Patent Publication Number: US-2005124057-A1

Title: Two piece screw cap closure

Description:
FIELD OF THE INVENTION  
      This invention relates in general to two piece plastic threaded closures with removable body diaphragm for press fit installation on container openings with beaded rim. The invention relates to an improved low profile closure, which overlies a relatively tall container annular beaded rim. The invention relates to the position of the threads below the level of the container beaded rim for a lower closure profile on the container. The position of the cap threaded wall overlying the threaded body outer wall, braces the attachment of the closure to the container beaded rim for a strong mechanical attachment.  
     BACKGROUND OF THE INVENTION  
      One and two piece screw cap closures are commonly used to contain and dispense liquids from containers. Two piece closures commonly combine a body piece incorporating a threaded neck with an overlying threaded cap. The body piece typically has an annular recess or rim for attachment to the container, and may incorporate tamper evidence means such as a pull out diaphragm. The container or container cover is typically manufactured with an annular opening modified for subsequent attaching of the closure. Often the liquid contents are filled through the container opening, and the two piece closure is installed as part of the filling operation. Metal cans with a beaded rim for press fit of a two piece plastic closure is a common example. Cardboard dairy product containers with a thermally bonded plastic threaded closure is another recent example.  
      One piece threaded plastic and metal screw caps remain the most common closures due to low cost. One piece threaded caps may be applied directly to the container wherever the container opening is manufactured with suitable mating threads. Plastic and glass bottles with either plastic or metal threaded caps are common examples. Cap liners and gaskets are often required to close the voids between the cap and container to achieve a satisfactory liquid tight seal. The success of the one piece screw cap closure to retain the product without leaking depends upon the correct dimensional tolerance of both the cap and container threads, proper installation torque, and the elimination of voids in the joint.  
      Two piece closures are often preferred where the container opening thread dimensions vary due to manufacturing process variables, or where fabricating a threaded opening in the container is difficult. For example forming a threaded neck in metal containers is difficult due to the mechanical limitations of metal drawing. Plastic injection molded containers such as open head pails have molded threads which are subject to uneven post molding shrinkage leading to ovality of the threaded opening which can result in binding when threading the cap to the body. Plastic container manufacturing may be simplified by switching from a threaded opening to a simpler beaded rim, which results in savings in tooling and process scrap. Two piece threaded closures which combine ease of installation to the container with high performance and low cost are desirable.  
      One limitation of two piece threaded closures resides in the available height of the closure above the container surface where the cap must be sufficiently exposed to allow for easy gripping by hand for unthreading. If the cap is too high, it may be struck and dislodged during shipping and handling. A cap and body combination which has a low profile and strong attachment, but still allows for easy removal is desirable. Furthermore a two piece closure which incorporates a removable diaphragm in the body is a desirable tamper evident feature.  
      Threaded cap closures often incorporate a gasket or liner to close voids in the mechanical joint, and create a liquid tight seal between the container opening and the closure. Gaskets and liners add cost to the manufacture of closures, but allow for looser manufacturing tolerances by both the closure and container manufactured and assembled as a set generally allows for tighter tolerances and improved mechanical seal design. A body piece molded of relatively soft plastic aids in the establishing of a good seal between the relatively hard plastic of both the container and the closure cap, due to the spreading force of the relatively soft plastic between the hard plastic to fill in any voids.  
      It is an objective of this invention to provide an improved two piece threaded closure design for press fit installation on plastic containers with beaded rims. The improvements include the strong mechanical attachment and low profile of the closure which closely overlies a relatively tall container beaded rim.  
      It is a further objective of this invention to provide an improved two piece threaded closure utilizing a tapered or “V” shaped mechanical seal which substantially eliminates the need for cap gaskets or liners.  
      It is a further objective of this invention to provide an improved two piece threaded closure utilizing a mechanical seal between the closure cap and body which eliminates the need for cap gaskets or liners.  
     DESCRIPTION OF THE PRIOR ART  
      Prior art two piece threaded closures are common and typically comprise of a body portion incorporating a threaded neck for engagement with a removable threaded cap. The shape of the closures varies according to end use, the materials used and the method of attachment of the body piece to containers. Methods of attachment of the closure to the container include mechanical press fit, thermal bonding, adhesives and by other means. The closure cap is removable from the body at a later date for dispensing the product. Tamper evident features such as pull out diaphragms may be incorporated. Secure attachment is important for the performance of the container.  
      U.S. Pat. No. 5,267,675 illustrates a two piece closure that has a body which is designed for press fit into the container. An overlying threaded cap is shown removed for the attachment of the paint dispenser. The closure body is a mechanical press fit inside an annular container opening. The body threads are above the plane where the closure attaches to the container. This design has the disadvantage of being exposed to side impact, with the closure being easily dislodged.  
      U.S. Pat. No. 3,770,156 discloses the cross section of a container using a mechanical seal to replace traditional tubular rubber gaskets in plastic pails. The seal incorporates two flexible annular rings that are tapered to a flexible point. This design utilizes a seal between a semi-rigid plastic pail cover and similar plastic in the container body. This invention relates to two piece closures with a removable diaphragm, which are installed by mechanical press fit over a beaded rim.  
      Two piece plastic threaded closures, which are assembled to metal cans, are well known. Metal containers typically have a circular opening punched in the cover area. The edge of the opening may be reinforced by forming an annular lip or bead in the metal. The metal bead may be used as an attachment for a mating recess in the plastic closure body.  
      Prior art arrangements of two piece closures teach a closure body that is molded from a softer plastic relative to a harder plastic cup, due to the sealing ability of the softer plastic. The body-threaded neck is generally located in alignment with a body mating recess. The relatively harder plastic cap overlies the body threaded neck portion. The closure cap and body are typically pre-assembled by being threaded together. During installation the closure is positioned so the body recess aligns with the container opening rim. The closure and container are forced together with the body recess and typically sized to expand over and securely grip the container rim. In this arrangement the container is now sealed for shipment. The threaded cap can later be easily removed and resealed by the end user. Limitations on this design are the relatively high profile of the closure above the container, which may be struck and dislodged during shipment. It is desirable to have a closure which has a low profile.  
      A closure from Reike (trade name) on the other hand has a relatively low profile but the securing means does not extend much beyond the beaded rim.  
      Other prior art devices are shown in De 42 40 485 C.  
      Generally speaking the body recess in such prior art arrangements are limited by the size of the beaded rim that can be formed in the metal. This limits the mechanical engagement and seal performance that can be achieved between the container and closure. It is desirable to increase the relative height of the opening rim and deepen the body recess for better attachment and seal performance. The taller opening rim can easily be achieved in the manufacture of plastic injection molded and blow molded containers.  
      This invention relates to a two piece closure with a removable diaphragm, which is installed by mechanical press fit over a beaded rim.  
      In this invention, injection molded and blow plastic containers with relatively tall opening with beaded rims have been identified as suitable candidates forte improved two piece threaded closures.  
     SUMMARY OF THE INVENTION  
      This invention relates in general to two piece plastic threaded closures with removable diaphragm for press fit installation on container openings with beaded rim. More specifically the invention relates to the attachment of the closure to the container beaded rim using both a relatively tall inner wall and outer skirt, the outer skirt incorporating the body thread. The invention also relates to the position of the threads below the level of the container beaded rim for a lower closure profile on the container. The position of the cap threaded wall overlying the threaded body skirt, braces the attachment of the closure to the container beaded rim for improved seal performance. 
    
    
     DRAWINGS  
       FIG. 1  is a side and cross-sectional view of the two piece threaded closure before installation on a container cover.  
       FIG. 2  is a side and cross-sectional view of the two piece threaded closure after installation on a container cover.  
       FIG. 3  is a side and cross-sectional view of the closure body  
       FIG. 4  is a top view of the closure body  
       FIG. 5  is a side and cross-sectional view of the closure cap  
       FIG. 6  is a top view of the closure cap  
       FIG. 7  is a sectional view of a typical container cover opening  
       FIG. 8  is a sectional view of an optional container opening with neck ring  
       FIG. 9  is a partial enlarged cross-sectional view of the two piece threaded closure after installation on a container cover. 
    
    
     LIST OF DRAWING NUMBERS  
      Number Description  
     
         
           1  container cover  
           2  cover opening rim  
           3  rim bead  
           4  two piece threaded closure  
           5  closure body  
           6  body pull out diaphragm  
           7  diaphragm pull ring  
           8  body inner wall  
           9  body inner rim  
           10  body top wall  
           11  body outer wall  
           12  body thread  
           13  frangible web  
           14  annular body recess  
           15  annular rim recess  
           16  closure cap  
           17  cap top  
           18  cap seal projection  
           19  cap lugs  
           20  cap outer wall  
           21  cap thread  
           22  sealing recess  
           23  container  
           24  container neck ring  
           25  thread face  
           25 ( a ) lower face  
           25 ( b ) upper face  
           26  body outer rim  
           27  central axis  
       
    
     DESCRIPTION OF THE INVENTION  
      Like parts shall be given like numbers throughout the figures.  
       FIG. 1  illustrates a two piece threaded closure  4  before installation on container cover  1 . The closure  4  generally comprises a closure body  5  made of soft flexible plastic (i.e. low density polyethylene (LDPE)) or the like, and a closure cap  16 , made of semi-rigid plastic (for example high density polyethylene (HDPE)) or the like. The body  5  and cap  16  are co-axially disposed about central axis  27  and secured in threaded assembly by body thread  12  and cap thread  21 .  
      A variety of thread types can be used in this invention. In one embodiment buttress threads nave been favorably used as shown providing a strong fit. Furthermore there is a small gap which in one example can be in the order of up to 0.100 of an inch between the outer lip of the buttress threads and the body outer wall  11  and top outer wall  20  respectively, which accommodates any ovality of the annular shape of the body outer wall  11  and cap outer wall  20  so as to facilitate the treading and unthreading of the closure cap  16  to closure body  5 , and minimize binding of the parts.  
      Furthermore the buttress threads each present a relatively wide thread face  25  for strong threaded engagement therebetween. More specifically the body outer wall  11  presents buttress threads having a relatively wide lower face  25 ( a ) while the cap outer wall  20  prevents buttress threads having a relatively wide upper face  25 ( b ).  
      As is shown in greater detail in  FIG. 9 , closure body  5  is comprised of a body pull out diaphragm  6  attached to a diaphragm pull ring  7 . The diaphragm  6  is attached by an annular frangible web  13  to the annular body inner wall  8 . The inner wall  8  is generally cylindrical in shape and terminates in body inner rim  9 . A body top wall  10  beginning near body inner rim  9  extends generally radially outward from the body inner wall  8 , and leads to body outer wall  11 . Outer wall  11  is cylindrical in shape, and lies racially outside of body inner wall  8 . The inner wall  8 , top wall  10 , and body outer wall  11 , together form an annular body recess  14  on one side of the body top wall  10  and an annular rim recess  15  so as to facilitate the treading and unthreading of the closure cap  16  to closure body  5 , and minimize binding of the pasts, sized to attach to the container cover  1 .  
       FIG. 2  is a side and cross-sectional view of the two piece threaded closure after installation on container cover  1 . The container  1  presents a cover opening rim  2  having a generally upstanding peripheral edge with a rim bead  3  adapted to be received or captured by the annular rim recess  15  in a manner to be more fully described herein. As shown in  FIG. 2  the rim bead  3  is outwardly bulbous in one embodiment of the invention.  
      As shown in greater detail in  FIG. 9  the generally cylindrical inner wall  8  braces against cover opening rim  2  and body top wall  10  overlies rim bead  3 . During installation, the body outer wall  11  expands generally radially outwardly (i.e. the diameter expands) as rim bead  3  passes along body annular recess  14  and into the annual rim recess to be captured therein. After installation, the body outer wall  11  relaxes to a smaller diameter and underlies rim bead  3 . The cap outer wall  20  overlies and braces the body outer wall  11  against rim bead  3  to further resist removal of closure  4  from container cover  1 .  
       FIG. 3  specifically shows the body inner rim  9 , body top wall  10  and body outer rim defining a notch or sealing recess  22  which is adapted to receive cap seal projection  18  when the cap  16  is threaded to the closure body  5 . As the cap  17  is threaded to the body  6  the relatively soft plastic of body  5  “gives” and creates a substantially tight seal, which seals quickly, rather than gradually, and acts as a gasket.  
       FIG. 4  is a top view of the closure body  5 . Pull ring  7  is used to remove pull out diaphragm  6 .  
       FIG. 5  is a side and cross-sectional view of the closure cap  16  having top  17 .  
       FIG. 6  is a top view of the closure cap  16 . A plurality of cap lugs  19  are used as finger grips to assist the installation and removal of cap  16 . Cap seal projection  18  is designed to engage with body inner rim  9  and body outer rim  26  to create a seal.  
       FIG. 7  is a side and cross-sectional view of the opening in a typical container cover  1 . A cover opening rim  2  which is generally cylindrical in shape terminates in a rim bead  3 .  
       FIG. 8  is a side and cross-sectional view of an optional container  3  with neck ring  2  and rim bead  3 . An annular container neck ring  24  may be used to support the container  23  during the installation of closure  4 .  
       FIG. 9  is a detail side and cross-sectional view of the two piece threaded closure after installation on container cover  1 .  
      The assembly shown creates a low profile closure, resisting dislodgment when accidentally struck. Moreover the seal and closure is stronger and more robust.  
      Various embodiments of the invention have now been described in detail.  
      Since changes in and/or additions to the above-described best mode may be made without departing from the nature, or scope of the invention, the invention is not to be limited to said details.