Abstract:
The present development is for a closure which provides a liner for abutting a surface and maintaining an effective pressure against a peelable seal affixed to a container lip as the sealed container is exposed to relatively high temperature and pressure conditions. The liner which abuts a surface of the seal sandwiches the seal between the liner and the container lip. The liner defines a resting thickness at ambient temperature and pressure conditions and is made from a material capable of being compressed to a thickness less than the resting thickness and of recovering to a recovery thickness sufficient to allow the liner to maintain a positive pressure against the seal upon exposure to elevated temperatures, elevated pressure, or a combination of elevated temperature and elevated pressure.

Description:
BACKGROUND 
   The present invention relates to a closure for a closure container that has a peelable seal and that is sterilized using a retort process. The closure causes the seal to maintain a positive pressure against a container lip as the container undergoes sterilization by retort processing thereby minimizing the risk of leakage under the seal. 
   In recent years, packaged products which are room temperature storage stable yet ready-to-use upon opening, i.e. they require no cooking or heating before use, have become extremely popular with the consumer. For many food products, this trend requires only minor packaging changes, such as modifying the package size to be consistent with the anticipated consumer use pattern. However, for products prone to bacterial contamination and spoilage, such as milk-based beverages, soups, and many other low acid food products, this trend presents some major packaging challenges. For example, milk-based and low acid food products need to be sterilized to reduce the initial viable bacterial concentration in a product, thereby reducing the rate at which the product will spoil and lengthening the product&#39;s shelf-life. One procedure for reducing the viable bacterial concentration is sterilization by retort processing. In the retort process, a chilled or ambient temperature product is poured into a container and the container is sealed. The container may be sealed by melding two sections of the container material together, such as by heat-sealing a seam on a pouch, or the container may be sealed by bonding a seal to the lip of the container, such as by induction sealing a foil-lined seal to a barrier polymer material bottle neck. The filled package is then sterilized at high temperature in a high pressure water bath. In a typical commercial production rate retort process, the package is heated from an ambient temperature of about 75° F. to a sterilizing temperature in the range of from about 212° F. to about 270° F. As the exterior surface of the package is heated, the package contents are heated and the internal (vapor) pressure increases. By concurrently, submerging the package in the water bath, a counteracting external pressure increase is applied to the container. 
   Although the retort process is an efficient sterilization process, it is harsh on packaging materials because of the temperature and pressure variations involved. Materials commonly used for stand-up, reclosable containers, such as plastic bottles, tend to soften and distort during retort processing. Materials used for seals can soften and, because the seal material is distinct from the container material, can form small gaps or pinholes at the bond interface. These gaps or pinholes can allow product to vent out of the container as the internal pressure increases during the retort process and can allow process bath water to enter the container as the internal pressure decreases relative to the external pressure and the package returns to ambient conditions. Because the packaged beverage and the process water may pass through very small gaps at the bond interface, this event may occur even though the product appears to have an acceptable seal. Moreover, the container and seal may enter the retort process in a less than ideal condition because the process to adhere the seal to the container can cause the neck, the lip, the threads or a combination thereof on the container to distort slightly. If the seal is transferred to the neck with a closure mounted on the container, the skirt, top, threads or a combination thereof on the closure may distort during the seal transfer process. These material failures can increase the number of manufacturing errors and can allow for product contamination even on packages that appear to meet quality standards. 
   Barrier pouches minimize the risk of material failures during retort processing because the pouch usually has sufficient flexibility that it can alter its shape in response to the over-pressure conditions of the retort process. Moreover, barrier pouches generally have minimal headspace within the sealed pouch so the packages are less affected by the external pressure changes than are packages with relative large headspaces, such as semi-rigid bottle-like containers. Further, the seals or bonds are created by melding the pouch material to itself thereby creating strong, non-distinct bonds. Hence, well-sealed packages which are not dependent on maintaining their original shape can be produced. However, the pouches usually require specialized devices, such as sharp-tipped straws, to open the package and do not allow the consumer to reclose the package after opening. 
   For bottles or similar stand-up containers that are sealed such that the seal can withstand the retort process, a different problem may be created. The seal may adhere so tightly to the container lip that when the consumer attempts to remove the seal, the seal may be very difficult to remove from the container, and/or may tear into small pieces and leave fragments along the container rim. If the product is a beverage or similar liquid product, the product may settle under the seal fragments as the beverage is dispensed. This can make the product aesthetically unacceptable and unpleasant for repeated use by the consumer and increase the probability of bacterial contamination under the seal fragments. Further, the user risks being cut or scratched by the remaining foil bits along the container lip. Semi-rigid containers also have relatively large headspaces thereby allowing the user to shake and remix the product immediately before dispensing. However, during retort processing, the air-filled headspace will be affected more rapidly than the liquid product by the temperature changes increasing the pressure against the seal and thereby increasing the probability of seal failure. 
   SUMMARY OF THE INVENTION 
   The present invention is for a closure for a container that has a peelable seal wherein the sealed container is sterilized using a retort process. The closure provides a means for maintaining an effective pressure against the seal to prevent seal separation or leakage as the sealed container is subjected to the temperature and pressure deviations of the retort process. 
   Specifically, the closure includes a resilient liner and a skirt with at least one thread affixed to the skirt interior surface. The liner fits firmly within the closure, defines a resting thickness “t” at ambient temperature and pressure conditions, and is made from a material capable of being compressed to a thickness less than the resting thickness “t” and of recovering to a thickness sufficient to maintain an effective pressure between the closure and the peelable seal affixed to the container. In an embodiment of the present invention, the liner is made from a material capable of being compressed to a thickness less than the resting thickness “t” and of recovering to a thickness not greater than the resting thickness “t”. In an alternative embodiment of the present invention, the liner is made from a material capable of being compressed to a thickness less than the resting thickness “t” and of recovering to a thickness which may be greater than the resting thickness “t”. Also, in an embodiment of the present invention, the thread defines an angle θ between the upper edge and a horizontal plane and the angle θ is less than about 45°. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a sectional view of a closure made in accordance with the present invention; 
       FIG. 2  is a sectional view of a container with a seal amenable for use with the closure of  FIG. 1 ; 
       FIG. 3  is a top view of the container of  FIG. 2  with a seal on top; 
       FIG. 4  is a sectional view of the closure of  FIG. 1  shown with the container of  FIG. 2  in a normal fully inserted position; 
       FIG. 5  is a sectional view of an alternative embodiment of a closure made in accordance with the present invention having a plurality of folding fingers as the engaging means for the tamper-evident band; 
       FIG. 6  is a side view of the closure of  FIG. 5 ; 
       FIG. 7  is a sectional view of a second alternative embodiment of a closure made in accordance with the present invention and having a continuous band as the engaging means for the tamper-evident band; 
       FIG. 7A  is a cut-away view of the closure of  FIG. 7  showing the segmented bottle bead; 
       FIG. 8  is a side view of the closure of  FIG. 5  having a slotted skirt; and 
       FIG. 9  is a sectional view of the closure of  FIG. 1  shown with a seal affixed to the liner. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention is for a closure for a container that has a peelable seal wherein the sealed container is sterilized using a retort process. The closure provides a means for maintaining an effective pressure against the seal to prevent seal separation or leakage as the sealed container is subjected to the temperature and pressure deviations of the retort process. The closure and container depicted in the various Figures is selected solely for the purpose of illustrating the invention. Other and different closures, containers, or combinations thereof, may utilize the inventive features described herein as well. 
   Reference is first made to  FIGS. 1-4  in which a closure constructed in accordance with the present invention is generally noted by the character numeral  10 . The closure  10  includes a cap  20  and a liner  40 . As generally shown in  FIG. 1 , the cap  20  includes a top  22 , a skirt  24  depending from the top  22 , and at least one thread  26 . The top  22  and skirt  24  have interior surfaces  23  and  25 , respectively. The thread  26  is affixed to the interior surface  25  of the skirt  24 , circumscribing the skirt  24  in a spiral such that a depression or thread receiving groove  27  is formed. The thread  26  defines an upper edge  28 , a lower edge  30  and a face  32 . As is known in the art, the upper edge  28  and lower edge  30  are angled from a horizontal plane “X” causing the thread  26  to have beveled edges rather than sharp corners at the face  32 , and allowing the thread  26  to be optimized for strength, cooling and material usage. In the closure  10  of the present invention, the angle for the upper edge  28  is preferably relatively close to horizontal. For example, an angle θ defined between the horizontal plane X and the upper edge  28  is not greater than about 45°, and preferably is less than about 20°. In the embodiment shown, the angle θ is about 10°. 
   The liner  40  abuts the top interior surface  23  of the cap  20  and is sized to fit firmly within the cap  20 , i.e., the diameter of the liner  40  is large enough that the liner  40  can be held within the cap  20  by the thread  26  without the need for a bonding material. Optionally, as shown in  FIGS. 1 and 4 , the liner  40  may be adhered to the top surface  23  by a variety of means known in the art, such as with a thin layer of adhesive, thermoplastic polymeric material, glue or similar bonding material  48 . Combinations of bonding material layers may be used as desired by the user. The liner  40  defines a resting thickness, “t”, which is the unrestrained thickness of the liner  40  at ambient temperature and pressure conditions. The material selected for the liner  40  should be sufficiently pliable or elastic that the liner  40  can be compressed between the cap  20  and a container  60 , thereby decreasing the liner thickness “t”. But, the liner  40  material should also be sufficiently resilient that the material can recover from the compressed state to define a recovery thickness, “t r ”, at ambient temperature and pressure conditions or under stress temperature and pressure conditions, such as are present during a retort process. The recovered thickness of the liner  40 , t r , may be essentially equal to, less than, or greater than the resting thickness, t. The recovery thickness, t r , should be sufficient to allow the liner  40  to maintain a positive pressure against the cap  20  and a seal  80  affixed to a container lip  68 , wherein the pressure is adequate to prevent the seal  80  from separating from the container  60 . To maintain the pressure against the seal  80 , the liner  40  should have sufficient elasticity that it can conform to any distortions in the container lip  68 , such as molding nubs or small divots or voids. For example, the liner  40  may be made from a thermoplastic or a thermoset material such as a silicone-based material, urethane, latex, rubber, a thermoplastic elastomeric material such as Santoprene®, or a combination thereof. Optionally, the liner  40  may be made from a material having a melting point greater than the anticipated maximum retort processing temperature, such as about 265° F., and having a shore A value of about 70. To enhance the expansion capabilities of the material, the liner  40  material may also include foaming agents, entrapped or encapsulated gases or similar expanding agents. Because the liner  40  is in direct contact with the seal  80 , the materials selected for the liner  40  should not bond to the seal  80 . 
   The closure  10  is designed to function cooperatively with the container  60  having the removable seal  80 . As shown in  FIGS. 2-4 , the container  60  has a neck  62  which extends vertically from shoulders  64  and terminates in an opening  66 , defining the lip  68  having a periphery  69 . As shown in  FIGS. 2 and 3 , the neck  62  has an exterior face  63  adapted to allow the container  60  to receive and engage the cap  20 . The engaging face  63  includes a container thread  70  fixedly attached to the engaging face  63 , and a thread receiving groove  72 . The thread  70  may have one of a variety of thread configurations, such as a single helix (1 strand), a double helix (2 strands), a triple helix (3 strands) or other multiple helices, as are known in the art. Optionally, the neck  62  may include a bottle bead or collar  74 . The bottle bead  74  is an annular projection located near the shoulder portion  64  of the container  60  and encircling the neck  62 . The container  60  may be manufactured from a variety of materials as are known in the art for container use. Preferably, the container  60  is made of a rigid or semi-rigid polymeric material which can withstand retort processing conditions. 
   The seal  80  has a top face  82  and a container face  84 . The seal  80  is reversibly affixed to the container lip  68 , and preferably, is affixed to the lip  68  such that the seal  80  can be completely removed from the lip  68  by the user without tearing, shredding or leaving consumer noticeable fragments on the container lip  68 . As is known in the art, the seal  80  may be proportioned to match the periphery  69  of the container neck  62 , or it may be proportioned to extend beyond the periphery  69  thereby partially covering the exterior face of the neck  62 , or it may be proportioned to match the periphery  69  in some sections and to extend beyond the periphery  69  at other sections, such as by including one or more tabs  86 . The seal  80  preferably has sufficient strength and elasticity to allow the seal  80  to conform to the container lip  68  while accommodating any distortions, such as molding nubs or small voids or divots, and to expand and contract in the retort process without rupturing. Further, the seal  80  preferably can be adhered to the container lip  68  to form a semi-permanent bond between the seal  80  and container  60 . 
   In the embodiment shown in  FIGS. 1 and 4 , the closure  10  is reversibly attached to the container  60  after the container  60  is filled and has the seal  80  affixed to the container lip  68 . The container contents are then sterilized with retort processing. In a typical process, the filled package is transported through a high pressure overheated water bath, wherein the package is heated to from about 75° F. to about 265° F. for a predetermined period of time. As the exterior surface of the package is heated, the package contents are heated and the internal (vapor) pressure increases. Concurrently, the package is submerged to greater depths in the water bath resulting in a counteracting external pressure increase. The package is then slowly raised—moved to a more shallow depth—as the package is concurrently transported into a cooler zone in the water bath. The rate of movement into the cooler zone and shallower depth is designed to minimize variations in the internal pressure of the package. After a predetermined time, the package is removed from the water bath and allowed to cool to room temperature. 
   As shown in  FIG. 4 , the closure  10  functions cooperatively with the container  60  and seal  80  to provide an added measure of protection for the seal integrity as the container contents are sterilized by the retort process. Specifically, the closure  10  fits over the container neck  62  and the cap thread  26  complements the container thread  70  with the cap thread  26  fitting within the container receiving groove  72  and the container thread  70  fitting within the cap receiving groove  27 . Further, the cap  20  and the liner  40  are proportioned such that when the container  60  is fully inserted in the closure  10 , a bottom face  42  of the liner abuts the seal  80 . In the embodiment shown in the Figures, the cap thread  26  and the container thread  70  are single helices, but any complementary thread design may be used provided the thread design can withstand the processing conditions. 
   During the retort process, the liner  40  functions cooperatively with the cap  20  to provide a pressure against the seal  80  opposing the container lip  68 . Specifically, when the closure  10  is attached to the sealed container  60  at ambient temperature and pressure conditions, the cap  20  may be tightened on the container  60  such that the liner  40  is compressed slightly between the container lip  68  and the top interior surface  23  of the cap  20 . A sealing zone  46 , shown in  FIG. 4 , is thereby formed where the seal  80  and liner  40  are sandwiched between the cap  20  and the container lip  68 . When the closure  10  and sealed container  60  are exposed to the retort conditions, the seal integrity is challenged by pressure increases within the container  60 . With the liner  40  pressing the seal  80  against the container lip  68 , the probability of the seal  80  separating from the container lip  68  as the pressure changes within the container  60  is minimized. Further, when the closure  10  and sealed container  60  are exposed to the high pressure retort conditions, small droplets of water from steam or the water bath may attempt to migrate into any void spaces that are present between the container  60  and the closure  10  because of the increased pressure outside the container  60 . By forming a tight barrier between the top interior surface  23  of the cap  20  and the top face  82  of the seal, the liner  40  can minimize the risk of water droplets migrating between the cap  20  and the seal  80 . 
   During the retort process, the angle θ of the cap and closure threads  26 ,  70  functions to hold the closure  10  on the container  60 . Because of the pressure changes in the container associated with the retort process, the container may be distorted, and the distortion can affect the interaction of the container threads  70  with the cap threads  26 . Threads with an essentially horizontal angle θ are stronger than threads having a larger angle θ. As the thread strength increases, the probability of the threads stripping and loosening decreases. Thus, because the threads of the closure  10  have a relatively small angle θ, the closure  10  is held securely on the container  60  and the liner  40  is held against the seal  80 . 
   The closure  10  may remain on the container  60  until removed by the consumer. Optionally, the closure  10  may be removed from the container  60 , the exterior surface of the neck  63  may be dried, for example with heated air, and a commercial closure may be applied. The commercial closure may be essentially identical to the closure  10 , it may include tamper-evident features, or it may include other consumer-desired or aesthetic features, as are known in the art. However, small droplets of water can migrate under pressure from the water-bath into any void spaces that are present between the container  60  and the closure  10  during the retort process. Thus, if the closure  10  is to remain on the container  60  after processing, the closure  10  is preferably adapted to allow water to drain from spaces between the closure  10  and the container  60 . 
   As shown in  FIGS. 5 and 6 , an alternative embodiment of the closure  110  is intended to be attached to the container  60  before retort processing and to remain on the container  60  until removed by the consumer. The closure  110  is essentially identical to the closure  10  except that a skirt  124 , depending from a top  122 , terminates with an essentially circular tamper-evident band  134 . The tamper-evident band  134  can be similar to any known tamper-evident or child-resistant band provided the band includes some void areas which would allow water droplets to drain from the band. In the embodiment shown, the tamper-evident band  134  includes a break-away section  136  and a means  138 , such as flexible finger projections, for positively engaging the collar  74 . As is known in the art, the flexible finger projections include spaces between the fingers which allow any trapped water to drain from the band  134 . In addition, some water drainage may be provided through apertures  137  in the break-away section  136 . 
   A second alternative embodiment  210  of a closure with a tamper-evident band  234  is shown in  FIGS. 7 and 7A . The closure  210  is similar to the closure  110  of  FIG. 5  except that the means for positively engaging the collar  74  is a bead  238  encircling the skirt  224 . The bead  238  has an internal diameter slightly greater than the external diameter of the exterior surface of the container neck  63  so that a gap  275  remains between the bead  238  and the neck exterior surface  63 . Additionally, optional gaps or breaks  274  are preferably included in the container collar  74  to allow water droplets to drain from band  234  and to improve the air circulation between the skirt  224 , band  234  and the container neck  62 . 
     FIG. 8  shows a third alternative embodiment of the closure  310  which allows for air circulation between the container neck  62  and the cap skirt  324 . The closure  310  of  FIG. 8  is identical to the closure  110  of  FIG. 5  except that ventilation slits  335  have been added to the cap  320  running a predetermined length from the top  322  to the skirt  324 . The slits  335  may extend a slight distance onto the top  322  but may not breach the sealing zone  46 . The slits  335  allow air to circulate between the container neck  62  and the skirt  324 . The number and precise positioning of the slits can vary as necessary for the particular container/closure combination. 
   As described in the embodiments of  FIGS. 1-8 , the seal  80  is secured to the container lip  68  before the closure  10  is affixed to the container  60 . However, as shown in  FIG. 9 , the seal  80  may be delivered to the container  60  via the closure  10 . For example, the seal  80  may be included as a transferable part of the liner  40 , wherein the seal  80  is reversibly secured to a bottom face  44  of the liner  40 . Using the embodiment of  FIG. 9 , the closure  10  may be reversibly attached to the container  60  such that the seal  80  abuts the container lip  68 . The seal  80  can then be secured to the container lip  68  and released from the liner  40  using known heat-sealing techniques, such as induction heat sealing or conduction heat sealing. After the seal  80  has been affixed to the container lip  68 , the closure  10  can be removed from the container  60  with the liner  40  remaining in the closure cap  20  and the seal  80  remaining on the container  60 . The seal  80  is preferably transferred from the liner  40  to the container lip  68  before the container  60  is subjected to the retort processing conditions. The retort process then proceeds as described for the embodiment shown in  FIGS. 1-4 . 
   From a reading of the above, one with ordinary skill in the art should be able to devise variations to the inventive features described herein. These and other variations are believed to fall within the spirit and scope of the attached claims.