  13 , depicted in partial cross section in FIG. 4, is a laminated film structure that is bonded to substrate  11  (best seen in FIG. 3). Overlay  13  includes sealing film  40 , which is preferably composed of the same material as substrate  11 . Sealing film  40  may be composed of, for example, PVC or a polycarbonate. Laminated film structures suitable for use in the invention are commercially available from Multi-Color Corp. of Cincinnati, Ohio, or Label Tek of Yorkville, Ill., for example. In the depicted embodiments, sealing film  40  partially melts under controlled conditions so that it becomes welded at one surface to substrate  11 . While melting or thermal welding is preferred, the invention may be successfully practiced by attaching sealing film  40  to substrate  11  by, for example, solvent welding, ultrasonic welding or applying a heat-setting adhesive.  
         [0028]    In contrast, surface  42  does not melt or become significantly distorted while surface  41  is attached to substrate  11 . Preferably, surface  42  has been previously attached to surface  43  of printed film  44  by thermal welding, ultrasonic welding, solvent welding, adhesion or some similar process and provides stable support for printed film  44 . Varnish film  47 , which protects against thermal shock and mechanical abrasion, is located on printing surface  45 .  
         [0029]    Film  44  may be dyed or printed to resemble a bright, metallic surface (such as bronze or steel), a painted surface or a printed surface. Preferably, as shown in FIG. 2, portion A is printed to resemble a painted metal crown cap and portion B is dyed or printed to resemble an unfinished edge of a metal crown cap. Portion C is preferably clear or the same color as a container intended for mating with closure cap  10 .  
         [0030]    The invention is also a process for manufacturing closure cap  10  and container  50 . A vacuum pick-up tube (not shown) is used to pick up overlay  13  and place overlay  13  in the cavity of mold  80 , which is depicted in closed position in FIG. 5. Although only one mold  80  is depicted, it should be understood that a number of such molds may be operated simultaneously. Vacuum conduits  86  hold overlay  13  in position against upper piece  81  while mold  80  is closed by moving lower piece  83  and center piece  85  toward upper piece  81 , and moving side pieces  82 ,  84  inwardly toward each other.  
         [0031]    Mold  80  is heated using conventional methods. However, a coolant stream flows into inlet port  88  through a channel (not shown) within upper piece  81  and exits through outlet port  89 . The coolant stream cools upper piece  81  and printed film  44  so that printing surface  45  is protected from the full operating temperature of the cavity of mold  80 . Other coolant streams (not shown) may be used to cool the other mold pieces  82 - 85  so as to promote cooling in cavity  92  in order to speed the molding process  
         [0032]    With mold  80  in closed position, hot runner  87  is inserted through conduit  90  in lower piece  83  and through conduit  91  through center piece  85 . Molten PVC is injected into the cavity of mold  80  under a pressure in the range of about 160,000 to about 240,000 pounds per square inch at a precisely controlled temperature in the range of about 180 to about 200 degrees F., which temperature causes sealing film  40  of overlay  13  to bond to attaching surface  42 . When the molten PVC in the cavity of mold  80  sets, which typically occurs in about 2 to about 3 seconds, welding surface  41  bonds to attaching surface  42  of overlay  13 . However, because printing surface  45  is protected from this temperature by the coolant stream, it remains at a temperature below the operating temperature of the mold cavity. Printed matter at printing surface  45  survives the injection molding process and emerges from mold  80  intact and without significant deformation. Exposed dyed material at printing surface  45  emerges from mold  80  with a bright, metallic sheen.  
         [0033]    Upper mold part  81  is retracted generally vertically after closure cap  10  has cooled sufficiently to retain its shape. Left and right mold parts  82 ,  84  are retracted laterally. Lower mold part  83  is retracted downwardly. Finally, closure cap  10  is ejected from core mold part  85 . Although undercuts associated with bridging elements  18  hinder the release of closure cap  10  from core mold part  85 , PVC is sufficiently resilient to permit closure cap  10  to deform during ejection and return to the shape of mold  80 . Closure cap  10  is cooled to room temperature and stored until needed.  
         [0034]    The finished container is produced by subjecting preform container  50  to conventional blow molding processes. Subsequently, the finished container is filled with an appropriate beverage, such as beer or a carbonated soft drink, and closure cap  10  is pressed onto the finished container in a conventional rotary press causing ridges  58  to meet grooves  28 . Closure cap  10  is then rotated clockwise with respect to the finished container in order to advance interference lip  31  over locking ring  60  and engage interference lip  30  with undercut  31 .  
         [0035]    The invention provides an improved closure cap for flexible plastic containers that resembles the traditional metal crown cap found on beer bottles and provides the added advantage of a tamper-indicating interference-type pilfer band. The closure cap can be removed by hand or by bottle opener and, in either case, is resealable. The container of the present invention receives the closure cap and provides a matching silhouette for the pilfer band. The pilfer band and the mating container present the appearance of being a single unit.  
         [0036]    Although descriptions of preferred embodiments and specific examples are provided above in order to better communicate the invention, the invention is not limited by these descriptions or examples. To the contrary, the scope of the invention is defined by the appended claims.