Abstract:
A container finish comprising a helical load carrying member which transmits downward force from the top wall of a closure to the threads of a container to prevent seal failure under stacking load conditions. The helical load carrying member is preferably located on a container neck, parallel to a primary thread. In the alternative the helical load carrying member may be located on a closure finish.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates generally to a top load seal protection feature. More particularly, the present invention relates to a load bearing thread which transmits stacking load from the top wall of a closure to the threads of a container in order to prevent seal failure under stacking load conditions. 
     2. Description of the Related Art 
     When manufacturers mass-produce containers and closures containing food, drink, and the like, the containers are usually shipped to distributors and vendors for public consumption. In order to prepare the containers for shipping, the containers are often stacked in a vertical manner and placed in boxes or crates in a space saving configuration. Throughout shipping and storage of the containers, they remain in this vertical configuration for various periods of time. The extended storage times often result in large vertical loads being placed on the container closures, which may not be factored into their design. As a result of the stacking, large loads may cause sealing gaskets located within the closures to rupture in turn causing leakage, spoilage, or destruction of the food product. 
     Current container closure designs generally suffer from an array of disadvantages, such as those described above, which detract from their efficiency and use. For example, U.S. Pat. No. 4,512,493 to Von Holdt discloses a molded bucket having high stack strength. This design suffers from at least two disadvantages. First, a sealing gasket located preferably on the lid at shelf to seal contents of a bucket would be exposed to the vertical loading attributable to bucket and any other vertically stacked buckets. This design would likely cause a gasket to rupture. Second, this design forces a user to push a closure (lid) onto a container (bucket) therefore eliminating its use as a screw-type closure. 
     Various inventions use a container with a single thread and a small pitch to bear a stacking load. However there are various disadvantages inherent with these structures. First, a container or closure having a small pitch necessarily has a small target area for engagably starting the closure threads on the container threads. Second, machines used for installation of screw on closures often turn closures at a rate of about 500 RPM. This speed in combination with a small target area can lead to manufacturing difficulties and stripped threads. Third, a process comprising pushing a closure onto a container, instead of screwing on a closure may lead to problems like stripped threads and uncertainty as to the orientation of closure threads relative to container threads. 
     In view of the deficiencies in the known container threads and closures it is apparent that a container is needed having top load seal protection characteristics as well as having a closure which is easy to install. It is also preferable that the closure be both closable and openable with a single turn. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a top load seal protection feature. 
     It is a further objective of this invention to provide a load bearing thread operably engaged with a container thread to divert a top load to a container. 
     It is still a further objective of this invention to divert a top load to a load bearing thread of a container and away from a sealing gasket located in a closure crown. 
     It is still an even further objective of the present invention to have the above stated characteristics and yet have a closure which is operable with a single rotation. 
     It is an even further objective of this invention to force the closure to move immediately upward when the cap is unscrewed and prevent cocking such that the closure and bottle maintain axial alignment in spite of the large clearance between threads. 
     More particularly, the present invention provides a container finish comprising an upstanding neck portion, a primary thread helically extending around the upstanding neck portion, a load bearing thread spaced below the primary thread and helically extending around the upstanding neck portion. The load bearing thread preferably starts at a point below a starting point for the primary thread and the load bearing thread is connected to the primary thread by a connecting thread portion. The connecting thread portion is preferably a horizontal thread portion extending from the primary thread. The geometry of the threads is such that the vertical distance in the target area for starting the closure is about twice the vertical distance between the primary thread and the load bearing thread. 
     In an alternative embodiment, the present invention provides a closure finish, comprising a top wall and a skirt depending therefrom, the skirt having a closure thread and a load bearing thread in a spaced helical relationship on an interior surface of the skirt, where the load bearing thread has a starting point or transition area above or below the closure thread at some location along the skirt and may connect to the closure thread by a connecting portion. The vertical distance in the target area of the closure threads is preferably about twice a vertical distance between said closure thread and said load bearing thread. 
     In yet another alternative embodiment the load bearing closure comprises a top wall having an annular skirt depending therefrom, a helically circumscribing thread along an inner surface of the skirt, at least one load bearing protuberance equidistantly spaced and integral with an inner surface of the annular skirt, and each of the at least one of the load bearing protuberances and the helically circumscribing thread forming a groove therebetween for operably receiving a container thread. There are preferably three load bearing protuberances which are preferably spaced about 120 degrees apart. 
    
    
     All of the above outlined objectives are to be understood as exemplary only and many more objectives of the invention may be gleaned from the disclosure herein. Therefore, no limiting interpretation of the objectives noted is to be understood without further reading of the entire specification and drawings included herewith. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The aspects and advantages of the present invention will be better understood when the detailed description of the preferred embodiment is taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a preferred top load seal protection feature of the present invention; 
     FIG. 2 is a sectional view of a preferred top load seal protection of the present invention; 
     FIG. 3 is a sectional view of an alternative embodiment of the top load seal protection feature of the present invention; 
     FIG. 4 is a lower perspective view of an alternative embodiment of the present invention having a continuous load bearing thread; 
     FIG. 5 is a lower perspective view of an alternative embodiment of the present invention having a load bearing thread on top of a primary thread; 
     FIG. 6 is a lower perspective view of an alternative embodiment of the present invention having a load bearing thread below the primary thread and, 
     FIG. 7 is a lower perspective view of a closure of the present invention having a plurality of load bearing protuberances which transfer a stacking load from a closure to a container. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described in conjunction with the drawings, referring initially to FIGS. 1 and 2, which show a top load seal protection feature of the present invention. Generally indicated as reference  10 , the present invention comprises threads formed on a container or closure which remove downward force from the top gasket or seal and transfer it to the container. The closure and container using the designs of the present invention can be made of various materials such as plastics including polyethylene, polypropylene, metal and glass combinations, or other materials, alone or in combination. 
     Closure  11  of FIG. 2 may be preferably injection molded but can be formed by various methods and has an overall cup like shape. Most preferably the closure top wall  12  has a generally circular shape. Depending from the top wall  12  is a skirt  14 . The outer surface of the skirt  14  may be knurled or have vertical ridges for aid in gripping and applying torque to the closure  11 . Circumscribing the inner surface of the skirt are helical closure threads  18 . The closure threads  18  are for operably engaging primary thread  16  located on the container  13  and allow multiple openings and closings of the container  13  after its initial opening. 
     Located within an inner side of closure top wall  12  may be a gasket  20  for sealing the contents of the container  13 . The gasket  20  is preferably made of soft plastic, rubber-like or foam material which forms to the upper lip  19  of container  13 . The gasket  20  seals contents from escaping between the container  13  and the closure  11 . In addition the gasket  20  may prevent air and other contaminants from entering the container  13  which may cause the contents to spoil. 
     During shipping and storage of the containers  13  multiple containers are often stacked in a vertical configuration. A typical result of this stacking is that the gasket  20  is ruptured or otherwise damaged by the upper lip  19  of the container  13  due the top load. However, the present invention overcomes that problem through the use of a load bearing thread  17 . 
     The load bearing thread  17  preferably starts from some point along a primary or container thread  16  so that a user can place the closure  11  on the container  13 , rotate the closure  11 , and easily “start” the closure on the container even though a second thread is provided. Near the top of the container  13 , only a primary thread  16  is needed having a large target area, “T 1 ”, to easily start the closure  11  onto container  13  in between the consecutive helical rotations of the primary thread  16 . The load bearing thread  17  starts as a connecting thread or a horizontal thread portion  21  from the primary thread  16  and may have the same pitch as the primary thread  16 . The load bearing thread  17  runs parallel and below the primary thread  16  as it extends around the container neck  13 . As also shown in FIG. 2, the load bearing thread  17  and parallel primary thread  16  receive closure thread  18  therebetween. Without the load bearing thread  17 , one can see that thread  18  could move downward if a downward force is placed on the closure  11 . However, with the arrangement of the present embodiment the isolation of the closure thread sections  18  between primary thread  16  and load bearing thread  17  prevents movement of the closure relative to the container  13  thus preventing gasket  20  from being damaged by the top load. In other words, downward force is transmitted to the load bearing thread  17  and on to container  13 . To facilitate the most efficient transfer of top load to the container  13 , closure thread  18  may operably have at least one flat load transfer surface  21 . 
     In the present embodiment and as exemplary only, the geometric relationship between the primary thread pitch “T 1 ” and vertical distance “T 2 ” should be maintained. “T 1 ” is the thread pitch of the primary thread, that is the distance between adjacent peaks of the primary thread  16 . “T 2 ” is the distance between the primary thread  16  and the load bearing thread  17 . Vertical distance “T 1 ” may be about twice the vertical differential “T 2 ”. Because “T 1 ” is larger than “T 2 ” it forms a target area, the area for starting a closure thread  18  on the container neck  13 . Also, if the pitch of the primary thread  16  and load bearing thread  17  are equal then vertical differential “T 2 ” will not vary and the closure thread  18  will be properly isolated therebetween. Preferably distance “T 2 ” is about {fraction (1/16)} of an inch (1.5875 mm) and “T 1 ” is about ⅛ of an inch (3.175 mm), however these measurements will vary if the pitch of the thread is varied. Preferably, the pitch is about six threads per inch. With this pitch, the closure can be removed in preferably one rotation. However, if the relationship between “T 1 ” and “T 2 ” varies, the closure thread  18  may not fit between primary thread  16  and load bearing thread  17 , or closure thread  18  may be loose and therefore allow gasket  20  to be damaged. 
     Connecting thread portion  21  is also shown in FIG. 2 connecting the primary thread  16  and load bearing thread  17 . The connecting thread portion  21  is molded integral with the primary thread  16  and load bearing thread  17 . Connecting thread portion  21  starts from below the starting point of the primary thread  16  and extends horizontally around container neck  13  until load bearing thread  17  begins. From that point load bearing thread  17  extends helically around container neck  13  parallel and equidistant to primary thread  16 . 
     For use of the present invention, the helical thread  18  of the closure enters target area “T 1 ” and continues along the helix moving above the connecting thread  21 . More specifically, an upper surface  18 ′ of helical thread  18  contacts a lower surface  16 ′ of primary thread  16  and the lower surface of helical thread  18  may contact connecting thread  21 . As the closure  11  rotates, helical thread  18  next enters a space between load bearing thread  17  and primary thread  16 . At that point, load bearing thread  17  contacts helical thread  18  on a bottom surface of the helical thread  18  while the top surface of helical thread  18  remains in contact with the lower surface of primary thread  16 . The closure is rotatably closed until the closure is sealed and secured to the container. 
     FIG. 3 shows the present inventive combination wherein the load bearing thread  117  is located on the closure  111  instead of the container  113 . A closure  111  is shown having top wall  112  generally of circular shape. Depending from the top wall  112  is a skirt  114  and load bearing thread  117 . Located on an interior surface  115  of the skirt  114  is a primary thread  118  for rotatably engaging a container thread  116 . Also located on the interior surface  115  of skirt  114  is a load bearing thread  117  which extends from container thread  116  near the top wall  112  of the closure  111 . 
     Load bearing thread  117  works with primary thread  118  to isolate container thread  116  of the container  113 . By isolating container thread  116  between load bearing thread  117  and closure thread  118 , the top load stacking force is transmitted through the closure  111 , to load bearing thread  117 , and to the container  113  efficiently without harming gasket  120 . 
     The vertical distance of the target area between closure threads  118  is about twice the vertical differential between load bearing thread  117  and closure thread  118 . This allows for a larger target area in which to start the closure. The load bearing thread  117  may preferentially be parallel to the closure thread  118  and preferably originates from a point beneath the starting point of the closure thread  118 . This ensures that there is no “play” between the container thread  116  and threads  117  and  118  and maintains a damage free the gasket  120 . 
     FIGS. 4 and 5 show two different embodiments of the load bearing thread being used on the closure. In FIG. 4 the closure thread  218  is shown having a transition area  218   a , the area where closure thread  218  begins, above the closure thread  218  and near the open end of the closure  211 . Since closure thread  218  does not extend as far as the load bearing thread  217  this allows a larger target area when the closure  211  is initially rotated onto a container. Space or groove  221  between successive rotations of load bearing thread  217  and closure thread  218  provides an area for a container thread to pass. As a closure thread enters the groove  221 , load bearing thread  217  transfers any stacking load from the closure  211  to a container through thread  217  thereby maintaining seal integrity. 
     FIG. 5 shows how the transition area  317   a  for load bearing thread  317  also can be manufactured below the closure thread  318  but has a starting point near the middle of skirt  314 . The load bearing thread  317  has a transition area  317   a  below the closure thread  318  as in FIG. 4, but does not extend the length of the closure thread  318  thus providing a large groove or target area  321  for starting the closure  311  on a container. As shown in FIG. 5 the transition area  317   a , where load bearing thread  317  begins, may be located near the middle of the skirt instead of the open end of closure  211 , as in FIG.  4 . 
     FIG. 6 shows another embodiment of a closure  411  having a load bearing thread  417  depending from a top wall  412  at the junction of top wall  412  and skirt  414  and being above a closure thread  418 . The load bearing thread  417  and closure thread  418  meet near the top wall  412  forming an area of increased thickness which transfers downward force to a container. In this embodiment the load bearing thread  417  starts from the top wall  412  and helically extends downward along an inner surface of the skirt  414  until it meets the closure thread  418  causing the enlarged area. Thus, FIGS. 4,  5 , and  6  show how the transition area can move from an open end of a closure to near the top wall of a closure. 
     FIG. 7 shows yet another embodiment where at least one load transfer protuberance  517  is integral with a skirt  514  for transferring a stacking load. The protuberance  517  is formed adjacent a closure thread  518  creating a space or groove  521  between the closure thread  518  and the protuberance  517 . As the closure  511  is turned onto a container, the closure thread  518  moves beneath a container thread until it is securely fastened. As the closure rotates, the container thread passes above the closure thread  518  and beneath the protuberance  517 . By passing the container thread through the groove  521  between the closure thread  518  and protuberance  517  vertical movement between the closure thread  518 , container thread, and protuberance  517  is diminished. The result is that a stacking or downward force is transmitted to the container structure preventing damage to the closure gasket. 
     Preferably, there are three protuberances  517  spaced equidistantly at about 120 degrees apart. However, any number of protuberances  517  may be used to transfer a stacking load to a container depending on the load, size of protuberance, size of closure threads, and the like. 
     The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications will become obvious to those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention and scope of the appended claims.