1.  Field of the Invention
The present invention relates to a filter, specifically, a filter that is designed for gravity-fed applications, having filter media with hollow center, the filter being generally prone to a degradation or cessation in fluid flow due to air entrapment or air lock within the filter housing cavity, which develops during filtering.  A diffuser element or surface tension disrupter is introduced to the filter housing in order to pierce the entrapped air bubble, and prevent air lock from occurring during filtering by dispersing an otherwise large air bubble blockage, and allowing fluid to flow through the smaller entrapped air bubbles. 
2.  Description of Related Art
The presence of unwanted and potentially harmful contaminants in drinking water is a cause for health concern.  This concern causes a desire for water treatment devices suitable for use in the home and as portable instruments for water treatment.  Several types of gravity-flow filtration systems have been developed to address various health concerns. 
A common application of the instant invention is directed to a batch treatment and filtration device where water is filtered, treated, and stored in a container.  The treated water is poured from a spigot of the water container which functions as a self-contained water treatment system.  These self-contained systems typically have upper and lower chambers separated by a filter cartridge.  The most popular styles being the pour-through carafe or the refrigerator water tank.  Such systems include an upper reservoir for receiving unfiltered water, a lower reservoir for receiving and storing filtered water, and a filter, usually of granular activated carbon or pleated fiber sheets, with at least one inlet at the filter housing top and at least one outlet at the filter housing bottom, which allows water to flow from the upper reservoir to the lower reservoir.  The pour-through carafe is sized to be handheld, holds about one-half gallon of water, and may be tipped for pouring filtered water, as in a conventional pitcher or carafe. 
Gravity flow carafe filters have been commercially available for several years and their popularity with consumers continues to grow.  Currently available commercial water carafes are capable of removing lead using an ion exchange resin, undesirable tastes and odors using carbon granules, and large particles using a packed bed configuration. 
The refrigerator tank system is typically a larger rectangular tank with a spigot for draining filtered water into a glass or pan.  Both the carafe or tank designs use gravity to cause the unfiltered water in the top reservoir to flow down through the filter cartridge and into the lower reservoir where the filtered water remains until it is used. 
Filter media used for these types of applications is generally cylindrical in shape with a hollow center for fluid flow.  The introduction of the unfiltered fluid through the filter media is known to entrap air between the hollow center and the housing top cap, forming a large air bubble.  This air bubble prevents fluid from entering the core and displacing the air, resulting in what may be generally referred to as a “vapor lock” or “air lock” condition, which degrades or ceases fluid flow. 
In the prior art, care is taken to maintain a fully primed condition, i.e., preventing air access to the primed filter.  Allowing air access allows blocking air inclusions removed during priming to re-form in the filter pore structure, significantly reducing flow until the primed condition is re-established.  The advantage of maintaining the prime extends to essentially any micro-porous filter medium regardless of composition, including ceramic, carbon, or polymer membranes or filter bodies of inorganic or organic composition.  However, this technique requires the filter media to remain constantly and completely submerged in water, so that air inclusions in the filter cannot re-form. 
The present invention is designed to mitigate air lock upon introduction of unfiltered water into the filter media even when not fully submerged.