Abstract:
A closure system for molded plastic containers having a threaded container neck, the closure system comprising a screw cap having internal threading constructed for threaded engagement with the threaded container neck, a gasket, means for retaining the gasket on the screw cap and an abutment surface integrally formed in and extending substantially radially from the container neck for sealably contacting the gasket, wherein the screw cap and the abutment surface are constructed so that downward axial rotation of the screw cap is effective to seal the gasket against the abutment surface.

Description:
FIELD OF THE INVENTION 
     The present invention relates, in general, to closure systems for molded plastic containers. In particular, the present invention relates to closure systems for molded plastic containers containing sterile fluids and having a cap associated therewith. 
     BACKGROUND OF THE INVENTION 
     Various food, medical and household products are presently packaged in molded plastic containers. Most of these containers include a dispensing port, and a closure system which creates a barrier for containing and/or protecting the contents of the container until the contents are to be used. Presently, many of these closure systems employ caps which are adapted to be easily removed. In particular, molded plastic containers are used to dispense sterile medical fluids for use in various medical procedures. For example, intravenous solution containers are used to administer parenteral solutions to a patient. Other medical containers are used to dispense irrigating fluids to a surgical site. Still other medical containers are used in enteral nutrition, inhalation, nebulizer, orthoscopic, mirror defogging, and x-ray preparation applications. 
     These medical containers have a common purpose of maintaining the sterility of their contents during manufacture, shipping, storage and dispensing. A critical portion of these containers is the closure system. The closure system must form and maintain a sterile barrier at a cap/container interface. This sterile barrier must remain intact from the time it is established until the time the container is intentionally opened for use. At the same time, these containers must be easily opened so that the contents of the container may be dispensed at the time of use. 
     The manufacture of medical containers typically includes a sterilization process such as autoclaving which subjects the container and contents to high temperatures typically in the range of approximately 118-121 degrees C. These temperatures can cause the pressure inside the container to be elevated above the pressure existing outside the container. Also, as the container is being cooled down from sterilizing temperatures, the pressure inside the container may drop below the pressure existing outside the container. The sterile barrier must be capable of withstanding these pressure differentials, to prevent air from any non-sterile environment which may exist outside the container from being drawn into the container during these processes, in order to maintain the sterile barrier. 
     As the contents of a container are being dispensed, the contents may come into contact with portions of the exterior of the container, therefore, it is often desirable that these areas also remain sterile. For this reason, the sterile barrier is typically located such that an exterior portion of the container adjacent to the dispensing port, including any threadings on the exterior of the container neck, is positioned between the sterile barrier and the contents of the container. In this way, the sterility of an external portion of the container can be maintained. 
     One means of providing a sterile barrier at a cap/container interface is to place a resilient gasket between the cap and the container and to exert compressive forces to sandwich together the cap, gasket and container whereby a sterile barrier may be established. Nevertheless, continuing problems remain in such closure systems in preventing the breach of the sterile barrier. Inherent factors can create difficulties in the establishment, maintenance and reliability of the sterile barrier. For example, typically the gasket is a separate component of the closure system, which requires that two critical sterile barriers be established and maintained; one at a cap/gasket interface and a second at a gasket/container interface. The reliability of such closure systems, which are dependent on the maintenance of two critical sterile barriers, is lessened as both sterile barriers are subject to failure. Also, such closure systems typically are not constructed to minimize movement and/or expansion of a gasket in directions other than the directions of applied compressive forces. This can affect the integrity and the reliability of such a closure system. Also, dimensional variations due to molding tolerances of cap, container and gasket components can make such closure systems unreliable and prone to failure. 
     Therefore, it is desirable to provide a closure system which forms a sterile barrier having high integrity and operational reliability. It is desirable that the sterile barrier be located so that an external area adjacent to the dispensing port remains sterile. It is also desirable to provide a closure system which allows the container to be easily opened so that the contents of the container may be dispensed at the time of use. Furthermore, since closure systems are often used only once and are disposed of after use, it is desirable that the cost of manufacturing the closure system is relatively low. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention there is provided a closure system for molded plastic containers which is capable of providing a sterile barrier or seal having high integrity and operational reliability. Also, the present invention provides a sterile barrier which is located so that the sterility of an external area adjacent to the dispensing port can be maintained in a sterile condition. Also, the present invention provides a closure system which allows the container to be easily opened at the time of use and which can be manufactured economically. 
     Specifically, the closure system comprises a screw cap having internal threading constructed for engagement with threading located on the exterior of the container neck. The cap has a sidewall. Inner and outer annular rims are integrally formed and extend downwardly from the sidewall of the cap. A resilient compressible gasket is positioned between the annular rims. The gasket is designed to engage against an abutment surface integrally formed in and extending radially from the container neck, to establish a sterile barrier when the cap is rotated downwardly onto the container neck. 
     In a preferred embodiment, the gasket and cap are integrally formed in a single injection molding operation to create a unitary component. Also, the abutment surface is subjected to an ultrasonic treatment, called swaging, which smooths the molding seams created during the molding process, particularly along the points-of-contact made by the gasket with the abutment surface when the gasket is fully seated against the abutment surface. 
     Thus, in accordance with the present invention, a closure system is provided which forms a sterile barrier having high integrity and operational reliability, is easily opened at the time of use, and has a relatively low manufacturing cost. 
     Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the disclosed embodiments thereof, from the claims and from the accompanying drawings in which the details of the invention are fully and completely disclosed as part of this specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of the closure system of the present invention; 
     FIG. 2 is a side elevation view, partially broken away, showing in particular an upper portion of the closure system of the present invention; 
     FIG. 3 is a cross sectional, side elevation view of a portion of the closure system of the present invention, showing in particular a plug seal; 
     FIG. 4 is a cross sectional, side elevation view of a portion of the closure system of the present invention, showing in particular a knife seal; 
     FIG. 4 a  is an enlarged view of a portion of the closure system of the present invention, showing in particular the gasket area; and 
     FIG. 5 is a side elevation view of a portion of the closure system of a present invention, showing in particular a knurled cap. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     The closure system incorporating the present invention is typically used with medical administration systems having certain conventional components the details of which, although not fully illustrated or described, will be apparent to those having skill in the art and having an understanding of the necessary functions of such components. 
     Referring to FIGS. 1 and 2, closure system  10  generally comprises molded plastic container  12  including container shoulder  13 . Container  12  includes container neck  14  extending upwardly from container shoulder  13 . Container  12  has dispensing port  17  defined by pour lip surface  18  formed at container neck  14 . Helical external threading  16  is located on container neck  14 . Abutment surface  20  is integrally formed on, and extends substantially radially from, container neck  14  and is located between external threading  16  and container shoulder  13 . Closure system  10  further comprises screw cap  22  having helical internal threading  24  of proper size and construction for rotatable engagement with external threading  16  on container neck  14 . Screw cap  22  includes top wall  21  and continuous cylindrical sidewall  32  extending downwardly from top wall  21 . Inner annular rim  30  and outer annular rim  31  are integrally formed on, and extend downwardly from, sidewall  32  of screw cap  22 . Inner annular rim  30  has a diameter which is less than the diameter of outer annular rim  31 . Annular recess  33  is defined by inner and outer annular rims  30  and  31 . Closure system  10  further comprises gasket  36  which is retained on screw cap  22 . Gasket  36  may be retained on screw cap  22  by being positioned in annular recess  33  and held there by being pressure-fitted into place. Alternatively, gasket  36  may be retained on screw cap  22  other means, such as by being molded-in-place. Gasket  36  has a distal end which forms an angle of approximately 28°-38° relative to the top wall  21  of the screw cap  22 . 
     Container  12  may be manufactured by conventional molding procedures using a thermoplastic material such as polypropylene, polyvinylchloride, polyethylene terphthalate, butadiene styrene, acrylics including acrylonitrile, polytetrafluoroethylene, polycarbonates and other thermoplastics. Screw cap  22  may be manufactured by injection molding a thermoplastic material such as polypropylene, polyvinylchloride, polyethylene terphthalate, butadiene styrene, acrylics including acrylonitrile, polytetrafluoroethylene, polycarbonates and other thermoplastics. Gasket  36  may be fabricated from resilient compressible material such as rubber, butadiene, polytetrafluoroethylene (such as TEFLON®), or injectable thermoplastic elastomeric co-polymers (such as KRATON® or C-FLEX®). The materials used for the container  12 , screw cap  22  and gasket  36  should be selected from among materials compatible with the contents of the container, to prevent the materials from causing chemical changes to the contents of the container during storage and, also, to prevent the contents of the container from causing physical or chemical changes to the materials. 
     In a preferred embodiment as shown in FIG. 3, plug seal  40  extends downwardly from top wall  21  and coaxially with sidewall  32 , with plug seal  40  having a diameter which is less than the diameter of sidewall  32 . Plug seal  40  is configured to contact interior surface  19  of container neck  14 . Plug seal  40  functions to create a barrier to reduce the likelihood of contact between the contents of container  12  and an exterior portion of container  12  adjacent to dispensing port  17 , including external threading  16 , prior to the time the contents of container  12  are used. This contact might otherwise occur, for example, as a result of splashing caused by the handling of container  12  during shipping or storage. Plug seal  40  is constructed so that contact between plug seal  40  and interior surface  19  does not prevent engagement of gasket  36  with abutment surface  20  upon engagement of internal threading  24  in screw cap  22  with external threading  16  on container neck  14 . Also, abutment surface  20 , screw cap  22  and gasket  36  are constructed so that contact between gasket  36  and abutment surface  20  does not prevent a barrier from being created by plug seal  40  coming into contact with interior surface  19 , upon engagement of internal threading  24  in screw cap  22  with external threading  16  on container neck  14 . 
     In an alternate preferred embodiment, knife seal  50  extends downwardly from top wall  21  and coaxially with sidewall  32 , with knife seal  50  having a diameter which is less than the diameter of sidewall  32 . Knife seal  50  is configured to contact pour lip surface  18 . Knife seal  50  functions to create a barrier to reduce the likelihood of contact between the contents of container  12  and an exterior portion of container  12  adjacent to dispensing port  17 , including external threading  16 , prior to the time the contents of container  12  are used. Knife seal  50  is constructed so that contact between knife seal  50  and pour lip surface  18  does not prevent engagement of gasket  36  with abutment surface  20  upon engagement of internal threading  24  in screw cap  22  with external threading  16  on container neck  14 . Also, abutment surface  20 , screw cap  22  and gasket  36  are constructed so that contact between gasket  36  and abutment surface  20  does not prevent a barrier from being created by knife seal  50  coming into contact with pour lip surface  18 , upon engagement of internal threading  24  in screw cap  22  with external threading  16  on container neck  14 . 
     External threading  16  and internal threading  24  are constructed to establish sufficient contact between external and internal threadings  16  and  24  to establish a sterile barrier or seal at gasket/container interface  25 , located between gasket  36  and abutment surface  20 , and to maintain the sterile barrier from the time sterilization is established until the time the contents of container  12  are to be used. 
     In a preferred embodiment, container  12  is extrusion blow molded and is then subjected to a well-known treatment, namely ultrasonic treatment (sometimes referred to as swaging), which smooths the molding seams created during the molding process, particularly along the points-of-contact made between gasket  36  and abutment surface  20  when gasket  36  is fully seated against abutment surface  20 . 
     In a preferred embodiment of the present invention, container  12  and screw cap  22  are polypropylene and gasket  36  is polytetrafluoroethylene. Also, screw cap  22  and gasket  36  are molded simultaneously using a well-known technique. One such technique is a molding process know as two-shot injection molding. The use of a two-shot injection molding process causes screw cap  22  and gasket  36  to bond together thereby producing a unitary component. In a preferred embodiment, screw cap  22 , (including inner annular rim  30  and outer annular rim  31  integrally formed on sidewall  32  of screw cap  22 ) is produced by injection molding. Next, gasket material is injected as a “second shot” and gasket  36  is molded between inner and outer annular rims  30  and  31 . In an alternate preferred embodiment, gasket  36  is produced by injection molding. Next, screw cap material is injected as a “second shot” and screw cap  22  is molded onto gasket  36 . 
     Using two-shot injection molding to form gasket  36  and screw cap  22  can reduce the overall cost of the parts because the costs of handling, shipping, and stocking individually-molded gasket  36  and screw cap  22  parts may be avoided. Also, the cost of customized equipment which may otherwise be required to subsequently sort and assemble individually-molded gasket  36  and screw cap  22  parts may be avoided. Also, closure system  10  produced using the two-shot process can offer a reduced risk of a breach of sterility at a sterile barrier at cap/gasket interface  23  because the cap/gasket interface  23  is virtually eliminated when the materials used for screw cap  22  and for gasket  36  reflow and bond during the second shot of the process. Screw cap  22  and gasket  36  are essentially fused together. Also, the two-shot process can produce a closure system  10  in which dimensional variations which would otherwise affect the fit between gasket  36  and screw cap  22 , and which would otherwise make the closure system less reliable and more prone to failure, are negated by forming gasket  36  and screw cap  22  into a unitary component. 
     In a preferred embodiment, container  12 , screw cap  22 , gasket  36  and the contents of container  12  are assembled and then the assembly is sterilized. Thus, the contents of container  12  are sterilized along with that portion of the assembly which is located on the sterile side of the sterile barrier, including the interior of container  12  and an exterior portion of container  12  (including external threading  16 ) which may come in contact with the contents of container  12  during use. In an alternate preferred embodiment, screw cap  22 , gasket  36  and container  12  are sterilized and then closure system  10  is filled and assembled using aseptic procedures. 
     To attach screw cap  22  to container  12 , screw cap  22  is threadably rotated downwardly on container neck  14 , with engagement of internal threading  24  in screw cap  22  with external threading  16  on container neck  14 , until further downward movement of screw cap  22  is retarded as compressed resilient gasket  36  comes into resistive contact with abutment surface  20 . Inner and outer annular rims  30  and  31  retain gasket  36  and minimize movement and expansion of gasket  36  in directions other than the directions of applied compressive forces. Undesirable movements of gasket  36  are thereby eliminated and closure system  10 , having high integrity and operational reliability, is provided. 
     Screw cap  22  may be removed from container  12  so that the contents of container  12  may be used. Subsequently, screw cap  22  may be reseated onto container neck  14 . 
     Closure system  10  may include heat shrinkable outer member  60  which is placed external to container  12  to envelop the cap/container interface, thereby providing a tamper evident seal. 
     FIG. 3 illustrates a preferred embodiment of closure system  10  incorporating the present invention in which a distal end  38  of gasket  36  forms an angle “x” of between approximately 28 and 38 degrees relative to top wall  21  of screw cap  22 , which, when brought into compressive contact with abutment surface  20 , results in the establishment of compressive forces in both vertical and non-vertical directions. Also, a proximal end  39  of gasket  36  forms an angle “y” of approximately 35 degrees relative to top wall  21  of screw cap  22 . These angles can increase the effectiveness of the sterile barrier provided by closure system  10 . 
     In a preferred embodiment, the exterior surface of sidewall  32  contains knurls  70  so screw cap  22  can be removed more easily at the time of use. 
     From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It will be appreciated that the present disclosure is intended as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.