Abstract:
A dispensing valve for fluids is disclosed which provides for ease of use by requiring only a minimal force exerted on the valve actuator to maintain the valve in an open position. A resilient valve actuator having the characteristics of a nonlinear spring is provided at an actuator end of the valve body and operatively connected to a plunger; with the opposite end of the plunger mounting a resilient valve seal that serves to pen and close a plurality of port openings. The valve may be manufactured with a variety of port configurations to provide for the dispensing of fluids of varying viscosities. The valve body and actuator are formed to allow the dispensing valve to be sterilized through high levels of radiation and through high temperature steam and chemical sterilization processes without degrading the valve structure or operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 09/827,549 filed Apr. 6, 2001 by the inventor herein and entitled “Dispensing Valve for Fluids”, now U.S. Pat. No. 6,491,189, which is based upon and gains priority from U.S. Provisional patent application Serial No. 60/195,232, filed Apr. 7, 2000 by the inventor herein and entitled “Dispensing Valve for Fluids,” and U.S. Provisional Patent Application Serial No. 60/204,326, filed May 15, 2000 by the inventor herein and entitled “Dispensing Valve for Fluids,” the specifications of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to fluid dispensing apparatus and, more particularly, to a robust, relatively simple, low-cost, and easily actuatable dispensing valve for dispensing fluid from a source of such fluid, which valve may withstand sterilization procedures including irradiation up to 5.0 MRAD and high temperature steam and chemical sterilization processes without degradation of the integrity of the valve structure or operation, and thus may be used for dispensing a wide variety of products ranging from aseptic products (free from microorganisms), to sterile products, to non-sterile products. 
     2. Description of the Background 
     Dispensing valves for dispensing fluid from fluid containers, systems, or other sources of such fluid are shown by U.S. Pat. Nos. 3,187,965; 3,263,875; 3,493,146; 3,620,425; 4,440,316; 4,687,123; and 5,918,779. Such valves can be used, for example, in a system for dispensing beverages or other liquids used by consumers in the home. Low cost, trouble-free, and reliable valve action are significant considerations in these applications. Low cost is particularly important if the valve is to be sold as a disposable item as, for example, where the valve is provided with a filled fluid container and discarded along with the container when the fluid has been consumed. 
     In U.S. Pat. No. 3,187,965, a dispensing valve for a milk container is shown having a generally integral valve body connected at one end to the milk container. The valve body has an L-shaped passage formed therein defining an inlet opening at one end in communication with the milk container and at the opposite end a discharge outlet for discharging the milk to the exterior of the container. A plunger bore in the valve body provides means for slidably mounting a plunger member. A valve seal fixedly connected to the inner end of the plunger member can be moved by the plunger member to open and close the inlet opening. The opposite or outer end of the plunger member extends to the exterior of the milk container. A push button having a diameter substantially larger than the plunger member is mounted to the outer end of the plunger member and disposed in the valve body so that the push button is exposed for engagement by a user&#39;s finger. A compression type spring is engaged between the push button and the valve body. Thus, when a force is exerted against the push button to move the valve seal and open the inlet opening for dispensing milk from the container, the spring at all time exerts a substantial counter force on the push button for returning the valve seal to a closed position. The force exerted by the compression spring tends to increase directly with the inward displacement of the plunger member. Therefore, the user must exert considerable inward force on the push button to hold the valve open. 
     Another valve, shown in U.S. Pat. No. 3,263,875, uses a similar plunger member and valve body to that of the &#39;965 patent. A resilient diaphragm having a peripheral portion engaged with the valve body acts both as a return spring and as a push button. Unfortunately, commercially available valves having such diaphragmatic actuator members have in the past required the user to exert considerable force to hold the valve open while dispensing the liquid. 
     Likewise, commercial attempts have been made to provide low-cost dispensing valves for use with disposable containers, but such efforts have met with limited success. For example, Waddington &amp; Duval Ltd. provide a press tap for use with disposable containers (such as wine boxes, water bottles, and liquid laundry detergent containers) under model designations COM 4452 and COM 4458, both of which provide a depressible button actuator operatively connected to a valve closure for moving the valve closure away from a valve seat to dispense fluid. Unfortunately, the valve constructions are configured such that fluid to be dispensed will rest within the dispensing chamber of the valve behind the valve seat after use and thereby outside of any refrigerated or insulated container in which the liquid is stored, thus increasing the risk of spoilage of the volume of fluid resting within the valve body after each use. Moreover, many fluid dispensing applications require vigorous sterilization procedures prior to use of the dispensing equipment, including irradiation at exposures of up to as high as 5.0 MRAD, and high temperature steam and chemical sterilization procedures. The thin-walled polyethylene construction of the valve bodies of the Waddington &amp; Duval dispensing valves cannot withstand such sterilization procedures, and in fact become brittle and prone to failure when exposed to such procedures, thus greatly limiting their use for dispensing food products. Even further, the polyethylene valve closure of the Waddington &amp; Duval dispensing valve construction is highly thermally conductive, such that heat transfer may easily occur between the exterior of the fluid container and the contents of the container simply through the valve structure, again raising the risk of spoilage of the contents. 
     Similarly, the Jefferson Smurfit Group provides a similar tap for use with disposable containers under the model designation VITOP. Once again, the Jefferson Smurfit Group tap construction is configured such that fluid to be dispensed will rest within the dispensing chamber of the valve behind the valve seat after use and thereby outside of any refrigerated or insulated container in which the liquid is stored, once again increasing the risk of spoilage of the volume of fluid resting within the valve body after each use. Likewise, the thin-walled polypropylene construction of the valve body of the Jefferson Smurfit Group dispensing valve cannot withstand the above-described sterilization procedures, and also becomes brittle and prone to failure when exposed to such procedures, thus greatly limiting their use for dispensing food products. And, as above, the polyester elastomer closure of the Jefferson Smurfit Group dispensing valve construction is highly thermally conductive, such that heat transfer may easily occur between the exterior of the fluid container and the contents of the container simply through the valve structure, again raising the risk of spoilage of the contents. 
     Thus, although substantial effort has been devoted in the art heretofore towards development of low-cost valves of this general type, there remains an unmet need for a valve which is easier to use and which does not require that the user exert such large forces to hold the valve open. This problem is complicated by the fact that the spring or other resilient member should provide the force necessary to assure leak-free seating of the valve seal when the plunger member is in the closed position. Likewise, there remains an unmet need for a disposable valve, which is sufficiently robust so as to be able to withstand vigorous sterilization procedures, which reduces heat transfer through the valve between the interior and exterior of the fluid container, and which does not trap fluid outside of the intended storage vessel between dispensing cycles. 
     Moreover, for a dispensing valve provided as a component of a throwaway fluid container, it would be highly advantageous to provide an easy to use dispensing valve, which offers the user assurance that the valve has not previously been used or tampered with, and that the integrity of the contents of the fluid container has not been compromised. Unfortunately, the need for such a feature has not been met by prior art dispensing valves. 
     There is further need for a valve that can be adapted, during manufacture, to provide the desired liquid flow rate for a particular set of conditions such as liquid viscosity and the liquid pressure or “head” available to force the liquid through the valve body. A valve that discharges a thick, high-viscosity fluid such as cold maple syrup or orange juice concentrate at a desirable rate will discharge a low-viscosity fluid such as water or wine under the same pressure at a far higher rate. It would be desirable to provide a valve, which can be fabricated readily using normal production techniques such as injection molding in a range of configurations, having different resistance to fluid flow, to provide for these different conditions. It would be particularly desirable to provide a valve, which can be fabricated in these different configurations while with only minor modifications to the molds, and other tools used to make the valve. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a fluid dispensing valve which avoids the disadvantages of the prior art. 
     It is another object of the present invention to provide a fluid dispensing valve that requires minimal force to maintain the valve in an open position while providing leak-free closure of the valve when seated in a closed position. 
     It is yet another object of the present invention to provide a fluid dispensing valve that may be manufactured in a variety of configurations to allow effective application to fluids of varying viscosities with only minor modifications to manufacturing equipment used to make the valve. 
     It is even yet another object of the instant invention to provide a fluid dispensing valve that provides a user a means of determining whether or not the valve has previously been actuated and possibly compromised the integrity of the fluid to be dispensed. 
     It is still even yet another object of the instant invention to provide a fluid dispensing valve that is of sufficiently robust construction so as to withstand sterilization procedures including exposure to high levels of radiation and high temperature steam and chemical sterilization without degrading the performance or integrity of the valve structure. 
     It is still yet another object of the instant invention to provide a fluid dispensing valve that reduces heat transfer from the exterior of a liquid container to which the valve is attached to the interior of the container. 
     It is still even yet another object of the instant invention to provide a fluid dispensing valve that prevents the storage of fluid behind the valve closure and outside of the fluid container after each dispensing cycle. 
     In accordance with the above objects, a dispensing valve for fluids is disclosed which provides for ease of use by requiring only a minimal force exerted on the valve actuator to maintain the valve in an open position, and which offers a simple, ergonomic design and robust functionality capable of dispensing a wide variety of products. In a first embodiment, the valve body and actuator are formed of a polypropylene copolymer with an average wall thickness of approximately 0.0625 inches, and the valve seal is formed of a thermoplastic rubber having an average thickness of about 0.032 inches. Such dimensional characteristics and materials allow the dispensing valve to withstand the highest aseptic sterilization regimentation as outlined by the Food &amp; Drug Administration (FDA) and maintain the sterility of a product as specified by the National Sanitation Foundation (NSF) guidelines. More specifically, the dispensing apparatus is able to withstand either gamma or cobalt irradiation at the maximum dose of 5.0 MRAD (50 Kilogray) in the first phase of the sterilization process. The dispensing apparatus is then able to withstand the high temperatures associated with the steam and chemical sterilization processes required in the filling process. The dispensing apparatus is capable of withstanding these combined sterilization regimens without degrading the valve structure or operation. Thus, the valve of the instant invention may be used to dispense products ranging from aseptic products (free from microorganisms) including but not limited to dairy, 100% juice and soy products, to commercially sterile products including but not limited to preserved juice and coffee products, to non-sterile fluids such as chemical solvents. 
     In order to allow a minimal force for holding the valve in an open position, a resilient valve actuator having the characteristics of a nonlinear spring is provided at an actuator end of the valve body and operatively connected to a plunger, with the opposite end of the plunger having mounted thereon a resilient valve seal. An intermediate discharge outlet is positioned between the actuator end and the valve seal, such discharge outlet being placed in fluid communication with the interior of a fluid container to which the valve is attached when the valve is in an open position. A valve port wall is positioned between the valve seal and the dispensing chamber providing a plurality of ports for controlling the flow of fluid through the valve body when the valve is in an open position. The valve and the valve port wall are positioned such that when the valve is installed on a liquid container, virtually no liquid will be trapped by the valve structure outside of the insulated container, thus preventing the spoilage of a dose of liquid resting in the valve after each dispensing cycle. A push-button is provided for actuating the dispensing valve and is exposed to the exterior of a fluid container to which the dispensing valve is attached. In one embodiment of the instant invention, the push-button is concentrically mounted within a breakaway circular rim. Upon first using the dispensing valve, a user depresses the push-button, dislodging the circular rim from the button, and thereby providing evidence that the valve had been opened, thus providing a tamper-evident actuator. The valve may be manufactured with a variety of port configurations to provide for the dispensing of fluids of varying viscosities. 
     The simplicity and functionality of the dispensing valve of the instant invention enables its manufacture and automatic assembly with high cavity tools, which in turn reduces manufacturing costs and offers the market a low cost dispensing solution. The simplicity and functionality of the design also enables the dispensing apparatus to be easily customized in the manufacturing process to fit a wide range of dispensing packages such as a flexible pouch, flexible bag, or semi-rigid plastic container. The dispensing valve of the instant invention is also configured to adapt easily to a wide range of filling machines and filling conditions worldwide. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment and certain modifications thereof when taken together with the accompanying drawings in which: 
     FIG. 1 shows a fluid container having a dispensing valve thereon in accordance with one embodiment of the present invention for the manual dispensing of fluid from the container. 
     FIG. 2 is an enlarged perspective view of the dispensing valve shown in FIG.  1 . 
     FIG. 3 is an end view of the actuation end of the dispensing valve body shown in FIGS. 1 and 2. 
     FIG. 4 is a view of the inlet end of the dispensing valve body shown in FIGS. 1 and 2. 
     FIG. 5 is an enlarged cross-section of the dispensing valve shown in FIG. 2 with an added tamper evident feature. 
     FIG. 5 a  is an enlarged cross-section of the dispensing valve shown in FIG. 2 without an added tamper evident feature. 
     FIG. 6 is an exploded view of certain components for the dispensing valve shown in FIGS. 1-5. 
     FIG. 7 is an elevational view of the valve seal shown in FIGS. 5 and 6. 
     FIG. 8 a  is a graph illustrating certain forces acting during the operation of the valve of FIGS. 1-7 wherein the actuator is formed of a polypropylene copolymer. 
     FIG. 8 b  is a graph illustrating certain forces acting during the operation of the valve of FIGS. 1-7 wherein the actuator is formed of polyethylene terephthalate. 
     FIG. 9 is a view similar to FIG. 4 but depicting a valve body in accordance with a further embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings FIG. 1 shows a container or vat  10  having a juice or other fluid disposed therein. A dispensing valve  12  in accordance with one embodiment of the present invention is connected for dispensing the fluid in container  10 . While the dispensing valve  12  is shown for dispensing the fluid under gravity flow, those skilled in the art will readily recognize that this is merely for purposes of illustration and not by way of limitation. Dispensing valve  12  is also applicable for dispensing fluid where the source of fluid is under a head of pressure provided by a source other than gravity. 
     As is further shown in FIGS. 2 to  7  of the drawings, dispensing valve  12  has a generally tubular valve body  13  having an outer wall  13   a  and an inner wall  13   b . The valve body has an inner or inlet end  7 , and an opposite outer or actuation end  9 , and an axial direction extending between these ends. Although the valve body is shown generally in the form of a round cylindrical tube, the valve body may be round, square, octagonal or other shape adapted for the application to which the dispensing valve  12  will be applied. Valve body  13  is provided with features  14  for connecting the valve body to the container  10  or other source of fluid to be dispensed so as to bring the inlet opening  15  (FIG. 5) formed in the valve body  13  in communication with the fluid to be dispensed. The particular connecting features  14  depicted in the drawings include ribs encircling the exterior of the valve body near the inlet end  7 . These ribs are arranged to form a fluid-tight, press-fit connection between the exterior of the valve body and the interior of an outlet provided in the container. Other suitable connecting and sealing features may be used in addition to or in lieu of the ribs. For example, the valve body can be provided with threads or bayonet-type locking features matable with features of the container. In addition, auxiliary sealing elements such as resilient O-rings or other gaskets can be provided on the container or on the valve body for engagement between the valve body and the container. 
     A discharge outlet  16  is formed in the valve body at a location on the valve body between the inlet end  7  and actuator end  9 . Outlet  16  is disposed outside of the container or other source of fluid when the valve body is engaged with the container. The discharge outlet  16  is generally in the form of a short tubular member extending in the direction perpendicular to the axial direction of the valve body and communicating with the interior of the valve body. 
     Further, a positioning ring  14   a  is provided circumscribing the valve body just above connecting features  14 . When the dispensing valve of the instant invention is installed on a fluid container, positioning ring  14   a  abuts the exterior wall of the container. As will be discussed in greater detail below, a discharge outlet  16  extends from a port wall on the interior of the valve body, which port wall is ordinarily closed with a valve seal. In its closed position (seated against the port wall), the valve seal is positioned a short axial distance from positioning ring  14   a , preferably not more than about 0.25 inches, so as to limit the amount of fluid contained within the portion of the valve outside of the fluid container to the volume within the inlet end of the valve between positioning ring  14   a  and the valve seal. By limiting the amount of fluid that may be contained within the valve structure after a dispensing cycle, the risk of subjecting a dose of liquid held within the valve after a dispensing cycle to temperature fluctuations is reduced, in turn reducing the risk of dispensing a dose of spoiled liquid at the start of the following dispensing cycle. 
     As shown more particularly in FIGS. 4 and 5, valve port wall  17  extends across the interior of body  13  between inlet opening  15  and discharge outlet  16 . The valve port wall defines a set of holes or valve ports  17   a , as well as a valve seat  18  encircling the valve ports  17   a  and facing toward the inlet opening  15 . The valve port wall also defines a plunger guide opening  17   b  adjacent the central axis of the valve body. As best seen in FIG. 5, a plunger guide support wall  5  extends across the valve body just outward of discharge opening  16 , so that the plunger guide support wall  5  lies between the discharge opening and the actuator end of the valve body. A tubular plunger guide  20  extends outwardly from the plunger guide support wall, toward the actuator end  9  of the valve body. The plunger guide  20  is aligned with the plunger guide opening  17   b  of the valve port wall. The valve body also has a pair of grip wings  30  and  31  projecting outwardly from the remainder of the valve body at actuator end  9 . Grip wings  30  and  31  extend generally in directions perpendicular to the axial direction of the valve body and perpendicular to the direction of discharge opening  16 . Valve body  13  desirably is formed from a polymeric material compatible with the fluid to be dispensed as, for example, a thermoplastic such as polypropylene or other polyolefin. In a preferred embodiment, valve body  13  is formed from a polypropylene copolymer. 
     A plunger member  21  is slidably mounted in plunger guide  20 . Plunger member  21  desirably is also made of polypropylene or other plastic material. In a preferred embodiment, plunger member  21  is likewise formed from a polypropylene copolymer. Plunger member  21  has an inner end  22  that extends through the plunger guide support wall  5 , through discharge outlet  16  and through the plunger guide opening  17   b  of valve port wall  17  into the inlet opening  15 . 
     A resilient valve seal  19  in the form of a shallow conical member is fixedly connected to the inner end  22  of the plunger member, as by a coupling element  22   a  which can be force fitted into engagement with a sized opening  19   a  in the valve seal  19  because of the resilient nature of the materials from which the valve seal  19  and plunger  21  are fabricated. Valve seal  19  can be formed from essentially any resilient material, which will not react with or contaminate the fluid being dispensed, and which will not melt or degrade under the conditions encountered in service. For example, a thermoplastic or thermosetting elastomer or other flexible material, typically in the range of about 30 to about 80 Shore A durometer, and more preferably, about 50 to about 80 Shore A durometer, can be employed in typical beverage dispensing applications. In a preferred embodiment, valve seal  19  is formed from a thermoplastic rubber. The periphery of valve seal  19  overlies valve seat  18  and seals against the valve seat when the valve is in the closed position depicted in FIG.  5 . 
     The thickness of the valve seal will depend on the material and operating conditions. Merely by way of example, in a valve for dispensing beverages under gravity head (e.g., on the order of 0.5 to 1 pound per square inch pressure), the valve seal is about 1 inch in diameter and about 0.020 to 0.040 inches thick, most preferably about 0.032 inches thick, at its periphery. 
     A cylindrical stop member  28  and actuator  24  are formed integrally with the plunger member  21  at the outer end  23  of plunger member  21  remote from the inner end  22 . Actuator  24  has a dome-shaped resilient section  25 , so sized that the perimeter  26  of this dome-shaped section can be mounted or held from escaping by a ledge or groove  27  disposed on the inner wall  13   b  of the valve  13 , just inward of the actuator end of the valve body  13 . The dimensions of the actuator are selected to provide the desired resilient action and force/deflection characteristics as discussed below. In one exemplary embodiment, the plunger, stop member, and actuator including resilient element  25  are molded as a unit from polypropylene. The resilient element  25  is generally conical and about 1 inch in diameter, with an included angle of about 160°. That is, the wall of the conical resilient section lies at an angle A (FIG. 6) of 10° to the plane perpendicular to the axial direction of the plunger member. The resilient element  25  is about 0.012 inches thick at its perimeter, and about 0.018 inches thick at its juncture with stop member  28 . Stop member  28  is about 0.292 inches in diameter. Thus, the ratio between the axial extent x of the conical resilient section and the average thickness of the resilient section is about 4. 
     Stop member  28  coacts with a stop shoulder  29  formed by the outer end of the plunger guide  20 . Thus, the distance that the plunger  21  can be moved when force is exerted on the plunger member at actuator  24  will be determined by the distance the stop member  28  can travel before contact is made with the stop shoulder  29 . 
     In operation, the valve is mounted to the container as shown in FIG.  1 . The discharge opening points downwardly outside of the container, whereas finger grip wings  30  and  31  project horizontally. The valve normally remains in the fully closed position depicted in FIG.  5 . In this position, the resilience of actuator  24  urges the plunger  18  outwardly, toward the actuator end  9  of the housing, and holds the valve seal  19  in engagement with seat  18 , so that the head blocks flow from the inlet opening  15  to ports  17   a  and discharge opening  16 . In this condition, the pressure of the liquid  11  in the container tends to force the head against seat  18 , thereby closing the valve tighter. Those portions  17   c  of the valve port wall  17  immediately surrounding the ports  17   a  support the valve seal and prevent it from buckling through into discharge opening  16 . This helps to assure that the seal will not be broken in the event very large fluid pressures are applied, as may occur, for example, if container  10  is shaken or dropped. Stated another way, head  19  can be so soft and flexible that if support portions  17   c  of the valve port wall were absent, the head would be susceptible to such buckling. This ability to use a soft flexible head without fear of leakage under extreme conditions in turn facilitates formation of an effective seal at seat  18 . The valve port wall also provides an additional guide for plunger  21 , which facilitates sliding movement of the plunger, reduces any tendency of the plunger to bind, and keeps head  19  concentric with seat  18 . 
     The user can open the valve by grasping the finger grip wings  30  and  31  with his or her fingers and pressing his or her thumb against the center section of the button  61  so as to intentionally move actuator  24 , plunger member  21 , and valve seal  19  in an opening direction aligned with the central axis of the valve body and transverse to valve port wall  17 . Such movement takes the plunger member and valve seal from the normally closed position towards an open position, in which stop member  28  on the plunger engages stop wall  29  on the plunger bore of the valve body. In this open position, the valve seal is remote from valve port wall  17  and remote from seat  18 , so that the valve seal does not occlude ports  17   a  and hence fluid can flow from container  10  to discharge opening  16 . 
     As the user forces the plunger inwardly towards the open position, the resilient element  25  is deformed. The closing or outward force applied by the resilient element  25  may rise as the plunger is displaced. However, the closing force does not increase linearly with inward displacement toward the open position. As schematically shown in graphical form in FIG. 8 a , the closing force curve  46  for the valve as described above first rises with opening displacement from the closed position  40   a , but then the increase in closing force per unit opening displacement declines until the plunger member and valve seal reaches a point of maximum closing force at an intermediate position  42   a , at which point the outward or closing force begins to decline with increasing opening displacement. The valve preferably exhibits a maximum closing force of 2 to 2.5 pounds at intermediate position  42   a . The outward or closing force exerted by the resilient section  25  then decreases further with further opening displacement. However, the plunger reaches the full open position  44   a , where stop member  28  engages stop wall  29  (FIG. 5) and arrests opening displacement before the outward or closing force declines to zero. At such full open position  44   a , the valve preferably requires a holding force of only 0.75 pounds. Stated another way, the dome-shaped or conical resilient section  25  provides a nonlinear spring characteristic with rising and falling force sections. The travel distance set by stop member  28  and stop wall  29  is selected so that the full open position lies on the falling force section of the characteristic curve, with an opening force less than the maximum achieved during travel. In the exemplary embodiment discussed above, the total travel from full closed position to full open position is from about 0.25 inches to 0.75 inches. 
     In a first alternate embodiment depicted by force curve  47   a , resilient element  25  is provided with a greater average thickness of approximately 0.0155 inches, in turn requiring a larger closing force of approximately 3-3.5 pounds at intermediate position  42   a ′, and thereafter exhibiting a declining closing force until reaching a minimum of approximately 0.75 pounds to hold the valve in an open position. Such an increased intermediate closing force has been shown to provide a greater snap-type closure effect upon releasing the valve from the full open position, thus reducing the risk of inadvertent operation of the valve. 
     In a second alternate embodiment depicted by force curve  46   b  of FIG. 8 b , resilient element  25  is formed from polyethylene terephthalate (PET-C) and dimensioned as discussed above with an average thickness of 0.015 inches. Such a construction for resilient element  25  requires an even larger closing force of approximately 4-4.5 pounds at intermediate position  42   b , and thereafter exhibiting a declining closing force until once again reaching a minimum of approximately 0.75 pounds to hold the valve in an open position. 
     Still further, in yet a third alternate embodiment depicted by force curve  47   b  of FIG. 8 b , resilient element  25  is again formed from PET-C and dimensioned with an average thickness of 0.0155 inches, in turn requiring an even larger closing force of approximately 5-5.5 pounds at intermediate position  42   b ′, and thereafter exhibiting a declining closing force until once again reaching a minimum of approximately 0.75 pounds to hold the valve in an open position. 
     Thus, by using alternate polymers and thicknesses of actuator  24 , the force versus displacement curve may be modified as shown in the various force curves of FIGS. 8 a  and  8   b  so that during inward displacement from full closed position  40  to full open position  44 , intermediate positions  42  exhibit greater closing forces, thus increasing the snap-type closure effect upon release of the valve actuator. 
     Furthermore, by constructing each of the valve elements as discussed above, namely, forming the valve body from a polypropylene copolymer having a minimum average wall thickness of 0.0625 inches, and forming the valve seal from a thermoplastic rubber having an average thickness of about 0.032 inches, the valve structure may be subjected to the vigorous sterilization processes necessary for using the valve in food applications, including irradiating the structure at up to 5.0 MRAD and subjecting the structure to high temperature chemical and steam sterilization processes, without causing the valve structure to become brittle or otherwise jeopardizing the integrity of the valve&#39;s structure or operation. 
     The non-linear spring characteristic provides several significant advantages. It can provide a substantial closing force at the full closed position, and hence an effective seal, with a low holding force at the full open position. The user can keep the valve open while the liquid is flowing with only moderate effort. The highest actuating forces are encountered only briefly, during travel from the closed position to the open position, and do not tend to cause fatigue. By contrast, in a valve with a conventional linear spring, the highest closing forces are encountered at the full open position, so that the user must continually resist such high forces while the liquid is flowing. Further, the nonlinear spring action provides a desirable “feel” or tactile feedback, which confirms to the user that the valve is open even if the user cannot see the flow or is not looking at the flow. 
     Because the finger-gripping members  30  and  31  extend generally transverse to the discharge outlet  16 , and extend generally horizontally during use of the valve, the user&#39;s fingers will be supported above the bottom end of the discharge opening, out of the stream of fluid discharged from the opening. Thus, if a hot fluid is being dispensed, it will not harm the user. 
     In the embodiment of the instant invention shown in FIG. 5, a separate push button element  60  is provided for manual engagement by a user to operate the dispensing valve. Push button  60  is preferably formed as a disk having a generally planar top surface  61  and a bottom surface  62  on the opposite side from the top surface  61 . Extending downward from and centrally located on bottom surface  62  is an engagement pin  63 . In the embodiment of the instant invention depicted in FIG. 5, the dome-shaped resilient section  25  of actuator  24  is provided with a central opening  64  sized to receive engagement pin  63  therein and to hold the same in place via a friction fit. Thus, depressing push button element  60  downward and into tubular volume body  13  likewise causes plunger member  21  and valve seal  19  to move in an opening direction aligned with the central axis of the valve body and transverse to valve port wall  17 , precisely as described above. Preferably, engagement pin  63  is provided a circumferential ring  63   a  positioned around pin  63  adjacent to the point at which pin  63  attaches to bottom surface  62 . Ring  63   a  defines a ledge  63   b  generally parallel to bottom surface  62 . When inserted into actuator  24 , pin  63  thus fits snugly within central opening  64  in actuator  24 , while ledge  63   b  lies flush against the top face of actuator  24 . Thus, when push button element  60  is pushed downward, only ledge  63   b  comes in contact with actuator  24 , thus ensuring that the dome-shaped resilient section does not lose its shape or its nonlinear spring characteristic when the button is actuated. 
     In an alternate embodiment of the instant invention, push button element  60  further comprises a detachable tamper indicating ring  70  circumscribing push button element  60 . Tamper indicating ring  70  is defined by an outer vertical wall  71 , a top wall  72 , and a short inner vertical wall  73  of smaller vertical dimension than outer wall  71 . Outer vertical wall  71  has a thickness  71   a  such that the bottom of outer vertical wall  71  defines a flat surface sized to seat against the actuation end  9  of tubular valve body  13  surrounding actuator  24 . Inner vertical wall  73  is provided with a plurality of tabs  74  extending towards the interior of tamper indicating ring  7 , each tab  74  having a narrow terminal section  75  at its bottom end, which terminal sections  75  are attached to the upper and outer edge of push button element  60 . Tabs  74  are preferably configured so as to position push button element  60  substantially below the plane defined by the uppermost extent of top wall  72 , such that when push button element  60  is assembled with actuator  24  within the dispensing valve  12 , the outermost point of the actuation end  9  is top wall  72 . Thus, by recessing push button  60  into the structure of dispensing valve  12  and below top wall  72 , inadvertent or accidental actuation of the valve (through bumping against a surface, etc.) may be averted. 
     In use, a new dispensing valve  12  is provided on an unused container with push button element  60  installed in actuator  24  with tamper indicating ring  70  intact. Upon the first actuation of the valve through depression of push button  60 , movement of tamper indicating ring  70  is blocked by the upper edge of tubular valve body  13 , such that movement of push button element  60  into valve body  13  results in tamper indicating ring  70  separating from push button element  60  and falling away from dispensing valve  12 . Thus, previous actuation of valve  12  may be readily apparent to a user based upon either the presence or absence of tamper indicating ring  70  from push button element  60 . 
     The fluid flow resistance of the valve in the open position is controlled in large measure by the flow resistance of ports  17   a . Thus, the fluid flow resistance of the valve can be selected to fit the application by selecting the number and size of the ports. The number and size of ports  17   a  can be varied through only slight modification of injection molding apparatus (such as by varying movable pin positions within such a mold structure). This allows the manufacturer to make valves for almost any application with only insignificant tooling costs. Ports  17   a  need not be round; other shapes, including arcuate ports  17   a ′ (FIG. 9) extending partially around the center of the valve body and partially around plunger guide opening  17   b ′, can be made with appropriate interchangeable injection molding components. 
     Since the dispensing valve  12  as above described is made with only a few parts formed by conventional, simple molding techniques, it is relatively simple in operation and cheap to manufacture. It is inherently reliable, and does not require extreme precision in manufacture. 
     Those skilled in the art of spring design will readily recognize that other shapes for the resilient element  25  of the actuator, such as rectangular, cruciform, and octagonal can also be used without departing from the scope of the present invention. In addition, as discussed above, the resilient element  25  may be disposed at the exposed or actuator end of the plunger, so that the resilient section acts as part of the push button and closes the actuator end of the housing. However, this is not essential, and the resilient element can be disposed within the valve body, at a location inaccessible to the user, as explained in detail above through use of push button element  60 . Additionally, although it is highly advantageous to form the resilient element integrally with the plunger member, this is not essential. Conversely, the valve seal  19  can be formed integrally with the plunger member, rather than assembled to the plunger member as discussed above, with the resilient element attached afterwards. Furthermore, the resilient element may optionally be formed from plastic or metal. 
     Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein.