Abstract:
A modular valve assembly provides an airtight, shockproof, leakproof and evaporation proof closure effective for sealing engagement with the neck or outlet of a flexible or reducible container. The modular valve assembly is effective in preventing: (1) leakage of fluids from the container due to vibration or changes in temperature or pressure; (2) any backflow or reentry of contaminants through the valve assembly, including air; and (3) evaporation of fluid from the container. If the fluid initially is sterile, the closure maintains the sterility of the remaining fluid in the container during and between dispensings of the fluid. Thus, the modular valve assembly extends the useful life of the fluid in the container to its shelf life. Although the user makes many dispensings from it, the container behaves as though she or he had never opened it. Thermostable fluids delivered through this modular valve assembly have no need for preservatives or refrigeration.

Description:
BACKGROUND OF THE INVENTION 
     The field of the invention relates generally to a valve assembly for one-way flow. In particular, the field of the invention relates to a modular valve assembly for sealing engagement in the neck of a flexible container, forming a closure that is airtight, shockproof, leakproof and evaporation proof. This closure is effective against leakage of fluids due to vibration as well as changes in temperature and pressure, for preventing any backflow or reentry of contaminants through the valve assembly, including air, or evaporation of fluid from the container. Moreover, if the fluid initially is sterile, the shockproof closure maintains the sterility of the remaining fluid in the container during and between dispensings of the fluid. 
     In dispensing sterile fluids from a container wherein the container has an extended period of use-life, it is important to prevent any back flow of contaminants into the container during and after the dispensing operation has been carried out. Contaminants in the form of materials originating from outside of the valve assembly and container may include microorganisms, atmospheric gases, moisture, dust or the like. If the sterile fluid is contaminated it can affect the quality, concentration of constituents, potency and even safety of the product. In many cases, it is highly desirable to prevent leakage and evaporation of the contents of the container between uses. At best, leakage will cause sanitary problems as well as the loss of some or the entire product. At worst, evaporation of a volatile solvent will alter the concentration of the remaining solute. This could prove dangerous. 
     If a container of a sterile fluid has a one-time use and the user does not intend to dispense fluid over an extended period, the problem of contaminants flowing backward into the container usually does not exist. In one known liquid handling container disclosed in U.S. Pat. No. 2,715,980 to Frick, the valve mechanism involves a valve body with a central port extending through the valve body and with branch ports extending from the central port to the outside surface of the valve body. An expansible sleeve, such as a sleeve of a rubber-like material, encloses the outside surface of the valve body preventing flow from the branch ports. When a fluid is to be dispensed, it flows through the central port and then through the branch ports causing the sleeve to expand and permitting the fluid to flow out around one end of the sleeve. During such flow, it is possible for contaminants to flow into the expanded end of the sleeve and then through the branch ports and central port, back into the container. An effective blockage of contaminant back flow into the container is not available. 
     Kulle in U.S. Pat. No. 4,346,704 discloses another valve incorporating an elastic tube or sleeve. A solution is dispensed through a central tube or channel to branch ports, which deliver the fluid to the inside surface of an elastic sleeve or tube. When the fluid is pressurized, it displaces the elastic tube outwardly permitting flow from the branch ports outwardly from the end of the sleeve. The Kulle device is primarily intended for a one-time use, such as in dispensing an anesthetic. There is no particular problem with a return flow of contaminants into a container or leakage of contents from the container because of such one-time use. The Kulle device is intended to deliver anesthetics at high flow rates and low pressures so that accurate dispensing is possible. 
     However, such conventional valves lack mechanisms for repeatably locking a seal to a container of sterile fluid so that once opened, the container does not need to be refrigerated nor are preservatives required to safeguard the integrity and concentration of the fluid. The majority of compression-type seal applications are static in nature, providing an effective seal only until the container is first opened. This means the components of the seal do not interact to reseal the container against external matter. Once the user opens a container of fluid, the integrity of the fluid degrades and has a limited use life. In addition, there is currently no mechanism for providing a reusable, locking seal for a container of fluid such that the seal is invariantly secure against vibration as well as against changes in temperature and pressure during long term storage and reuse. 
     Newton et al., U.S. Pat. No. 5,226,568, purports to disclose a resealable valve and cap for preventing backflow of air into a deformable container. However, unintentional compression of the container by dropping or squeezing, or variation in temperature and pressure may enable excursion of fluid to reside between the seal and cap. In addition, this system is not able to compensate for over-pressure of the cap or friction and abrasion applied by the cap against the seal, which ultimately degrades the seal and may open the contents of the deformable container to contamination. 
     Therefore, what is needed is a closure that provides a repeatable locking seal for a container of fluid, is shockproof, leakproof, contamination proof and evaporation proof; one that is immune to changes in pressure and temperature and is able to maintain the integrity of the fluid by preventing the unwanted passage of matter in either direction between uses. Such a seal would extend the use life of a product essentially to the limit of its shelf life. 
     The shelf life defined herein is the length of time an unopened product, such as a packaged food, a chemical preparation, or a pharmaceutical product, may be stored without deteriorating and remain effective for use. The use life or useful-life is the length of time after opening the container or package, i.e., its first use, that a product may be used, without deteriorating and remain effective for use. Most fluids are sensitive to contact with the environment and degrade due to hydrolysis, oxidation and microbial attack. In most cases, the use life is considerably shorter than the shelf life. Therefore, what is needed is a container closure that extends a fluid&#39;s use life up to its shelf life, a closure that behaves throughout multiple deliveries as if its associated container had never been opened. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a modular valve assembly for effecting a sealing engagement with the neck of a flexible container enabling the easy dispensing of fluid while preventing any leakage, evaporation, or back flow of contaminants, including air and microbes, through the valve assembly into the container holding the remaining fluid. Thermostable fluids delivered through this assembly have no need for preservatives nor require refrigeration. Another aspect of the invention provides a valve assembly that seals to the interior and exterior surfaces of a container over a wide range of tolerances without concern for the presence of flash or other nonconformities on the neck of the container. 
     An aspect of the invention effects a primary seal on top of a neck of a flexible container. It also effects a secondary seal on the interior surface of the container and a locking seal on the exterior surface or threads of the neck of the flexible container. The flexible container can be a squeeze bottle, a plastic tube, a syringe or piston, a pouch, or a bag. The container also may be a combination two or more of these. For example, the container having flexible walls can enclose a plastic bag wherein the bag attaches to the neck of a container or any other containment vessel. Such vessel is characterized by a compressible or volumetrically reducible reservoir so that flexible walls for applying a pressure will expel or cause a fluid to flow. 
     The valve assembly comprises a seat in cooperative engagement with a seal, a segmented retainer and a threaded or snap cap. As the cap is seated, the retainer segments close and transmit lateral compressive forces from the closure of the cap to all sealing surfaces of the seal. The geometry of the seat, seal, retainer and cap interact to ensure that residual fluid is forced progressively outward into a recess between the cap and the tip region of the seat. When the cap is in the seated or closed position, the compressive forces provided by the cap against the retainer, seal and seat, respectively provide a shockproof seal of the fluid, which is effective against the ingress or egress of matter at a molecular level, to include even air or volatile solvents. The extent of the seal is such that the valve assembly is immune to variations of pressure and temperature and the container can be accidentally squeezed, dropped or subjected to severe vibration without loss of fluid integrity. 
     In accordance with an aspect of the present invention, a valve assembly includes an elongated, tapered seat with an elastomeric seal laterally enclosing the outside surface of the seat. The seat defines a fluid flow path through an exit port or orifice located in the side of an upper tapered portion. Pressing the walls of the flexible container activates fluid flow. Fluid passes through the seat through the exit port and into the space between the outside surface of the seat and the elastomeric seal. The seal and seat are configured to create a progressive seal in a reverse direction for the excursion of fluid to prevent fluid from reentering the container. The cooperative engagement of the cap, retainer, seal and seat respectively provide a shockproof sealing closure when the cap is in the seated position. 
     Another aspect of the invention provides a container neck closure that can be manufactured easily using existing blow molding, injection molding and other molding processes. The components, seat, seal, retainer and cap, are molded separately, assembled, and snap together. These components can be designed to fit conformably over the neck of a container to form a dispensing and delivery system. While the seal functions with precise tolerances and can effect a substantially complete seal of the fluid in the container, the assembly includes a base having an interior and exterior seal for engaging the inner and outer diameter of a container neck. Thus, the assembly can be adapted for variations in tolerances associated with blow molding and high volume production of containers. 
     The seat is tapered over most of its length, which makes it simple to assemble with the associated seal and retainer. Only about 0.050 cm of seal length is needed to create a reliable barrier. Thus, only a short cylindrical section of the seat is needed to mate conformably against the seal to form an effective barrier. The seal below the exit port is significantly thicker than the portion of the seal above the exit port. This causes any displaced fluids, after closure, to move only toward the aperture at the tip of the seat. 
     A compressive load provided by the retainer holds down both seal and seat. The retainer has a plurality of segments, typically four to six, outboard of the seal. These segments are displaced inwards toward the seal when a user closes the cap. The tips of the segments further progressively compress the seal above the exit port, preventing backflow. Securing the cap to the retainer compresses the segments of the retainer firmly locking the seal against the seat. This action prevents evaporation or the accidental dispensing of fluid. Alternatively, it is possible to have only a single segment or arm that compresses the exit port area only and thus creates an effective seal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following descriptions, appended claims, and accompanying drawings, in which: 
     FIG. 1 is a cross-sectional diagram of a modular valve assembly engageably fitted over the neck of a flexible container in accordance with an aspect of the invention. 
     FIG. 2 is an enlarged cross-sectional diagram of the valve assembly and cap showing details of the sealing surfaces. 
     FIG. 3 is a perspective drawing of a seat in accordance with an aspect of the invention 
     FIG. 4A is a side view of the components of a valve assembly in accordance with an aspect of the invention. 
     FIG. 4B is a perspective drawing of the components of a valve assembly in accordance with an aspect of the invention. 
     FIG. 5 is a cross-sectional diagram of an alternative embodiment of the valve assembly, with the cap in both an unseated and a seated position, in accordance with an aspect of the invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a modular valve assembly  100  affixed to the neck  105  of a container  102 . Valve assembly  100  comprises a seat  104  defining a fluid flow path from the container through an exit port  106 . The seat  104  is cooperatively engaged with an elastomeric seal  108 , which is in turn held in engagement against the seat by a retainer  110 . A cap  112  is provided with an engagement means such as a series of threads  114  around its base portion for interengagement with mating threads of the retainer  110 . The cap  112  applies compressive forces to the seal  108  through the retainer  110 . The retainer has a plurality of segments  116  in its upper portion as shown in FIG.  4 A. The retainer preferably has four to six segments outboard of the seal  108 . These segments are displaced inwards toward the seal  108  when a user tightens the cap  112  into a seated or closed position. As shown in FIGS. 1 and 2, the segments,  116  of the retainer  110  compress the seal  108  above the exit port  106  and perform two functions. Due to the geometry of the upper portion of the seat  104  above the exit port  106 , the tips of the segments circumferentially compress the seal above the exit port preventing fluid from being accidentally dispensed when the cap is secured. 
     Secondly, the segments of the retainer apply a compressive force to the seal to force excess fluid from the exit port  106  outward progressively toward the distal tip of the seat  104  thereby preventing backflow of fluid into the container  102 . 
     As shown in FIG. 2, an aspect of the invention shows an elongated, tapered seat  104  with a dispensing or exit port  106  in the side. The base of the seat has a first downwardly projecting annular portion or surface  118 , which forms a sealing engagement with the interior surface  120  of the neck of the flexible container  102 . The base of the seat  104  has a second downwardly projecting annular portion or surface  122  provided with a means for sealing engagement with the exterior surface of the neck of the container. A series of threads  124  provide sealing interengagement with one or more conformably placed threads  126  on the exterior surface of the neck of the flexible container  102 . However, the means for sealing engagement also can comprise a locking ratchet mechanism  128  as shown in FIG. 3, which positively engages a congruent series of ratchet projections  129  on the neck  105  of container  102  as shown in FIG.  4 B. 
     Referring to FIG. 2, the base of the seat  104  also has a shoulder portion  130  linking the first and second downwardly projecting annular portions or surfaces  118  and  122 , respectively, such that the seat  110  also sits on top of and in sealing engagement with the top surface  132  of the neck  105  of the container  102 . Thus, two side surfaces  118 ,  122  and the shoulder  130  of the seat sealably engage the neck of the container. This design provides a primary sealing surface  132  at the neck of a container and secondary sealing surfaces on the interior and exterior surfaces of the neck  105  of container  102 . The threaded engagement between the seat  104  and the neck  105  of container  102  enables the seat  104  to provide a complete seal with a container over a relatively wide range of tolerances, which one would expect with high volume production of blow molded containers. In accordance with an aspect of the invention, the seat provides a substantially impermeable fail-safe seal around both the interior and outer surfaces of the neck of a container without regard to the existence of flashing, differing tolerances or other non-conformities in the neck of the container. 
     The seat  104  is tapered over most of its length thereby facilitating ease of assembly of the seal  108  and retainer  110  by snap engagement or press fitting the seal  108  and retainer  110  over the seat. This is particularly advantageous for low cost, high volume assembly. FIGS. 4A and 4B show the assembly of the components. The seat  104  typically comprises a hard plastic material such as an epoxy. High impact machinable epoxies are ideal for durable wear or replacement machine parts and other similar applications. This material is a good substitute in applications where tough plastic parts are used. It is very tough, has high impact resistance and can be molded as the finished part or machined in secondary operations. Variations are available for temperature environments to 400° F. 
     The seal  108  comprises an elastomeric material, such as silicone, polyurethane and C-flex, which is press fit over the seat  104 . Polyurethane is a preferred material, since it is one of the toughest, most abrasion resistant, engineered elastomers available. It outperforms all other rubber type materials in mechanically abusive environments. It can be manufactured to have a durometer as high as 90 Shore D. Aliphatic polyurethane is also water, UV and ozone resistant. This material is ideal for continuous use in a harsh environment. 
     The seal also can comprise a silicone material. Silicones provide a non-stick surface for many processes. FDA approved and class VI medical materials are available. Silicones maintain their flexibility at low temperature. They have low compression set, and outstanding resistance to high temperature, sunlight, oxidation, ozonolysis, and corrosion. Standard silicones are temperature rated from −1500° F. to 650° F. High performance silicones can operate in a continuous environment from −150° F. to 650° F. with excursions to 850° F. 
     The seal  108  is provided with an annular base  140 , that conformably engages against the base of seat  104 . The sides of the seal  108  between its base  140  and the seat exit port  106  are much thicker than the upper portion of the seal  108  above the exit port  106 . This configuration delivers a constant compressive force against the portion of the seat below exit port  106  in spite of changes in temperature, pressure, or normal seal wear. 
     The flexibility of the seal material enables it to conform to mating surfaces of the seat, thereby forming a complete seal closing off the flow of fluid between the seal and seat except when the valve is in the open state. The seal  108  is constructed to be thinner and sharply tapered above the exit port  106 . The thickness of the seal at this point is selected to determine a desirable cracking pressure for enabling the fluid to flow out of the exit port and along the tapered tip of the seat when the desired pressure is applied to the walls of the flexible container to dispense the fluid. 
     The seal  108  and seat  104  are produced from molds. The molds are machined in a circular lay pattern to a surface smoothness equivalent to the smoothness of diamond. Asperities and nonconformities on the mold surface, which form the sealing surfaces of the seal and seat are limited to a range of 0 to 30 microinches and preferably to a range of 0 to 5 microinches. The mold is formed such that there are no parting lines in the parts of the mold that form the sealing surfaces of the seal and seat. Thus, the asperities or imperfections in the sealing surfaces of the seal and seat are limited to the foregoing ranges also. 
     A retainer  110  is press-fit over the seal  108  and seat  104 . The retainer  110  holds the seal  108  in place against the seat  104  and applies a strong compressive force against the sides and base of the seal  108  and seat  104  to effect a positive, impact proof seal between the seal  108  and seat  104  when the cap  112  is threaded in the seated or closed position. The seal thus produced is effectively impermeable and is temperature and pressure invariant. 
     The retainer  110  is provided with a series of threads  142  on its outer surface for engaging with the congruent interior threads  144  of the cap  112 . The seating of cap  112  provides a strong compressive force, through an interior shelf  151 , against the sides of the retainer  110  and a downward compressive force by interior shelf  152  at shoulder  150  of the retainer. The threading action of the cap causes the application of strong lateral forces to compress the sides and upper portion of the retainer  110  strongly against the seal  108 . 
     The retainer  110  includes a base portion  146  for conformably holding and fitting over the base  140  of the seal. The base  146  of the retainer  110  is also held in place by an annular rim  148  of the seat  104  as shown in FIG.  2 . The retainer  110  comprises any suitable resilient, compressible plastic material that can absorb and transfer compressive forces applied by seating the cap. The retainer holds together the seal and seat in a substantially invariant alignment and translates the compressive forces applied by the cap against the seal and seat to provide a shockproof, leakproof seal when the cap is threaded in place. The substantially smooth sealing surface formed between the seal and seat (each having surface asperities limited to a range of preferably 0 to 5 micro-inches) provides substantially a monolayer of fluid between the sealing surfaces, which prevents the motility of microorganisms and is effective against the intrusion of airborne contaminants and air. The retainer  110  also includes a shoulder portion  150  for conformably engaging an interior shelf  152  of cap  112 . The interior shelf  151  comprises a convex annular surface provided on the interior circumference of the cap  112  for engagement against the segments  116  of the retainer when the cap approaches the last quarter turn in the act of being threaded onto the retainer. The convex annular surface provided in the cap compresses the segments  116  of the retainer to provide a complete seal which is shockproof, leakproof, evaporation proof and resistant to changes in temperature and pressure. 
     The interior shelf  152  transfers a downward compressive force to the base  140  of the seal when the cap  112  is in the seated position. The retainer  110  is provided with a projection of excess material  154  for conformable fit engagement with a congruent depression of the seat  104  for snap engagement for press fitting. The retainer also can be ultrasonically bonded to the seat at projection  154 . The seat, seal and retainer also can be heat-sealed. 
     The projection  154  comprises a point of excess material in the base of the retainer  110 . Projection  154  acts as an energy director that is receptive to ultrasonic heating. When ultrasonically heated to its melting point, projection  154  provides a material flow between the adjacent surfaces of the shoulder portion  146  and rim  148  of the seat  104  to form an airtight seal between the retainer  110  and seat  104 . 
     In a preferred mode of assembly, as shown in FIGS. 4A and 4B, the seal is press fit over the seat. The retainer is then ultrasonically bonded to the seat. 
     As shown in FIGS. 2,  4 A and  4 B, the taper of the seat  104  increases substantially above the exit port  106 . This angle enables progressive excursion of fluid away from the exit port  106  when the retainer  110  and tapered portion of the seal  108  apply compressive forces against the seat  104 . The taper of the seat is optimized to provide a droplet of desired volume at a distal end of the seat body. 
     Referring to FIGS. 4A and 4B, retainer  110  includes a plurality of segments  116  separated by spaces which are necessary to accommodate the taper of the seat  104  and enable flexion of each of the segments  116 . As the cap is seated, the segments  116  are compressed together to provide a progressive seal for the excursion of fluid in a downstream direction away from exit port  106  in response to the seating of the cap  112 . 
     In operation, the compressive force exerted by the retainer  110  against the seal  108  locks the seal  108  strongly against the mating surfaces of the seat  104  and insures a positive seal. When the cap  112  is seated onto the retainer  110 , the retainer  110  transmits the compressive forces applied by the seated cap  112  to all sealing surfaces to insure consistent sealing of the container  102  against evaporation, backflow and leakage due to vibration as well as changes in temperature and pressure. The tapered configuration of the seat  104  interacts with the seal  108  and retainer  110  to create a progressive seal for the excursion of fluid in a downstream direction away from the exit port upon closure and restricts the backflow of excess fluid and environmental contaminants. The retainer  110  transmits the pressure of the seated cap to all sealing surfaces to insure consistent sealing of the container against evaporation, backflow and leakage due to vibration as well as changes in temperature and pressure. 
     FIG. 2 shows the cap  112  installed, the retainer  110  compressed to form a locking seal between seal  108  and seat  104  under pressure. As the engagement of the threaded cap  112  increases the compressive forces applied to the retainer  110 , the retainer moves conformably against the seal  108 . 
     To dispense the fluid, the cap is removed and pressure is applied to the walls of the container  102 . The amount of cracking pressure required to move the seal off of the seat at the exit port  106  is determined by the frictional force of the seal on the sealing surfaces and the durometer and modulus of elasticity of the seal material. The seal material can be engineered by well-known techniques to have a cracking pressure that is optimal for the particular viscosity of the contained fluid. 
     When the internal pressure in the container  102  exceeds the frictional forces between the seal  108  and seat  104  at the exit port  106 , the fluid is directed downstream along the tapered end of the seat  104 . When the internal pressure in container  102  is released, the compressive force applied by the seal  108  against the tapered end of the seat  104  will progressively form a seal tight engagement between the seal  108  and seat  104 . The cap  112 , acting in combination with the retainer  110 , seal  108  and seat  104  provides a compression seal, preventing migration of liquids, gases or solid contaminants, whether by diffusion, osmosis, or motility of microbes, or combinations of these, inanimate or animate, across the sealing surface formed between the seal  108  and seat  104 . 
     The flexibility of the seal material enables the seal  108  to conform to mating surfaces of the seat  104 , thereby closing off the flow of fluid. The retainer  110  transmits the pressure of the seated cap  112  to all sealing surfaces of the seal  108  and seat  104  to insure consistent sealing of the container. 
     The compressive force exerted against the seal  108  by the retainer  110  on the mating surfaces insures a positive seal, even against vibration as well as against changes in temperature and pressure so as to maintain the integrity of the remaining fluid by preventing the entry of environmental contaminants. 
     Under high pressure, the seal  108  functions as a time-gate that closes progressively, initially at the exit port  106  and then continues sequentially in the downstream direction, to move excess fluid and foreign matter away from the exit port  106 . The seal  108 , seat  104  and retainer  110  interact to create a reusable compression seal. This provides a means for preventing migration of gas, liquid, or solid contaminants across the compression seal at the exit port  106  or opening in the seat  104 . The compression seal not only prevents the escape of fluid from the inside and entry of foreign from the outside, but it also provides a substantially impermeable seal for multiple reversible cycles of dispensing the fluid, by fastening and removing the cap  112 . 
     The seat  104  seals the interior, exterior and top surfaces of the neck of the container  102 . The material for the seat is chosen to be compatible with the material comprising the neck of the container. For example, if the neck of the container is plastic, one chooses a compatible plastic for the seat that enables a strong compression fit between the seat  104  and the neck of the container  105 . The threads  126  on the neck of the container  105  effect a compressive force to form the primary seal  132  between the seat  104  and the top of the container  102  as the seat  104  is threaded onto the neck of the container  105 . The threading action also effects a strong secondary seal between the seat  104  and the interior  120  and exterior  126  surfaces of the neck  105  of the container  102 . For additional protection, these threads can be designed as a one-way ratchet thereby providing a tamper-proof or tamper-evident benefit. For example, if the ratcheted threads  128  on the seat  104  are engaged by clockwise rotation with the ratchet projections  129  on the neck  105  of the container  102 , as shown in FIG. 4B, attempts to disengage the threaded parts by counterclockwise rotation may prove impossible without stripping the threads. The presence of stripped threads will provide evidence that someone has tampered with the delivery system. 
     The cap  112 , retainer  110 , seal  108  and seat  104  thus form a modular valve assembly that prevents the escape of fluid from inside and the entry of foreign matter into the system from the outside. By using a combination of snapping, press fitting or screwing operations, the four parts can be assembled and then easily integrated into a variety of containers. The modular valve assembly closure is designed to provide particular sealing benefits for containers that may have a relatively wide range of neck tolerances, such as those produced in bulk quantities or by co-blow molding operations. 
     FIG. 5 shows an alternate embodiment of a valve assembly. A retainer  110  includes an annular projecting surface  160  on its base for conformable snap engagement with a congruent annular projection  162  provided on the exterior surface of the neck of container  102 . In this embodiment, retainer  110  also includes a resilient spring like portion  164  that expands to enable snap engagement of the annular surface  160  of the container against annular projection  162  of the cap. Once the retainer is engaged on the cap, portion  164  applies a compressive force downward against the base  140  of seal  108  that seals the top surface  132  of the neck  105  of container  102  and shoulder portion  130  of seat  104 . 
     In accordance with an aspect of the invention, a container manufacturer or provider of a fluid material can attach the valve assembly to a container as the last step in a filling line. This allows for minimal or no filling line changes by the manufacturer. In addition, the valve assembly provides a maximum seal that can be used with blow molded containers or any product where manufacturing tolerances cannot be maintained within a tight range. The seal provided by the valve assembly is essentially airtight, shockproof, leakproof, evaporation proof and immune to variations in temperature and pressure. Therefore, the valve assembly enables ease of transport and long-term storage of fluids without contamination or changes in volume and concentration. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the enclosed embodiments, but on the contrary is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. For example, the retainer does not need to be threaded to the neck of a container. The retainer may be provided with a flexible portion for snap engagement with a rim on the neck of a container. Other appropriate anchoring mechanisms can be used. Therefore, persons of ordinary skill in this field are to understand that all such equivalent structures are to be included within the scope of the following claims.