Vented fluid closure and container

A vented closure for a liquid container which will not freely pour includes a cap hinged at one side and movable between open and closed positions relative to a base collar. In an open position, a primary fluid passageway extends through a shaped mouthpiece which is elongated and tapered to conform to a user's mouth. One or more air vents of small size are located in a protected floor of the base collar at positions spaced within predetermined ranges of offsets from the dispensing opening so as to convey liquid into contact with the air vents in a manner to self-seal the air vents by surface tension of the liquid until an unbalance force is present. The cap and collar mate along an offset diagonal edge, and a grip area for the user's thumb or finger is offset from a center line. The offsets cause the cap to flip open with additional clearance and without obstructing a user's nose.

FIELD OF THE INVENTION

The present invention relates generally to vented fluid closures and containers and, more particularly, to a vented closure for a fluid container with a non-pouring type fluid passage when the closure is open.

BACKGROUND OF THE INVENTION

Water and other non-carbonated beverages, and particularly sports drinks, are sold in individual servings in the form of deformable plastic bottles which are squeezable. Such bottles typically have a cap in the form of a pull open/push close type closure, or a flip to open cap, which typically provides a single fluid passage which is not vented. The lack of a vent in the closure causes the deformable container to collapse as a consumer draws a beverage from the container while drinking, due to a pressure differential that is created between the fluid and the exterior of the container, since the external pressure is higher as the exiting liquid causes the internal pressure to decrease. At some point during the drinking process, depending on the size of the container, no additional liquid can be withdrawn from the container until the pressure is equalized by stopping the drinking process and allowing air to rush in through the single fluid passage in the closure. This equalization can cause a reflux or backwash from the consumer's mouth into the container, which tends to contaminate the fluid in the container. Because of these problems, consumers frequently equalize pressure by holding the bottle away from the mouth and squeezing the deformable bottle in a series of squirts, with pressure equalization taking place between each squirt. This procedure often results in spills of the fluid, and results in the consumer drinking less than were it easier to dispense fluid.

Conventional fluid containers are sometimes vented, but the vent typically is part of the container itself, and not part of the closure. Vented closures intended for pouring are known, but are undesirable for use in non-pouring type closures in which fluid will not continuously pour out of the bottle when the bottle is tilted downwardly. Sports bottles are an example of a non-pouring type closure which are intended to be left open for quick drinks during an activity, and can be easily knocked over. In general, pouring type closures are not suitable for sports bottles and other deformable containers in which the liquid exits in spurts due to squeezing of the container and/or placing the user's mouth around the closure opening to draw liquid out of the container.

The manufacturing cost of closures used on sports drink containers and the like is critical. An increase of fractions of one cent can severely impact marketability by the closure manufacturer since consumers usually are focused on the sports beverage or supplier and are generally unwilling to pay more for the bottle and closure which contains the beverage. Likewise, it is very important that any closure should be compatible with existing bottling and assembly equipment and should be usable in connection with standard bottling and assembly processes. The types of closures proposed in the past have been incompatible with these requirements.

The choke hazard posed by relatively small parts and/or separable parts used for closures have caused concern. Small children have been endangered by chewing on closures until the parts became distorted and loose. This problem is particularly troublesome for pull to open and push to close type closures.

One solution to the choke hazard is to use hinged top closures which typically have larger size parts that are molded as one piece. However, these hinged closures can be difficult to open and orient for comfortable use. It is difficult on many hinged top closures to identify the latching area and/or for a user to apply force to the latch to open, because the machinery used to attach the closure to the bottle during filling and assembly requires that nothing protrude from the closure surface. Another concern with hinged top closures is the difficulty for many users to properly orient the closure for opening and use. It is natural for users to rotate the closure so the latch is facing them to facilitate pushing the closure open with the thumb. However, the open hinged cover then tends to align behind the thumb and opposite the consumer's nose when the container is raised to drink. This is an uncomfortable and undesirable condition.

One objective of the present invention is to provide an improved vented fluid container closure of the non-pouring type that is adaptable to a standard beverage container and which are easily adaptable to current beverage filling and processing equipment.

Another objective of the present invention is to provide an improved hinged top closure which allows for easy opening, comfortable use and reduced choke hazard.

A further objective is to provide structure which improves the venting operation, and the dispensing of liquid through a mouthpiece for convenient drinking from a container which can be repeatedly opened and closed.

SUMMARY OF THE INVENTION

In order to achieve the foregoing objectives, the present invention provide non-pouring type closures with a fluid passage and one or more vent passages of predetermined dimensions and placement in a base collar adaptable to a standard beverage container. The fluid passage and the one or more vent passages may be opened and closed by the same cap. When the cap is open and inverted to a drinking position, surface tension of the liquid will seal the one or more vent passages which are in contact with the liquid. The vent openings are sufficiently small in size and placed relative to the main fluid exit so that the weight of the liquid which is in direct contact with the vent openings does not exert sufficient force to overcome surface tension and substantially prevents equalizing air from entering the vent passageways.

When the container is squeezed or the user draws liquid through the mouthpiece, air bubbles enter a vent passageway separated from the flow of exiting liquid by a divider which prevents the air bubbles from becoming entrained. Structure is included to reduce bubble size and noise and improve the venting operation.

An improved hinged type closure includes a flip cap having an orientation relative to an elongated mouthpiece and a structure so as to better orient the closure for use. The cap will open to a side and away from possible interfering positions with the user's face. The mouthpiece has a shape and structure to improve drinking from the closure and reduce spills or leakage. Supplemental stoppers and plugs also prevent leakage due to sudden forces such as can occur, for example, during transport of a pre-filled liquid container.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As seen inFIGS. 1 to 8, a novel vented fluid closure is molded as one piece and includes a top cover or cap20which is movably connected by a hinge22to a base collar24having a central liquid dispensing bore or outlet opening26. The cap20is movable between open positions for dispensing liquid and a closed position as seen inFIG. 5. The collar includes interior threads28for mating engagement with a beverage container. An exterior annual wall of the collar24includes a large plurality of vertical ribs or splines30which are engagable by standard packaging machinery to provide gripping surfaces to assist in threading the interior threads28onto the beverage container after the container has been filled during the manufacturing process. These external ribs30also assist the user in attaching or detaching the closure from the container.

The base collar24and the cap20are adapted to mate with a standard fluid container40which may be any container for containing a fluid, such as a plastic bottle for a single serving of a liquid sport drink or water. The beverage container40preferably has thin plastic side walls42which are squeezable or deformable along arrows44in order to increase pressure within the closed container when liquid is to be dispensed from the container. The container40forms a closed vessel having deformable side walls, a bottom wall, and a top section having an upright annular neck46which is hollow and serves as the sole opening for the passage of fluid out of the container.

The upright annular neck46includes an annular rib48, and located above the rib48are external threads50for mating engagement with the internal threads28of the base collar24. Preferably the cap20and base collar24are molded as a single piece connected by a living hinge22. They can be formed of a high density polyethylene (HDPE) or polypropylene (PPL), but any suitable material may be used. It is possible, but less desirable due to a choke hazard, to mold the cap20and collar24as separate pieces which can be rotatably connected to each other.

One or more small diameter vent apertures60are located in the collar24, seeFIGS. 1 and 4. Each vent aperture60is of a small cross-sectional area and is at a location selected to perform self-sealing by surface tension of liquid in contact with the aperture60. Namely, the cross-sectional area and the location of the vent aperture60relative to the fluid dispensing opening26are selected, as will be explained in connection withFIGS. 9 and 10, to create a self-sealing feature. More than one vent aperture60is useful to increase venting air flow into the container and to prevent possible clogging due to dust or small debris, and two vent apertures are illustrated by way of example.

The cap20includes a central stopper plug62which inserts snuggly into and blocks the liquid bore26when the cap is rotated to a closed position, seeFIG. 7which illustrates the cap20slightly open. The cap20also includes two vent plugs64which extend over and mate with the vents60to form a block for each vent60when the cap20is fully closed. As will be explained, the vent apertures60will self-seal and the main liquid opening26will not leak during normal use until the container40is squeezed or some other unbalance force causes a loss of equilibrium. Such forces can be present in the process of transporting a pre-filled liquid container, and therefore the stoppers62and64are advantageous to supplement the self-sealing function. Also, the cap20which entirely covers all closure openings, and the positive stoppers for the fluid dispensing and venting, assist in preventing tampering and intentional or accidental contamination of the liquid in the container prior to purchase and individual use by a consumer.

The liquid dispensing opening26is located on the top of an elongated and tapered upright mouthpiece66, seen best inFIGS. 1,3,4and6, which is generally oval in shape at the top. The mouthpiece extends upwardly to a flattened peak having an elliptical top68with a major axis70, seeFIG. 3, which intersects the circular opening26at the center of the top and also intersects the middle of the hinge22. The side mounted hinge22is coaxial with, and the cap20is movable about, a transverse axis72which is normal with the major axis70, i.e. is at a 90 degree angle. Extending downwardly from the elliptical top and located on opposite sides of the major axis70are wide and generally planar sides74which are adapted to contact the upper and lower lips of a user when drinking from the closure. A pair of narrow and arcuate sides76connect the wide sides74. The sides74and76taper towards the oval top rim68. The upright, elongated and shaped mouthpiece66is adapted to receive the user's mouth so that the user's lips on the wide sides74will generally seal the dispensing opening and prevent spills. The generally oval shape also provides tactile orientation and feedback to a user to better orient the mouthpiece within the user's lips during use.

It is also desirable to orient the cap20to open in a manner to avoid interference with the user's face during use. The hinge22is to the side of the main lip contacting surfaces74and intersects the elongated main axis70. As a result, the cap20when flipped open as seen inFIGS. 4 and 6will be located away from and to a side of the user's nose, when the user's upper and lower lips are placed on the wide sides74of the shaped mouthpiece66.

To assist the user in flipping open the cap20by one hand operation, the base collar24has a thumb or finger grip recess80which forms a shallow depression or recess in the annular collar24, see particularlyFIGS. 5 and 6. A corresponding guide recess or indented surface82form shallow depression in the cap20and is aligned with and located above the thumb recess80. The aligned thumb recess80and guide recess82provide a visual indicator of where the user should place his or her thumb or finger on the closed cap in order to flip the cap upwardly to open the closure. The relieved surfaces80and82provide a convenient area for a user to push against and open the cap by a one hand operation while avoiding grip tabs or extensions which would protrude beyond the circular periphery of the collar. Standard capping equipment requires closures to be round when viewed from above, with no elements such as hinges or tabs or grips protruding from the periphery of the collar24.

Desirably, the thumb or finger recesses80and82are offset from the major axis70of the elongated mouthpiece66and are located along a skewed axis84, seeFIG. 3, which is at an acute angle86with respect to the major axis70. The acute angle should be at least 10 degrees and well less than 90 degrees, and preferably can be from 30 to 60 degrees. This offset is more desirable than providing a thumb recess80and guide recess82located on the major axis70, because users often will open the closure with their thumb while holding the closure directly in front of their face. As a result, a centrally located thumb recess would cause the cap20to flip directly backward so that the cap would be opposite the user's face and nose. By angling the recesses along an offset axis84, the cap20when flipped open is at an offset angle to the user's nose. This helps the user to correctly place his or her lips on the planar mouthpiece sides74, which also causes the opened cap20to be located properly to either side of the person's nose. While the offset axis84could be greater than illustrated inFIG. 3, too great an offset (such as 90 degrees) will place too much stress on the hinge22. Thus, the offset skewed angle86is a compromise to assist in orienting the cap to one side yet not staining the hinge too much with repeated openings.

The closure can include, if desired, a latch tab (not illustrated) on the cap20which mates with a stop or lock surface on the base closure24to prevent tampering prior to purchase. The latch and lock can be formed as a part of the recess surfaces80and82.

The mouthpiece66is hollow and forms a primary fluid passageway90, seeFIG. 7, which extends from the interior of the bottle40to the primary fluid dispensing aperture26. The bottom of the passageway90is formed by a divider baffle92having a skewed diagonal bottom edge94which angles from its lowest portion, adjacent the vent apertures60, to its highest portion adjacent the rear of the closure near the hinge22and hence furthest away from the vent apertures60. The collar24has an annular bottom wall96which forms the interior threads28for screwing the collar onto the container. The space between the divider baffle92and the collar bottom wall96forms a secondary fluid passageway100which conveys liquid from the container directly to the small diameter vent apertures60and passes venting air from the apertures60through the secondary passageway100and into the container. The divider baffle92forms an interior tube which surrounds the central fluid passageway90, and desirably extends into the container to its maximum length adjacent the vents60so as to better separate the air bubbles which flow through the vents60and into the container from the liquid being dispensed through the primary passageway90. The substantially open diagonal end94allows for a larger opening to the primary fluid passageway90, which reduces the velocity of the exiting liquid as it passes the baffle tube and thereby reduces entrainment of venting air into the liquid being dispensed.

The vent apertures60are located on and extend through a horizontal floor or shelf102, seeFIGS. 7 and 8, located at an intermediate position between the main opening26at the top of the mouthpiece66and the bottom of the closure. One vent aperture60is adjacent and to one side of the mouthpiece main axis70and the other vent aperture60is adjacent and to the other side of the mouthpiece main axis70, and both vent apertures are away from the hinge side. The base collar24includes an upper arcuate wall or skirt104which extends upwardly with the top edge being located above the vents60, so that the floor shelf102is recessed below the collar upper edge104. The curved extending skirt104forms a protective barrier and a channel for air passing into the vents60, and prevents the user's lips when contacting the mouthpiece from resting on and/or blocking the vent apertures60.

The base collar has a diagonal or skewed arcuate top edge106, seeFIG. 6, which slopes downwardly towards the hinge22. Similarly, the cap20has a arcuate bottom edge108extending along a diagonal slope which abuts the top edge106of the collar to seal the base collar24when closed and thus protect the liquid contents of the container from external contamination. The bias or diagonal line of parting at edges106and108, with the lowest point being adjacent the side hinge22, increases clearance of the cap with the user's face as compared with generally horizontal edges for the cap and collar, or a higher point adjacent the hinge, as is standard in many hinged closures. That is, the height of the collar wall is higher adjacent the vents60, and lower adjacent the hinge22, so the cap20can be flipped further away from the peak of the mouthpiece66. Desirably as seen inFIG. 6, the fully open cap20moves to a position which extends partly below the bottom of the collar24, and thus further increases clearance away from the top of the mouthpiece74. If desired, a safety seal (not illustrated) can encircle the cap20and collar24to protect the contents of a pre-filled beverage container40prior to purchase and initial use by a consumer.

The secondary fluid passageway100desirably includes structure to form a serpentine or turbulent pathway for the venting air entering the vents60. As seen inFIGS. 7 and 8, the secondary fluid passageway100is desirably formed asymmetrically to one side of the collar and away from the central main fluid passageway90. A barrier ring110is located in the direct path between the vents60and the secondary passageway100. The ring110is floating and is captured between a plurality of posts112which extend from the floor shelf102, and a rib116on the collar24. The edge of the floating ring110abuts a plurality of ribs114formed on a side wall extending from the floor102. The ring110is sized to allow venting air bubbles to be diverted to the side and around the ring and through the plurality of channels formed between the ribs114and then back into the secondary fluid passageway100. The ring110can be made of a semi-rigid material such as low density polyethylene, and can float within a narrow range of vertical movements between the posts112and a capturing rib116formed from a protrusion in the tube wall forming the divider baffle92. The resulting serpentine or wavy path around the ring110assists in minimizing the size of air bubbles flowing through the vents60and into the secondary passageway100. The smaller air bubbles which result help to reduce undesirable bubbling noise as the user tilts the container and draws liquid out the main bore26in order to dispense the liquid. Thus, the secondary fluid passageway100desirably has a wavy or circuitous path for venting air, or otherwise creates a non-straight path for venting air which is forced to travel at a substantial angle to the otherwise longitudinal flow of liquid through the primary fluid passageway90in order to quiet the sound of air bubbles entering the container when titled to dispense liquid. The use of multiple vent apertures60, each of small size, also assists in producing small air bubbles in the secondary fluid passageway100.

FIG. 9shows test apparatus used to determine the relationships regarding one or more of the vent apertures60and the main fluid dispersing opening26, labeled A in the test apparatus. A tubular container120of PVC plastic having rigid sides was constructed of a height H and an internal diameter W, and was sealed at both ends. A liquid dispensing bore26was drilled of various diameters A. One or more vent apertures60, having a diameter D, were drilled into the plastic tube at various heights which correspond to a dimension C, i.e., the offset distance between the liquid dispensing opening A and the top of the vent aperture D. Also, the vent aperture D was formed with several different diameters.

In one set of tests, the container had a height H of approximately 10 inches and a diameter W of approximately 1 inch. A total of sixteen small diameter vent apertures D were drilled, each at 0.100 inch spacing from the bottom end of the container. To provide sufficient distance between each test aperture, the sixteen vent apertures were located along a spiral path around the external diameter of the tube so that each vent diameter could be drilled to a larger diameter. The vent holes initially were all of the same 0.025 inch diameter. All sixteen holes were covered to form an airtight seal. The container ofFIG. 9was filled with water. The apparatus was oriented with the dispensing opening A at the bottom as illustrated inFIG. 9. No liquid was then being dispensed through the opening A. Next, each vent D was exposed one at a time from the bottom up. As the first fifteen vents were exposed to air, no liquid escaped through the dispensing bore A which remained self-sealing by surface tension. When the sixteenth vent was uncovered at a vertical height of about 1.6 inch, venting air began to flow into the interior of the sealed container and water was dispensed through the dispensing bore A. Thus, above a maximum value for C, the vent aperture D would allow air bubbles to flow into the container so that the container became a pouring-type container which no longer would self-seal by surface tension of liquid.

In other tests, the container had a height H of 8.25 inches and a diameter W of 1.0 inch. The dispensing opening had a diameter A of 0.125 inches for one set of tests, and 0.250 inches for another set of tests, and 0.315 inches for further tests. It was determined that the fluid dispensing opening can be varied in diameter A within a range without affecting the self-sealing feature. However, once the diameter A is greater than approximately 0.4 inches, the fluid opening A will self-vent and admit air through the opening A itself. Thus, the primary liquid dispensing opening A preferably should be less than about 0.4 inches in diameter, or less than an equivalent cross-sectional area if the liquid dispensing opening A is irregular in shape.

The term equilibrium means that a flow of liquid will stop in a short time, such as less than one second, after an external disabling force is removed. The term non-pour means that when a container is inverted, with the vent aperture obstructed and also with the vent aperture open, the same amount of liquid will escape the closure before it reaches a static state.

FIG. 10is a graph which plots the results of several experiments and also illustrates the relationship between the offset C and the diameter D for these experiments. A vertical axis labeled Offset C represents the offset height in inches from the liquid dispensing bore A to the top of the venting aperture D inFIG. 9. A horizontal axis represents the Diameter D in inches of various vent apertures. Each of the dots122represent a point of transition between a self-sealing closure versus a flow/pouring type closure for a particular liquid and closure material. For example, point122ashows that a vent aperture D of diameter 0.05 inches was self-sealing by surface tension when located in a desired range from 0 to about 0.82 inches above the liquid dispensing aperture A. When this same vent diameter of 0.05 inches was located by an amount greater than 0.82 inches above the liquid dispensing aperture A, then venting air would enter through the vent aperture D and liquid would flow out of the dispensing opening A. As another example, point122bshows that a vent aperture D of diameter 0.10 inches was self-sealing by surface tension when located in a desired range from 0 to about 0.48 inches above the liquid dispensing aperture A. Two overlapping dots122bare illustrated which represent two different experiments in which the results were essentially the same for water at room temperature. When the vent aperture of diameter 0.10 inches had an offset C greater than about 0.48 inches, the liquid surface tension would rupture and air would undesirably flow through aperture D causing liquid to flow through aperture A.

The points122inFIG. 10, which represent the points of transition between a self-sealing closure and a pour closure, are also summarized below in the following Table A. In this Table A, the offset C listed thus represents the maximum length possible to maintain self-sealing by surface tension for each listed vent diameter.

Liquid1is water at room temperature, and the resulting plots for dimensions C and D are shown inFIG. 10by dots122. Liquid2is water with a soap surfactant added to reduce surface tension, and the resulting plots are shown by star symbols124inFIG. 10. The weight of soapy liquid which could be supported was reduced by about half or more due to a reduction in surface tension. All dimensions in Table A are given in inches and have been rounded off to the nearest 0.01 inch.

When the different test points for liquid1in Table A are plotted, the resulting dots122form a curve130seen inFIG. 10, which starts somewhat linear for small diameters D and becomes more arcuate for larger diameters D. All intersections above the curve130are labeled “flow” because vent apertures of corresponding diameter D and offset C would allow air to continuously bubble through the venting apertures D and cause liquid to flow from the dispensing aperture A. Such a combination effectively creates a pouring dispenser. All intersections below the curve130are labeled “self-seal” because vent apertures of corresponding diameter D and offset C would allow the vent apertures D and liquid dispensing aperture A to self-seal by surface tension while the container was at equilibrium. Thus, the many combinations of vent diameters D and offset amounts C located below curve130in the “self-seal” region represent the ranges of dimensions to be used to create the novel vented closures of the present invention.

For containers designed to hold other liquids, a plot can be made of test points to produce a curve similar to curve130in order to establish the desired combination of vent diameters D and maximum offsets C to create apertures D and A which will self-seal by surface tension for the specific liquid to be stored in the container. Thus, the placement and size of the vent apertures in the base collar can be empirically determined for the liquid to be dispensed. As vent apertures D are moved further away from the dispensing bore A, the diameter or cross-sectional area of each vent aperture must be decreased in order to maintain a self-sealing relationship using the surface tension of the liquid in the container.

The dispensing aperture A and the vent apertures D can have shapes other than circular. The dispensing aperture A can be of irregular shape which can form words and/or symbols. While the vent apertures D can be shapes other than circular, due to their small size, a circular bore is generally easiest to form and manufacture.

To allow for manufacturing tolerances and material variations, it is preferable to select dimensions which are spaced away from the transitional curve130which is the dividing line between self-sealing closure and a flow closure. For example, a diamond point132is spaced sufficiently away from the transition curve130by a desirable amount to self-seal and take into account tolerances and variations which can occur. Thus, the dimensions can be varied provided they plot within the self-seal regions ofFIG. 10. For example, it has been found preferable considering human factors and a closure which is within typical commercial standard sizes for the offset height C to be within a predetermined range from about 0.4 to 0.9 inches. Furthermore, a desirable range for the vent diameters is less than 0.10 inches, and preferably from 0.09 to 0.03 inches or an equivalent cross sectional area. Other ranges can be determined following the methodology set forth above. Thus, the relationship which creates the self-sealing action of the vent apertures60by surface tension is dependent upon the above considerations. Any closure should be made using dimensions which conform to and create vent openings which self seal by surface tension of the liquid in the container40.

FIGS. 11A,11B, and11C illustrate the operation of the present closure under different conditions. InFIG. 11A, the container42is tilted and squeezed along direction44to cause liquid to flow along the dashed lines140and exit the main liquid dispensing opening26. When the squeezing ceases, the liquid flow ceases in a short period and flow through the main opening26and vent openings60will cease as illustrated inFIG. 11B.

When the closure and container are tilted as shown inFIG. 11B, the effective column height of liquid between vent aperture60and dispensing aperture26increases. The offset C shown inFIG. 11Brepresents the distance or height between the top of the vent aperture60when in contact with fluid in the secondary fluid passageway and the bottom of the primary fluid passageway opening26. Offset C represents the hypotenuse of a triangle having a fixed dimension as one side with a variable dimension C being dependent on the angle of tilt of the closure and container. An additional column of liquid is above the vent aperture60, as well as above the dispensing aperture26, but is supported by a partial vacuum at the upper portion of the tilted container. When formed to be self-sealing following the teachings explained earlier, the potential energy of the liquid column C with a diameter of D is insufficient to overcome the coefficient of surface tension which seals the vent opening60. Thus, when at equilibrium as illustrated inFIG. 11B, liquid within the tilted container does not escape through the primary dispensing aperture26which is retained by a pressure differential, nor does equalizing air enter through the vent aperture60which is self-sealed by surface tension.

As a pressure differential is created by a user placing his or her mouth over the mouthpiece66and sucking to create a vacuum, liquid in the tilted container will flow in a squirt or burst through the primary fluid passageway and along the direction of the dashed line/arrow140inFIG. 11C. At the same time, venting air will pass along the dashed lines142from outside the cap, through the vent apertures60and into the secondary liquid passageway. The resulting air bubbles, which are not to scale, will travel through the liquid in the secondary fluid passageway and into the container to vent the container to external air.

Liquid will continue to be dispersed from the container and venting air will continue to flow into the container as seen inFIG. 11Cuntil the external destabilizing force (sucking on the mouthpiece or squeezing the bottle) ceases. After a short time such as one second or so after removal of the destabilizing force, equilibrium will be established and conditions will return to the steady state condition illustrated inFIG. 11B. That is, the surface tension of liquid will self-seal the vent apertures60, and the liquid in the container will be retained by a pressure differential after a small amount of liquid passes through opening26without being equalized by venting air. Thus, the passage of liquid and air through the apertures will cease even though those apertures remain open. To overcome this equilibrium or steady state condition, the user needs to again create an external destabilizing force which overcomes the surface tension of liquid at the aperture60and the pressure differential at the opening26.

As the offset length C increases, the cross-sectional area of the vent openings60must decrease in order to maintain self-sealing by surface tension of the liquid. The vent apertures60could be located, for example, on a surface further from the main opening26, but this requires a very small diameter vent aperture60in order to maintain a self-sealing relationship. A very small diameter opening is more apt to be blocked by dust, dirt and other conditions. Conversely, the vent apertures60could be located on a surface closer to the main opening26but this would increase the likelihood of the vents being covered by the users lips. The location illustrated in the drawings provides a good balance between the size and location of the air vent60while maintaining the desired self-sealing properties.

The present invention has been described in an illustrative manner. It should be understood that modifications may be made to the specific embodiments shown herein without departing the spirit and scope of the present invention. Such modifications are considered to be within the scope of the present invention.