Abstract:
Liquid dispenser for dispensing a carbonated liquid from a container, the liquid dispenser including a compartment, a container sealing region, a compartment sealing region, and a valve, the compartment extending upwardly from a neck portion of the container, the neck portion and the compartment defining an opening to the atmosphere between the compartment and the neck portion, the container sealing region being located between the neck portion and the opening, the compartment sealing region being located between the compartment and the opening, the valve being movable within the compartment, from a closed position pressed toward the neck portion, to an open position away from the neck portion, the valve including a first surface facing the compartment, a second surface facing the opening, a first valve sealing region, a second valve sealing region, and a channel extending from the neck portion to the compartment, the first valve sealing region matching the container sealing region, for preventing passage of fluids between the neck portion and the opening, when the valve is in the closed position, the second valve sealing region matching the compartment sealing region, for preventing passage of fluids between the compartment and the opening, when the valve is in the closed position, the channel enabling passage of fluid from the neck portion to the compartment.

Description:
FIELD OF THE DISCLOSED TECHNIQUE 
     The disclosed technique relates to liquid dispensers in general, and to methods and systems for dispensing a carbonated beverage from a container, in particular. 
     BACKGROUND OF THE DISCLOSED TECHNIQUE 
     When the cap of a container of a carbonated beverage, such as plain soda water, soda water with additives, beer, and the like, is removed from the container, the gas tends to escape from the container, thereby causing the original taste of the carbonated beverage to deteriorate. Thus, it is desirable to prevent the escape of the gas from the container, when the container is not being used. 
     Methods and systems for preventing the gas to escape the container, are known in the art. These systems generally employ a valve of some kind, which normally seals the mouth of the container and when actuated by a user, the valve opens the mouth of the container to the atmosphere, thereby allowing the user to dispense the liquid from the container, under the pressure of the gas. 
     U.S. Pat. No. 5,918,779 issued to Ventura and entitled “Valve Assembly for Supplying Pressurized Liquid From a Container”, is directed to a valve assembly for dispensing pressurized liquid from a Polyethylene Terepthalate (PET) bottle. The valve assembly includes a body, a valve member and a dip tube. The body includes a transverse partition wall, an axial conduit, a supplying orifice, a supplying spout, a top opening, a dome-cap and a tube-retaining socket. The valve member includes a membrane-like disc, a plurality of resilient arms, a closing piece and an actuating stem. The dome-cap includes a dome and an actuating projection. 
     The transverse wall is conical. The dome-cap is coupled with the top opening. The axial conduit is located at the center of the body and communicates with the supplying orifice. The supplying orifice communicates with the supplying spout. The tube-retaining socket is coupled to the lower portion of the body. The membrane-like disc is located between the tube-retaining socket and the transverse partition wall. The dip tube is coupled with the tube-retaining socket and enters into the PET bottle, to communicate with the liquid. 
     The closing piece is located on top of the resilient arms and the actuating stem is coupled with the top portion of the closing piece. The actuating stem is located below the actuating projection. The user pushes the dome-cap down, wherein the actuating projection makes contact with the actuating stem and moves the closing piece down against the resilient arms. The liquid flows up through the dip tube, a valve opening generated between the closing piece and the transverse partition wall, through the axial conduit, the supplying orifice and out through the supplying spout. 
     U.S. Pat. No. 5,390,832 issued to Lombardo and entitled “Apparatus for Dispensing a Pressurized Liquid”, is directed to an apparatus for dispensing a pressurized liquid from a container. The apparatus includes a head member, a valve member, a liner, a shaft, a cover, a locking ring, a locking pin and a knob. The head member includes a bottle attachment cylinder, a siphon tube, a flow passage, a conical valve chamber and a pour spout. The bottle attachment cylinder includes internal threads for screwing the apparatus on a bottle. The siphon tube is coupled with the flow passage and the siphon tube enters into the bottle to be immersed into the liquid. The flow passage is located between the siphon tube and the apex of the conical valve chamber. The pour spout is coupled with the wide portion of the conical valve chamber. 
     The valve member is conical and fits within the conical valve chamber. The liner includes a converging portion which is located between the valve member and the inner surface of the conical valve chamber and a diverging portion. The cover includes internal threads for being screwed on an end of the head member. An end of the diverging portion is clamped between the end of the head member and the cover, to seal the space between the conical valve chamber, the flow passage and the pour spout. 
     The shaft includes an enlarged diameter segment and a smaller diameter segment. The enlarged diameter segment is externally threaded, in order to be screwed into a threaded bore of the valve member. The smaller diameter portion of the shaft passes through the cover and is fastened to the knob, by the locking pin. The locking ring is located between the cover and the knob, to prevent axial movement of the shaft. Since the liner restricts rotation of the valve member, rotation of the knob causes the valve member to move axially within the conical valve chamber, thereby allowing the liquid to flow from the siphon tube, through the flow passage and the conical valve chamber, out through the pour spout. 
     U.S. Pat. No. 5,350,090 issued to McClure and entitled “Beverage Dispenser”, is directed to a dispenser for dispensing a pressurized liquid from a container. The dispenser includes a head, a valve body, a trigger handle, a tube, a tube seal and an outlet. The lower portion of the head includes internal threads to be screwed onto a neck of a bottle. When the head is assembled on the bottle, the tube seal seals between the neck of the bottle, the head and the tube. The tube extends from the neck to the bottom of the bottle. The trigger handle is coupled with the valve body and the valve body is located on the top of the tube. When the trigger handle is pressed, the valve body allows the liquid to flow from the tube and through the valve body, out through the outlet. 
     U.S. Pat. No. 5,299,718 issued to Shwery and entitled “Bottle Closures”, is directed to a bottle closure to temporarily prevent a pressurized beverage to escape from a bottle. The closure includes a one-piece molded housing, a one-piece molded valve stem, a one-piece molded resilient push top, a circular underside and a spout. The one-piece molded housing includes an internal thread to be screwed on a top portion of a bottle. The valve stem includes a ball at one end thereof and a frusto-conical sealing skirt at another end thereof. The frusto-conical sealing skirt includes a rigid sealing skirt and a flexible sealing skirt. The circular underside includes rigid frusto-conical seat for mating with the rigid sealing skirt and with the flexible sealing skirt. The one-piece molded resilient push top includes a dome-type portion and a cylindrical extension. The cylindrical extension includes a socket for engaging with the ball of the valve stem. 
     Normally, the one-piece molded resilient push top pulls the valve stem up against the circular underside, such that the frusto-conical sealing skirt seals the rigid frusto-conical seat, thereby preventing the beverage to escape. When the user pushes the one-piece resilient push top down, the frusto-conical sealing skirt loses contact with the rigid frusto-conical seat and allows the beverage to flow out through the spout. 
     U.S. Pat. No. 4,804,116 issued to Ball and entitled “Valve for Dispensing Fluid From a Container”, is directed to a valve to dispense a liquid from a container, under a gas pressure. The valve includes a screw cap, a hollow grommet and a hollow valve rod. The screw cap includes internal threads for the valve to be screwed onto a neck of the container. The screw cap includes an aperture to hold the hollow grommet. The hollow grommet includes a skirt which fits on a dip tube. The dip tube enters the bottle to seek the low level of the liquid in the container. The hollow valve rod includes a flange. The hollow grommet is located within the screw cap and the hollow valve rod is located within the hollow grommet. The cap screw includes an annular passageway and a pipe union. The pipe union is coupled with a pressurized gas source. 
     Normally, the hollow grommet forces the flange against itself, thereby preventing the liquid to escape from the container. When the hollow valve rod is tilted sideways, a path for the liquid and a path for the pressurized gas to flow from the pressurized gas source through the annular passageway to the container is formed, thereby causing the liquid to flow out of the container under gas pressure. 
     U.S. Pat. No. 4,930,689 issued to Stumpf and entitled “Resealable Cap for a Container”, is directed to a cap for a container for allowing a carbonated liquid to flow out of the container, by pushing a button. The cap includes a body member, a spout, a button, a ventilation tube, an insert tube, two sealing members, a plunger, a compression spring, a retaining washer and a guide cylinder. The cap includes internal threads to be screwed onto a neck of the container. The guide cylinder is located at the bottom portion of the insert tube. The guide cylinder includes a plurality of projections. The insert tube is located within the cap and when the cap is screwed onto the container, the insert tube locates within the neck of the container and one of the sealing members seals between the insert tube and the neck. 
     The button is located at one end of the plunger and the other sealing member is located at the other end of the plunger. The plunger is located within the insert tube, such that the button locates on top of the cap and the sealing member seals the rim of the insert tube. The retaining washer is located at the lower portion of the plunger and the compression spring is located between the retaining washer and the projections of the guide cylinder, thereby forcing the sealing member to seal the rim of the guide cylinder. The button is pushed against the force of the compression spring, thereby unsealing the rim of the guide cylinder and opening a path for the carbonated liquid to flow out of the container through the spout. Meanwhile, air enters the container through the ventilation tube, thereby facilitating the flow of the carbonated liquid. 
     U.S. Pat. No. 5,924,606 issued to Huizing and entitled “Pouring Spout with Refill Prevention Device”, is directed to a pouring spout which allows pouring of a liquid from a bottle and prevents refilling of the bottle. The pouring spout includes a neck part, a closing part and a pouring spout housing. The pouring spout housing includes an upper part, a lower part, a cylinder member and a movable weight. The upper part includes a conical surface which diverges toward the lower part. The lower part includes a cylindrical part at the lower portion thereof. The cylindrical part includes a plurality of casing openings. The cylinder member is located within the cylindrical part and can move there within. The movable weight is located between the cylinder member and the conical surface. 
     The pouring spout is assembled on a neck of the bottle, such that the upper part, the lower part, the cylinder member and the movable weight are located between the neck of the bottle and the closing part. The neck part includes a lower groove and an upper groove. The lower groove mates with a groove on the periphery of the neck of the bottle and the upper groove mates with another groove on the periphery of the upper part. Thus, the neck part together with the upper part, the lower part, the cylinder member and the movable weight are coupled with the neck of the bottle and can not be removed without damaging the pouring spout. The closing part is coupled with the neck part by a breakable element. After breaking the breakable element, the closing part can be screwed onto the neck part. 
     When the bottle is located in an upright position, the movable weight forces the cylinder member toward the cylindrical part, thereby closing the casing openings. When the bottle is tilted at an angle which exceeds the angle of the conical surface, the movable weight and the cylinder member move toward the upper part, the casing openings open and the liquid pours out of the bottle. 
     U.S. Pat. No. 5,680,970 issued to Smith et al., and entitled “Self Closing Dispensing Valve Biased by Resilient Fingers”, is directed to a dispensing valve for pouring liquid from a liquid-containing bag. The dispensing valve includes a valve body, a cap and a valve member. The valve body includes a rim, a front wall, a guide channel, a frusto-conical section and a cylindrical outlet section. The cylindrical outlet section includes a bearing hole. The front wall is provided with finger grips. The lower portion of the cylindrical outlet section is cut away to form a rectangular outlet orifice. The cap includes a circular rear wall. The circular rear wall includes a plurality of resilient flexible fingers and a plurality of inlet holes. The valve member includes a camming surface, a cylindrical portion, a conical rear portion, an actuating portion and a valve boss. 
     The actuating portion is located within the bearing hole and the bearing hole acts as a guide for the actuation portion. The valve boss slides within the guide channel, thereby opening and closing the rectangular outlet orifice. The rim is coupled with a fitting of the liquid-containing bag. The cap is located within the valve member, such that the resilient flexible fingers make contact with the camming surface. When the actuating portion is pushed against the finger grips, the rectangular outlet orifice opens and the liquid flows out from the liquid-containing bag, through the inlet holes and the rectangular outlet orifice. When the actuating portion is released, the resilient flexible fingers force the valve member against the camming surface, such that the actuating portion moves out through the bearing hole and the valve boss obstructs the rectangular outlet orifice, thereby preventing the liquid to flow out of the liquid-containing bag. 
     U.S. Pat. No. 5,785,196 issued to Montgomery and entitled “Closure for a Pressurized Container”, is directed to a closure for closing the neck of a container package which contains a pressurized liquid, such as a carbonated beverage. The closure includes a planar top, an annular skirt, an annular flange, a plurality of circumferentially spaced radially passages and a plurality of circumferentially spaced axially extending passages. The annular skirt extends downwardly from the planar top and the annular skirt includes an internal thread for screwing the closure on the external threads of the neck. The annular flange extends downwardly from the planar top and diverges toward an inner wall of the neck, to make contact with the inner wall. 
     When the closure is screwed onto the neck, the container pressure within the container package applies a sealing force on the annular flange, thereby moving the annular flange outwardly toward the inner wall and sealing the annular flange against the inner wall. When the force is applied to the annular flange outwardly relative to the planar top, the air trapped between the annular flange and the planar top exits through the circumferentially spaced radially passages, thereby allowing the annular flange to move outwardly. When the closure is unthreaded, the container pressure is relieved through the circumferentially spaced axially extending passages. 
     SUMMARY OF THE DISCLOSED TECHNIQUE 
     It is an object of the disclosed technique to provide a novel device for dispensing a carbonated liquid from a container, which overcomes the disadvantages of the prior art. 
     In accordance with the disclosed technique, there is thus provided a liquid dispenser for dispensing a carbonated liquid from a container. The liquid dispenser includes a compartment, a container sealing region, a compartment sealing region, and a valve. The compartment extends upwardly from a neck portion of the container. The neck portion and the compartment define an opening to the atmosphere between the compartment and the neck portion. The container sealing region is located between the neck portion and the opening. The compartment sealing region is located between the compartment and the opening. 
     The valve is movable within the compartment, from a closed position pressed toward the neck portion, to an open position away from the neck portion. The valve includes a first surface facing the compartment, a second surface facing the opening, a first valve sealing region, a second valve sealing region, and a channel extending from the neck portion to the compartment. The first valve sealing region matches the container sealing region, for preventing passage of fluids between the neck portion and the opening, when the valve is in the closed position. The second valve sealing region matches the compartment sealing region, for preventing passage of fluids between the compartment and the opening, when the valve is in the closed position. The channel enables passage of fluid from the neck portion to the compartment. 
     In accordance with another aspect of the disclosed technique, there is thus provided a liquid dispenser for dispensing a carbonated liquid from a container. The liquid dispenser includes a compartment located above a neck portion of the container, a fluid channel which couples the compartment with the neck portion, a compartment sealing region for sealing the compartment against an opening to the atmosphere, a container sealing region for sealing the neck portion against the opening, and an elastic valve. The elastic valve is firmly attached to the compartment at the compartment sealing region. The elastic valve is elastically deformable to move from a closed position pressed toward the container sealing region, to an open position away from the container sealing region. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: 
         FIG. 1A  is a schematic illustration of a cross section of a dispenser in a closed mode, constructed and operative in accordance with an embodiment of the disclosed technique; 
         FIG. 1B  is a schematic illustration in perspective, of the cover of the dispenser of  FIG. 1A ; 
         FIG. 1C  is a schematic illustration of a free body diagram of the valve element of the dispenser of  FIG. 1A ; 
         FIG. 1D  is a schematic illustration of the dispenser of  FIG. 1A , in a dispensing mode; 
         FIG. 1E  is a schematic illustration of a free body diagram of the valve element of the dispenser of  FIG. 1A , in a dispensing mode; 
         FIG. 1F  is a schematic illustration of the valve element of the dispenser of  FIG. 1A , constructed and operative in accordance with another embodiment of the disclosed technique; 
         FIG. 2  is a schematic illustration of a cross section of a dispenser in a dispensing mode, constructed and operative in accordance with a further embodiment of the disclosed technique; 
         FIG. 3A  is a schematic illustration of a cross section of a dispenser in a closed mode, constructed and operative in accordance with another embodiment of the disclosed technique; 
         FIG. 3B  is a schematic illustration in perspective, of the valve element of the dispenser of  FIG. 3A ; 
         FIG. 3C  is a schematic illustration in perspective, of the valve element of the dispenser of  FIG. 3A  at another view; 
         FIG. 3D  is a schematic illustration of the dispenser of  FIG. 3A , in a dispensing mode; 
         FIG. 4  is a schematic illustration of a cross section of a dispenser in a closed mode, constructed and operative in accordance with a further embodiment of the disclosed technique; 
         FIG. 5  is a schematic illustration of a cross section of a dispenser in a closed mode, constructed and operative in accordance with another embodiment of the disclosed technique; 
         FIG. 6A  is a schematic illustration of a side cross section of a dispenser in a closed mode, constructed and operative in accordance with a further embodiment of the disclosed technique; 
         FIG. 6B  is a schematic illustration of another side cross section of the dispenser of  FIG. 6A ; 
         FIG. 6C  is a schematic illustration of a top cross section (cross section A-A) of the dispenser of  FIGS. 6A and 6B ; 
         FIG. 6D  is a schematic illustration of a perspective of the side cross section of the dispenser of  FIG. 6A ; 
         FIG. 6E  is a schematic illustration of a perspective of the side cross section of the dispenser of  FIG. 6B ; 
         FIG. 6F  is a schematic illustration of a perspective from the bottom of a cover of the dispenser of  FIGS. 6A and 6B ; 
         FIG. 6G  is a schematic illustration of the dispenser of  FIG. 6A  in a dispensing mode; 
         FIG. 7A  is a schematic illustration of a cross section of a dispenser in a closed mode, constructed and operative in accordance with another embodiment of the disclosed technique; 
         FIG. 7B  is a schematic illustration in perspective, of the valve element of the dispenser of  FIG. 7A ; 
         FIG. 7C  is a schematic illustration in perspective, of the valve element of the dispenser of  FIG. 7A  at another view; 
         FIG. 7D  is a schematic illustration of a section of the dispenser of  FIG. 7A ; 
         FIG. 7E  is a schematic illustration of the dispenser of  FIG. 7A , in a dispensing mode; and 
         FIG. 8  is a schematic illustration of a cross section of a dispenser in a dispensing mode, constructed and operative in accordance with a further embodiment of the disclosed technique. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The disclosed technique overcomes the disadvantages of the prior art by providing a valve which seals the mouth of a container containing a carbonated liquid, mainly due to a net force on a valve element, as a result of the gas pressure of the carbonated liquid. This net force is substantially equal to the vectorial sum of the forces acting on different sides of the valve element having different surface areas as a result of the gas and atmospheric pressure. When the container is tilted to a pouring position, the valve element lifts off the mouth due to the gravitational force of the valve element, the gravitational force of the carbonated liquid, or both, thereby allowing the carbonated liquid to flow out of the container under the gas pressure. 
     Reference is now made to  FIGS. 1A ,  1 B,  1 C,  1 D  1 E and  1 F.  FIG. 1A  is a schematic illustration of a cross section of a dispenser in a closed mode, generally referenced  100 , constructed and operative in accordance with an embodiment of the disclosed technique.  FIG. 1B  is a schematic illustration in perspective, of the cover of the dispenser of  FIG. 1A .  FIG. 1C  is a schematic illustration of a free body diagram of the valve element of the dispenser of  FIG. 1A .  FIG. 1D  is a schematic illustration of the dispenser of  FIG. 1A , in a dispensing mode.  FIG. 1E  is a schematic illustration of a free body diagram of the valve element of the dispenser of  FIG. 1A , in a dispensing mode.  FIG. 1F  is a schematic illustration of the valve element of the dispenser of  FIG. 1A , generally referenced  158 , constructed and operative in accordance with another embodiment of the disclosed technique. 
     With reference to  FIGS. 1A and 1B , dispenser  100  includes a cover  102  and a valve element  104 . Cover  102  includes a head portion  106 , a side wall  108 , a pressure-building valve-seat  110 , a plurality of ribs  112  and a guiding element  114 . Valve element  104  is in shape of a frustum of a cone, having a cone angle α, a base  116 , a vertex  118 , a lateral surface  120  and a bore  122  (i.e., a channel from one side to the other). Each of cover  102  and guiding element  114  is made of a substantially rigid material, such as polymer, metal, glass, wood, and the like. Valve element  104  is made of a substantially flexible material, such as plastic, silicone, urethane, rubber (i.e., polymer), and the like. 
     Head portion  106  is substantially circular. Side wall  108  extends from head portion  106 , in a direction substantially normal to head portion  106 . Ribs  112  extend from side wall  108  in the direction of side wall  108 . Pressure-building valve-seat  110  is in form of an annulus coupled with an inner surface (not shown) of side wall  108 . The surface of pressure-building valve-seat  110  is substantially perpendicular to the inner surface of side wall  108 . Pressure-building valve-seat  110 , the inner surface of side wall  108  and the inner surface (not shown) of head portion  106 , form a cover space  124 . Inner edges  126  of ribs  112  form a plurality of openings  128 . 
     Alternatively, the head portion is substantially in form of a hemisphere and the cover is devoid of the side wall. In this case, the cover space is formed by the concave side of the head portion and the cover valve-seat. 
     Guiding element  114  is coupled with the inner surface of head portion  106 , at the center (not shown) of head portion  106 . Guiding element  114  extends from head portion  106  in a direction substantially perpendicular to the inner surface of head portion  106 . The outer diameter (not shown) of guiding element  114  is smaller than the inner diameter (not shown) of bore  122 . 
     Outer edges  130  of ribs  112  are coupled with an edge  132  of a neck  134  of a container  136 . Outer edges  130  can be coupled with edge  132  by fastening methods known in the art, such as by an adhesive, ultrasonic welding, brazing (for metallic parts), welding, electromagnetic forming, and the like. Neck  134  includes a container valve-seat  138 . 
     Alternatively, ribs  112 , side wall  108 , pressure-building valve-seat  110  and container valve-seat  138  are integral parts of neck  134 . In this case, head portion  106  is coupled with side wall  108 , after placing valve element  104  on pressure-building valve-seat  110  and container valve-seat  138 . Further alternatively, guiding element  114  can be an integral part of head portion  106 . 
     Container valve-seat  138  is coupled with an inner wall  142  of neck  134 . Container valve-seat  138  is substantially parallel with pressure-building valve-seat  110 . The distance between container valve-seat  138  and pressure-building valve-seat  110  is designated by the letter L. An inner diameter (not shown) of pressure-building valve-seat  110  is larger than an inner diameter (not shown) of container valve-seat  138 . Valve element  104  is located in such a position, that base  116  is located in cover space  124  and vertex  118  is located in a neck space  140 , neck space  140  being defined by inner wall  142 , container valve-seat  138  and the surface of a carbonated liquid  152  contained in container  136 . 
     Cone angle α, the distance L between pressure-building valve-seat  110  and container valve-seat  138 , and inner diameters (not shown) of pressure-building valve-seat  110  (i.e., compartment sealing region) and container valve-seat  138  (i.e., container sealing region) are selected such that lateral surface  120  (i.e., a second valve sealing region of lateral surface  120 —not shown, and a first valve sealing region of lateral surface  120 —not shown) is simultaneously in contact with both pressure-building valve-seat  110  and container valve-seat  138 , respectively. Valve element  104  is assembled within cover  102 , such that guiding element  114  is located within bore  122 . Hence, valve element  104  can move on guiding element  114  in directions designated by arrows  144  and  146 . A cap  148  having internal threads (not shown), can be screwed on neck  134  having external threads  150  compatible with the internal threads of cap  148 . Carbonated liquid  152  generates gases  154  within neck space  140 . 
     With further reference to  FIG. 1C , S 1  is the net area of vertex  118  (i.e., excluding the base area of bore  122 ), S 2  is the net area of base  116  (i.e., excluding the base area of bore  122 ), M v  is the mass of valve element  104 , P is the pressure of gas  154  within neck space  140  and g is the gravitation constant. The weight of valve element  104 , M v g acts on valve element  104  in direction  146 . A force F 1  acts on vertex  118  in direction  144 , as a result of pressure P of gas  154  within neck space  140 , where,
 
 F   1   P·S   1   (1)
 
Gas  154  enters cover space  124  through bore  122  and thus a force F 2  acts on base  116  in direction  146 , as a result of pressure P of gas  154  within cover space  124 , where,
 
 F   2   =P·S   2   (2)
 
Since
 
 S   2   &gt;S   1   (3)
 
then
 
 F   2   &gt;F   1   (4)
 
Furthermore, since
 
 F   2   +M   v   g&gt;F   1   (5)
 
valve element  104  tends to move in direction  146 , thereby simultaneously sealing pressure-building valve-seat  110  and container valve-seat  138  and preventing gas  154  to escape neck space  140 . At this stage cover space  124  is a pressurized chamber, formed by pressure-building valve-seat  110 , head portion  106  and base  116 , as a result of sealing of pressure-building valve-seat  110 . It is noted that the resiliency of valve element  104  is such that even if cone angle α, distance L and the inner diameters of pressure-building valve-seat  110  and container valve-seat  138  are not exactly at the appropriate values, lateral surface  120  can still seal pressure-building valve-seat  110  and container valve-seat  138 , simultaneously.
 
     It is noted that the sealing action of valve element  104  is caused by a net force F n , wherein,
 
 F   n   =F   2   +M   v   g−F   1   (6)
 
Since the weight of valve element  104 , M v g is constant, a differential force
 
 F   d   =F   2   −F   1   (7)
 
is the determining force in sealing pressure-building valve-seat  110  and container valve-seat  138 . Furthermore, according to Equations 1, 2 and 7,
 
 F   d   =P ( S   2   −S   1 )  (8)
 
As long as pressure P is not zero (i.e., even though pressure P is substantially-low due to repeated consumption of carbonated liquid  152 ), still according to Equation 3, F d &gt;0 and F n &gt;0. Thus, whenever container  136  is in an upright position as in  FIG. 1A , pressure-building valve-seat  110  and container valve-seat  138  are sealed and gas  154  remains within container  136 .
 
     With reference to  FIGS. 1D and 1E , container  136  is tilted at a pouring angle β, wherein carbonated liquid  152  fills neck space  140  and gas  154  fills a bottom space  156  of container  136 . Gas  154  in bottom space  156  is at pressure P. Carbonated liquid  152  has a mass M L . At pouring angle β, a force F 3  acts on vertex  118  as a result of pressure P and the mass M L  of carbonated liquid  152 . Thus,
 
 F   3   =P·S   1   +M   L   g  Sin β  (9)
 
Furthermore, a component of the weight of valve element  104  at pouring angle β and equivalent to M v g Sin β, acts on valve element  104 . Force F 3  together with the component of the weight of carbonated liquid M L  at pouring angle β, force valve element  104  to move on guiding element  114  toward head portion  106 , thereby lifting valve element  104  off of pressure-building valve-seat  110  and container valve-seat  138 . In this position, pressure P of gas  154  forces carbonated liquid  152  out through openings  128 .
 
     When container  136  is returned to an upright position as in  FIG. 1A , the weight of valve element  104  causes valve element  104  to move in direction  146  along guiding element  114  and for lateral surface  120  to make contact with pressure-building valve-seat  110  and container valve-seat  138 . The differential force F d  (Equation 7) further aids valve element  104  to seal pressure-building valve-seat  110  and container valve-seat  138 , thereby preventing gas  154  to escape neck space  140 . 
     It is noted that the disclosed technique allows a user to dispense a carbonated liquid from a container, without actuating the dispenser, wherein the dispenser seals the mouth of the container, when the container is not being used. The dispenser changes from a closed mode to a dispensing mode, when the container is tilted and from the dispensing mode back to the closed mode when the container is returned to the upright position, all transitions taking place automatically, without the intervention of the user. 
     At the pouring stage the carbonated liquid is forced out of the openings under the gas pressure. Thus, it is further noted that the flow of the carbonated liquid out of the container at the pouring stage, is substantially continuous and that no air breathing (as in a conventional opened cap bottle), is necessary. 
     Instead of carbonated liquid, the container can contain a mixture of any chemical substance in a fluid phase and any propellant in a gaseous phase. The chemical substance can be for example, a paint solution, a substance which turns into foam when mixed with air, a substance which transfers from fluid to gas when it is depressurized, such as liquid natural gas (LNG), a substance which vaporizes when exits the container, such as deodorant, and the like. In any case, it is noted that the specific gravity of the valve element must be sufficiently high in order to overcome the differential force F d  (Equation 7), and thus allow the fluid to exit the container. 
     Alternatively, only the portions of lateral surface  120  which serve to seal container valve-seat  138  and pressure-building valve-seat  110  are formed with the cone angle α, and other portions of lateral surface  120  are in form of a prism whose base is a polygon, such as square, rectangle, triangle, pentagon, hexagon, or a close curve, such as circle, ellipse, and the like. With reference to  FIG. 1F , valve element  158  is in form of a right circular cone instead of a frustum of a cone, such as valve element  116  (i.e., valve element  158  is devoid of a vertex similar to vertex  118 ). 
     Reference is now made to  FIG. 2 , which is a schematic illustration of a cross section of a dispenser in a dispensing mode, generally referenced  200 , constructed and operative in accordance with a further embodiment of the disclosed technique. Dispenser  200  includes a first cover  202  (i.e., outer cover), a second cover  204  (i.e., inner cover) and a valve element  206 . First cover  202  includes a first side wall  208  and a first head portion  210 . First head portion  210  is provided with at least one port  212 . Second cover  204  includes a second side wall  214 , a second head portion  216 , a pressure-building valve-seat  218  and a plurality of ribs  220 . 
     Second cover  204  is similar to cover  102  ( FIGS. 1A and 1B ), except that second side wall  214  is thicker than side wall  108 . The inner edges (not shown) of ribs  220  form a plurality of openings  222 . Valve element  206  is provided with a bearing portion  224 , thereby allowing valve element  206  to slide within an inner surface (not shown) of second side wall  214 , is directions designated by arrows  226  and  228 . 
     First head portion  210  is substantially circular. First side wall  208  extends from first head portion  210 , in a direction substantially perpendicular to first head portion  210 . A tail portion  230  of first side wall  208 , opposite to first head portion  210 , is coupled with an edge  232  of a neck  234  of a container  236 . Neck  234  includes a container valve-seat  238 . The inner surfaces (not shown) of first cover  202  and the outer surfaces (not shown) of second cover  204  define an inter-cover space  240 . 
     Alternatively, the first head portion is substantially in form of a hemisphere and the first cover is devoid of the first side wall. In this case, the inter-cover space is formed by the concave side of the first head portion and the outer surfaces of the first cover. 
     When container  236  is tilted as in  FIG. 2 , the weight of a carbonated liquid  242  contained in container  236 , forces a base (not shown) of valve element  206  toward an inner surface (not shown) of second head portion  216 , wherein valve element  206  lifts off of pressure-building valve-seat  218  and container valve-seat  238 . Gases (not shown) located at a bottom space (not shown) of container  236  force carbonated liquid  242 , to flow through openings  222  to inter-cover space  240  and out of container  236 , through port  212 . 
     When container  236  is moved to an upright position similar to that of  FIG. 1A , the weight of valve element  206  causes valve element  206  to slide within the inner surface of second side wall  214  in direction  226 . The lateral surfaces (not shown) of valve element  206  make contact with pressure-building valve-seat  218  and container valve-seat  238 , and the pressure of the gas causes valve element  206  to seal pressure-building valve-seat  218  and container valve-seat  238 , in a manner similar to the one described herein above in connection with  FIG. 1A . Thus, when container  236  is in the upright position, the pressure of the gas within container  236  aids valve element  206  to seal container valve-seat  238  and prevent the escape of the gas from container  236 . 
     Alternatively, container valve-seat  238  is an integral part of first side wall  208  and first head portion  210  is a separate part. Hence, after attaching second cover  204  to neck  234 , first cover  202  is coupled with neck  234 , and first head portion  210  is coupled with first side wall  208 . Further alternatively, container valve-seat  238  and second side wall  214  are integral parts of neck  234 , second head portion  216  is a separate part, and first head portion  210  is an integral part of first side wall  208 . In this case, after inserting valve element  206  within second cover  204 , second head portion  216  is coupled with second side wall  214  and first cover  202  is coupled with edge  232 . 
     Reference is now made to  FIGS. 3A ,  3 B,  3 C and  3 D.  FIG. 3A  is a schematic illustration of a cross section of a dispenser in a closed mode, generally referenced  280 , constructed and operative in accordance with another embodiment of the disclosed technique.  FIG. 3B  is a schematic illustration in perspective, of the valve element of the dispenser of  FIG. 3A .  FIG. 3C  is a schematic illustration in perspective, of the valve element of the dispenser of  FIG. 3A  at another view.  FIG. 3D  is a schematic illustration of the dispenser of  FIG. 3A , in a dispensing mode. 
     With reference to  FIGS. 3A ,  3 B and  3 C, dispenser  280  includes a cover  282  and a valve element  284 . Cover  282  includes a head portion  286 , a side wall  288 , a pressure-building valve-seat  290  and a plurality of ribs  292 . Pressure-building valve-seat  290 , an inner surface (not shown) of side wall  288  and an inner surface (not shown) of head portion  286 , form a cover space  294 . Ribs  292  form a plurality of openings  296 . Valve element  284  is in form of a multi-faceted object (e.g., sewing bobbin) having a first end portion  298 , a second end portion  300  and a mid-portion  302 . The diameters of first end portion  298 , second end portion  300  and mid-portion  302  are designated by D 1 , D 2  and D 3 , respectively, such that
 
 D   1   &gt;D   2   (10)
 
 D   3   &lt;D   1   (11)
 
and
 
 D   3   &lt;D   2   (12)
 
     First end portion  298  and second end portion  300  are provided with a first hole  304  and a second hole  306 , respectively. The diameters of first hole  304  and second hole  306  are designated by D 4  and D 5 , respectively, such that
 
 D   4   &lt;&lt;D   5   (13)
 
Furthermore, a depth of second hole  306  designated by L, is such that valve element  284  is provided with a cavity  308  within mid-portion  302 .
 
     A neck  310  of a container  312  is provided with a container valve-seat  314 . The inner diameters (not shown) of pressure-building valve-seat  290  and container valve-seat  314  are substantially equivalent. D 1  is greater than an inner diameter (not shown) of pressure-building valve-seat  290 . D 3  is substantially equal to the inner diameter of pressure-building valve-seat  290 . D 5  is smaller than an inner diameter (not shown) of container valve-seat  314 . D 2  is greater than the inner diameter of container valve-seat  314 . Thus, the effective surface area (not shown) of first end portion  298  (i.e., the surface area of first end portion  298  excluding the area of first hole  304 ), is substantially greater than the effective surface area (not shown) of second end portion  300  [i.e., an annular area (not shown) defined by container valve-seat  314  and second hole  306 ]. 
     Mid-portion  302  is located within pressure-building valve-seat  290 , such that valve element  284  can move in directions designated by arrows  316  and  318 . The outer edges (not shown) of ribs  292  are coupled with an edge (not shown) of neck  310 . Container  312  contains a carbonated liquid  320  and a neck space  324  of container  312  contains a gas  326  at a pressure P. 
     When container  312  is in an upright position, the weight of valve element  284  forces valve element  284  to move in direction  318 , wherein first end portion  298  and second end portion  300  make contact with pressure-building valve-seat  290  and with container valve-seat  314 , respectively. Gas  326  enters cover space  294  through first hole  306  and second hole  304 . The effective surface area of first end portion  298  exposed to gas  326  within cover space  294 , is substantially greater than the effective surface area of second end portion  300  exposed to gas  326  in neck space  324 . Thus, the force acting on first end portion  298  as a result of pressure P, is substantially greater than the force acting on second end portion  300  as a result of pressure P. The difference between these two forces, aids in sealing of pressure-building valve-seat  290  and of container valve-seat  314 , by first end portion  298  and second end portion  300 , respectively, thereby preventing gas  326  to escape from container  312 . 
     With reference to  FIG. 3D , container  312  is tilted at a pouring angle (not shown). At this pouring angle, carbonated liquid  320  fills cavity  308  and the weight of carbonated liquid  320  within cavity  308  forces valve element  284  to move in direction  316 . Second end portion  300  lifts off of container valve-seat  314  and valve element  284  stops to move when second end portion  300  makes contact with pressure-building valve-seat  290 . Gas  326  which is located at a bottom space (not shown) of container  312 , forces carbonated liquid  320  out of container  312  through openings  296 . 
     Valve element  284  is made of a substantially flexible material. Hence, valve element  284  can be assembled on cover  282  by inserting first end portion  298  through pressure-building valve-seat  290  and then cover  282  can be coupled with the edge of neck  310 . Alternatively, ribs  292 , side wall  288  and pressure-building valve-seat  290  are integral parts of neck  310 , and head portion  286  is a separate part. In this case, valve element  284  can be assembled on cover  282  by inserting second end portion  300  through pressure-building valve-seat  290  and through cover space  294 , and then head portion  286  can be coupled with side wall  288 . 
     Alternatively, the cross section of the mid-portion of the valve element is any polygon or closed curve, such as square, rectangle, triangle, ellipse, and the like. Accordingly, the opening of the pressure-building valve-seat is made in a shape which matches the cross section of the mid-portion. Furthermore, the cross section of the mid-portion can be variable along direction  316 . For example, this cross section can be in form of a cone or an undulating surface. 
     It is further noted that each of the first end portion and the second end portion can be in form of a polygon or a closed curve. Likewise, the opening of each of the pressure-building valve-seat and the container valve-seat can be made in shape of a polygon or a closed curve, such that the first end portion seals the pressure-building valve-seat and the second end portion seals the container valve-seat. It is noted that the perimeter of each of the first hole and the second hole can be in shape of any polygon or closed curve. 
     In the example set forth in  FIG. 3A , the inner diameters of the container valve-seat and the pressure-building valve-seat are substantially equal. These two inner diameters however, can be different, provided the effective surface area of the first end portion is substantially greater than that of the second end portion and that the valve element can move between the two sealing and unsealing positions. It is further noted that D 3  must be smaller than D 1 . However, D 3  can be substantially equal to or less than D 2 . 
     Reference is now made to  FIG. 4 , which is a schematic illustration of a cross section of a dispenser in a closed mode, generally referenced  350 , constructed and operative in accordance with a further embodiment of the disclosed technique. Dispenser  350  includes a cover  352 , a valve element  354  and a plurality of conduits  356 . Cover  352  includes a pressure-building valve-seat  358  and a plurality of ribs  360 . Valve element  354  is in shape of a frustum of a cone, having a base  362 , a vertex  364  and a lateral surface  366 . The surface area (not shown) of base  362  is greater than that of vertex  364 . Valve element  354  includes an inner body  368  and an outer layer  370 . The specific gravity of inner body  368  is sufficiently high in order to overcome the differential force F d  (Equation 7), and thus allow the fluid to exit the container. Inner body  368  can be made of a material having a substantially large specific gravity, such as lead, iron, stone, glass, and the like. 
     Ribs  360  are coupled with an edge  372  of a neck  374  of a container (not shown). Inner edges (not shown) of ribs  360  form a plurality of openings  376 . Neck  374  includes a container valve-seat  378 . Outer layer  370  is made of a substantially flexible material similar to that of valve element  104 , as described herein above in connection with  FIG. 1A . Hence, lateral surface  366  can efficiently seal pressure-building valve-seat  358  and container valve-seat  378 . 
     Pressure-building valve-seat  358  is coupled with container valve-seat  378  by conduits  356 , such that a neck space  380  is in communication with a cover space  382 . The container contains a carbonated liquid (not shown) and neck space  380  contains a gas (not shown) at a pressure P. 
     Outer layer  370  makes contact with pressure-building valve-seat  358  and with container valve-seat  378 , due to the weight of inner body  368 . The gas enters cover space  382  through conduits  356 . Since the surface area of base  362  is greater than that of vertex  364 , the force acting on base  362  as a result of pressure P of the gas, is greater than the force acting on vertex  364  as a result of pressure P of the gas. The difference in these two forces aids in sealing pressure-building valve-seat  358  and container valve-seat  378 , thereby preventing the gas to escape from the container. 
     When the container is tilted at a pouring angle (not shown), the weight of the carbonated liquid causes valve element  354  to lift off of pressure-building valve-seat  358  and container valve-seat  378 , and the carbonated liquid pours out of the container through openings  376 . It is noted that since valve element  354  does not include any bore, such as bore  122  ( FIG. 1A ), the construction of valve element  354  is substantially simple. Furthermore, the weight of inner body  368  aids in moving valve element  354  toward pressure-building valve-seat  358  and container valve-seat  378 , when the container is moved from a dispensing position to an upright position. 
     Reference is now made to  FIG. 5 , which is a schematic illustration of a cross section of a dispenser in a closed mode, generally referenced  410 , constructed and operative in accordance with another embodiment of the disclosed technique. Dispenser  410  includes a cover  412 , a valve element  414  and a flexible rib  416 . Cover  412  includes a pressure-building valve-seat  418 . Valve element  414  is similar to valve element  104 , as described herein above in connection with  FIG. 1A . Valve element  414  has a cone angle α. An edge  420  of cover  412  is coupled with an edge  422  of a neck  424  of a container (not shown), by flexible ribs  416 . Neck  424  includes a container valve-seat  426 . A distance between pressure-building valve-seat  418  and container valve-seat  426  is designated by L. 
     Each of flexible ribs  416  is made of a resilient material, such as silicone, urethane, rubber (i.e., polymer), and the like, thereby allowing cover  412  to move in directions designated by arrows  428  and  430 , relative to neck  424 . If rigid ribs are employed instead of flexible ribs  416  and if the values of cone angle α, distance L, the inner diameters (not shown) and the concentricity (not shown) of the pressure-building valve-seat and the container valve-seat, and the like are not compatible, then the valve element can not completely seal the pressure-building valve-seat and the container valve-seat. However, if flexible ribs  416  are employed, then the movement of cover  412  in directions  428  and  430  compensates for the lack of compatibility of these values, thereby allowing valve element  414  to seal pressure-building valve-seat  418  and container valve-seat  426 , effectively, due to the pressure of the gas. 
     In accordance with another aspect of the disclosed technique, a first area of a first side of a diaphragm is exposed to the gas pressure and a second area on a second side of the diaphragm, larger than the first area, is exposed to the same gas pressure. Since the force due to the gas pressure on the second side is greater than the one on the first side, the diaphragm closes against the mouth of the container and prevents the gas to escape. When the container is tilted at a pouring angle, the mass of the carbonated liquid forces the diaphragm open and the carbonated liquid emerges through this opening. 
     Reference is now made to  FIGS. 6A ,  6 B,  6 C,  6 D,  6 E,  6 F and  6 G.  FIG. 6A  is a schematic illustration of a side cross section of a dispenser in a closed mode, generally referenced  450 , constructed and operative in accordance with a further embodiment of the disclosed technique.  FIG. 6B  is a schematic illustration of another side cross section of the dispenser of  FIG. 6A .  FIG. 6C  is a schematic illustration of a top cross section (cross section A-A) of the dispenser of  FIGS. 6A and 6B .  FIG. 6D  is a schematic illustration of a perspective of the side cross section of the dispenser of  FIG. 6A .  FIG. 6E  is a schematic illustration of a perspective of the side cross section of the dispenser of  FIG. 6B .  FIG. 6F  is a schematic illustration of a perspective from the bottom of a cover of the dispenser of  FIGS. 6A and 6B .  FIG. 6G  is a schematic illustration of the dispenser of  FIG. 6A  in a dispensing mode. 
     With reference to  FIGS. 6A ,  6 B,  6 C,  6 D,  6 E and  6 F, dispenser  450  includes a neck section  452 , a cover  454  and a diaphragm  456  (i.e., an elastic valve or a membrane). Neck section  452  includes a lower annulus  458 , an upper annulus  460 , an inner annular wall  462 , an outer annular wall  464 , a plurality of inner ribs  468  and a plurality of outer ribs  470 . Lower annulus  458  and upper annulus  460  are coupled by outer annular wall  464 , inner ribs  468  and by outer ribs  470 . Inner annular wall  462  extends from lower annulus  458 . The inner diameter of inner annular wall  462  is referenced D 6 , the inner diameter of outer annular wall  464  is referenced D 7 , and the outer diameter of upper annulus  460  is referenced D 8 , such that,
 
 D   7   &gt;D   6   (14)
 
and
 
 D   8   &gt;D   7   (15)
 
     The space within inner annular wall  462  forms a base opening  472 . The space between inner annular wall  462  and outer annular wall  464  forms a diaphragm-base chamber  474 . A base intermediate chamber  476  is formed between lower annulus  458 , upper annulus  460 , outer annular wall  464 , inner ribs  468  and outer ribs  470 . A plurality of openings  478  are formed between every pair of outer ribs  470 . Outer annular wall  464  is provided with a plurality of holes  480 . Each of inner ribs  468  is provided with a hole  482 , which passes from lower annulus  458  to upper annulus  460 . 
     Cover  454  includes a head portion  484 , an inner annular wall  486  and an outer annular wall  488 . Inner annular wall  486  and outer annular wall  488  extend from head portion  484 . An edge  490  (i.e., a compartment sealing region) of inner annular wall  486  is provided with a plurality of notches  492 . The cross section of each of notches  492  can be semi-circular, elliptical, or polygonal, such as square, rectangle, triangle, and the like. Diaphragm  456  includes a body  494  (i.e., massive body). The inner diameter of inner annular wall  486  is referenced D 9 , the outer diameter of outer annular wall  488  is referenced D 10  and the diameter of diaphragm  456  is referenced D 11 , such that,
 
 D   10   &gt;D   9   (16)
 
 D   11   &gt;D   7   (17)
 
 D   9   ≧D   7   (18)
 
 D   9   &gt;D   6   (19)
 
and
 
 D   10   ≈D   8   (20)
 
     Each of neck section  452 , cover  454  and diaphragm  456  has a substantially circular cross section. However, it is noted that the cross section of each of neck section  452 , cover  454  and diaphragm  456  can be non-circular, such as ellipse, square, rectangular, triangular, polygonal, and the like. 
     Each of neck section  452  and cover  454  is made of a polymer, such as injection molded plastic, a molded metal, such as zinc die casting, and the like. Neck section  452  can be made of two parts which are fastened together at cross section A-A. Diaphragm  456  is made of a substantially thin and flexible material, such as natural rubber, synthetic rubber, urethane, silicone (i.e., a polymer), and the like. Each of neck section  452 , cover  454 , diaphragm  456  and body  494  is made of a nontoxic material. The specific gravity of body  494  is substantially greater than that of diaphragm  456 . 
     Cover  454  is coupled with neck section  452 , such that edge  490  and an edge  496  of outer annular wall  488 , make contact with upper annulus  460 . Cover  454  and neck section  452  can be coupled together by fastening methods known in the art, such as by an adhesive, ultrasonic welding, brazing (for metallic parts), welding, electromagnetic forming, and the like. Diaphragm  456  is located between edge  490  and upper annulus  460 . 
     Neck section  452  is coupled with a neck  498  of a container  500 . Alternatively, neck section  452  is integral with neck  498 . Container  500  contains a carbonated liquid  502  and a gas  504  at a pressure P, fills a neck space  506 , defined by an inner wall (not shown) of neck  498 , lower annulus  458  and carbonated liquid  502 . 
     A diaphragm-cover chamber  508  (i.e., a compartment) is formed between head portion  484 , inner annular wall  486  and diaphragm  456 . The space between head portion  484 , inner annular wall  486 , outer annular wall  488  and upper annulus  460  forms a cover intermediate chamber  510 . 
     Neck space  506  communicates with cover intermediate chamber  510  through holes  482 . Cover intermediate chamber  510  communicates with diaphragm-cover chamber  508  through notches  492 . Thus, neck space  506  communicates with diaphragm-cover chamber  508 , through holes  482 , cover cavity  510  and notches  492  (which together form a fluid channel). 
     Diaphragm-base chamber  474  communicates with base intermediate chamber  476  through holes  480 . Base intermediate chamber  476  is open to the atmosphere through openings  478 . Thus, diaphragm-base chamber  474  is open to the atmosphere through holes  480 , base intermediate chamber  476  and openings  478 . 
     A force F 6  (not shown) acts on diaphragm  456 , as a result of pressure P of gas  504  on an area S 6  (not shown) of diaphragm  456  defined by inner diameter D 6 . A force F 9  (not shown) acts on diaphragm  456 , as a result of pressure P of gas  504  on an area S 9  (not shown) of diaphragm  456  defined by inner diameter D 9 . A force W (not shown) due to the weight of body  494  acts on diaphragm  456 . The force F 6  tends to lift diaphragm  456  off of an edge  512  (i.e., a container sealing region) of inner annular wall  462 . The forces F 6  and W tend to seal diaphragm  456  against edge  512 . 
     Since according to Equation 19,
 
 S   9   &gt;S   6   (21)
 
then,
 
 F   9   &gt;F   6   (22)
 
Thus, a net force
 
 F   n   =F   9   +W−F   6   (23)
 
causes diaphragm  456  to seal against edge  512 , thereby preventing gas  504  to escape container  500 .
 
     With reference to  FIG. 6G , container  500  is tilted at a pouring angle (not shown), wherein carbonated liquid  502  enters base opening  472  and the weight of carbonated liquid  502  in base opening  472  lifts diaphragm  456  off of edge  512 . Gas  504  which fills a bottom space (not shown) of container  500 , forces carbonated liquid  502  out of openings  478 , through diaphragm-base chamber  474 , holes  480  and base intermediate chamber  476 . 
     During emergence of carbonated liquid  502  through openings  478 , a portion of carbonated liquid  502  enters diaphragm-cover chamber  508 , through holes  482 , cover intermediate chamber  510  and notches  492 . When container  500  is returned to an upright position, such as in  FIG. 6A , the weight of this portion of carbonated liquid  502  confined within diaphragm-cover chamber  508 , together with the force F n  (Equation 23) cause diaphragm  456  to seal against edge  512 , thereby keeping gas  504  within container  500 . 
     Reference is now made to  FIGS. 7A ,  7 B,  7 C,  7 D and  7 E.  FIG. 7A  is a schematic illustration of a cross section of a dispenser in a closed mode, generally referenced  530 , constructed and operative in accordance with another embodiment of the disclosed technique.  FIG. 7B  is a schematic illustration in perspective, of the valve element of the dispenser of  FIG. 7A .  FIG. 7C  is a schematic illustration in perspective, of the valve element of the dispenser of  FIG. 7A  at another view.  FIG. 7D  is a schematic illustration of a section of the dispenser of  FIG. 7A .  FIG. 7E  is a schematic illustration of the dispenser of  FIG. 7A , in a dispensing mode. 
     With reference to  FIG. 7A , dispenser  530  includes a compartment  532 , a valve element  534  and a tubing section  536 . Compartment  532  includes a cover  538 , a side wall  540  and a bottom  542 . The cross section of compartment  532  along section B-B is preferably circular, however this cross section can be in the form of any polygon or closed curve, such as square, rectangle, triangle, ellipse, and the like. 
     Bottom  542  is provided with a plurality (n) of openings  544 . Tubing section  536  couples bottom  542  with a neck  546  of a container  548 . Thus, a compartment space  550  of compartment  532  communicates with a neck space  552  of container  548  via a passageway  554  of tubing section  536 . 
     With further reference to  FIGS. 7B and 7C , valve element  534  includes a plurality of ribs  556  at a periphery thereof, and an annular groove  558 . Valve element  534  is provided with an opening  560  approximately at a center (not shown) thereof. Annular groove  558  is located at a bottom surface  562  of valve element  534 . Valve element  534  is located within compartment  532 , such that bottom surface  562  faces openings  544 . 
     The circumference of valve element  534  is similar to that of an inner circumference (not shown) of side wall  540 , such that valve element  534  can move within compartment space  550  in directions designated by arrows  564  and  566 . Ribs  556  guide valve element  534  to move within compartment space  550 . However, the valve element can be devoid of the ribs, wherein the circumference of the valve element is of such size to allow sliding motion of the valve element against the inner circumference of the side wall. 
     Cover  538  is fastened to side wall  540  after inserting valve element  534  in compartment space  550 . Alternatively, bottom  542  is fastened to side wall  540  after inserting valve element  534  in compartment space  550 . Side wall  540 , tubing section  536  and neck  546  can be all be the same part. Alternatively, any of side wall  540 , tubing section  536  and neck  546  can be a separate part, and fastened together by an adhesive, by vibration welding, thermal welding, and the like. 
     Annular groove  558  is filled with a sealing element  568 . A contour of annular groove  558  is such that when a force acts on a top surface  570  of valve element  534 , sealing element  568  seals openings  544 . Alternatively, the valve element can be devoid of the annular groove and the sealing element, in which case the bottom surface of the valve element alone, seals against the openings of the bottom of the compartment. 
     Opening  560  is located such that compartment space  550  can communicate with neck space  552 , through opening  560  and passageway  554 . Container  548  contains a carbonated liquid  572  and neck space  552  contains a gas  574  at a pressure P G . The pressure P G  is substantially greater than the atmospheric pressure P A . 
     With reference to  FIG. 7D , the diameter of top surface  570  is designated D 11 , the diameter of each of openings  544  D 12 , the diameter of opening  560  D 13 , and the diameter of passageway  554  D 14 . The base (not shown) of opening  560 , corresponding to diameter D 13  defines a surface area S 13 . The net surface area of top surface  570  after subtracting S 13  from the total surface area of top surface  570  defined by D 11 , is designated S 11 . The base (not shown) of each the openings  544 , corresponding to diameter D 12 , defines a surface area S 12 . The base (not shown) of passageway  554 , corresponding to diameter D 14 , defines a surface area S 14 . When container  548  is in an upright position as illustrated in  FIG. 7A , valve element  534  drops down within compartment space  550  ( FIG. 7A ) due to the force of gravity M v g, and the pressure in compartment space  550  equalizes to P G . 
     In the example set forth in  FIG. 7D ,
 
 S   13   &lt;S   14   (24)
 
The difference between S 13  and S 14  is designated S NET . The force acting on bottom surface  562  due to the surface area S NET  and the gas pressure P G , is
 
 F   3   =P   G   ·S   NET   (25)
 
The surface area of bottom surface  562  which is exposed to the atmospheric pressure P A , is defined by the sum of surface areas of openings  544  (i.e., nS 12 ). The force acting on bottom surface  562  due to surface area nS 12  and the atmospheric pressure P A , is
 
 F   4   =P   A   ·nS   12   (26)
 
and the force acting on top surface  570  due to the net surface area S 11  and the gas pressure P G , is
 
 F   5   =P   G   ·S   11   (27)
 
Since,
 
 S   11   &gt;S   NET   (28)
 
and
 
 P   G   &gt;P   A   (29)
 
then,
 
 F   5   &gt;F   3   (30)
 
and since,
 
 S   11   &gt;nS   12   (31)
 
then,
 
 F   5   &gt;F   4   (32)
 
The diameters D 12 , D 13 , and D 14  are selected such that
 
 F   5   +M   v   g&gt;F   4   +F   3   (33)
 
Thus, valve element  534  is forced toward openings  544  along arrow  566  ( FIG. 7A ), wherein sealing element  568  seals openings  544  and prevents gas  574  to escape from neck space  552 .
 
     With reference to  FIG. 7E , container  548  is tilted at a pouring angle (not shown). At this pouring angle, carbonated liquid  572  flows through passageway  554  and the weight of carbonated liquid  572  forces valve element  534  to move in direction  564 . Sealing element  568  lifts off openings  544  thereby allowing carbonated liquid  572  to pour out of container  548 , through openings  544 . 
     It is noted with reference to  FIG. 7D , that if
 
 D   13   ≧D   14   (34)
 
then S NET =0, and F 3 =0, and Equation 33 still holds.
 
     Reference is now made to  FIG. 8 , which is a schematic illustration of a cross section of a dispenser in a dispensing mode, generally referenced  590 , constructed and operative in accordance with a further embodiment of the disclosed technique. Dispenser  590  includes a compartment  592 , a valve element  594 , a tubing section  596 , and a plate section  598 . Compartment  592  includes a bottom  600 . Bottom  600  is provided with a plurality of openings  602 . Tubing section  596  couples bottom  600  with plate section  598 . Tubing section  596  includes a passageway  604 . Plate section  598  is coupled with an inner wall  606  of a container  608 , by fastening methods known in the art, such as an adhesive, ultrasonic welding, thermal welding, snap-in connection, and the like. Valve element  594  is in form of a disk and is provided with an opening  610 . Container  608  includes a carbonated liquid  612 . 
     Container  608  is tilted at a pouring angle (not shown). At this pouring angle, carbonated liquid  612  flows through passageway  604  and the weight of carbonated liquid  612  forces valve element  594  to move in a direction designated by an arrow  614 . Valve element  594  lifts off openings  602  thereby allowing carbonated liquid  612  to pour out of container  608 , through passageway  604  and openings  602 . 
     Alternatively, the cross section of the valve element is any polygon or closed curve, such as square, rectangle, triangle, ellipse, and the like. Accordingly, the cross section of the inner wall of the compartment can for example be made in a shape which matches the cross section of the valve element. 
     It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow.