Measuring and testing – With fluid pressure – Porosity or permeability
Reexamination Certificate
1999-02-16
2001-03-06
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Porosity or permeability
Reexamination Certificate
active
06196055
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for demonstrating the vapor permeability of paint or other types of surface coatings.
BACKGROUND OF THE INVENTION
Exterior and interior wall structures commonly are coated with a surface coating such as paint, sealer, textured coatings, stucco and so on. These surface coatings have various characteristics, including color, texture, moisture permeability and vapor permeability. It is desirable to have a surface coating that acts as a moisture barrier, but also allows the coated surface to breathe. This is because if the coating acts as a vapor barrier, this can lead to moisture build up, spotting, chipping, cracking, peeling, of the surface coating. Likewise, mildew can build up in the coated surface, and biological growth can occur, such as the growth of algae.
Resistance to moisture penetration, combined with vapor or gas permeability, is commonly viewed to be favorable characteristics of surface coatings. Accordingly there is a need to demonstrate or test these characteristics. For example, there is a need to demonstrate these characteristics to purchasers, users or consumers of surface coatings.
One apparatus for measuring vapor transmission rates is used in testing laboratories. Such an apparatus may use a cup or other enclosure with a permeable surface across an opening. The surface may be coated with the substance to be tested. Likewise a desiccant is placed inside the cup to absorb vapor. The cup is then placed in an environment with a known humidity level. As the desiccant in the interior of the cup absorbs moisture transmitted through the coated barrier, the cup can be weighed to determine the weight increase and therefore the vapor transmission rate.
This known apparatus suffers from various deficiencies for use as a demonstration or testing device. For example, it takes a relatively long period of time for moisture to transfer through the vapor barrier. Likewise, a measuring apparatus is required in order to determine the increase in weight of the cup as the desiccant absorbs moisture. Moreover, the transmission of the vapor or gas cannot easily be seen visually, or the liquid permeability is not readily observed. Without such visual demonstrability, the use of the known apparatus as a demonstration tool is somewhat limited.
Accordingly, there is a need for a demonstration and testing apparatus illustrating permeability characteristics of a surface coating.
SUMMARY OF THE INVENTION
The present invention alleviates to a great extent the disadvantages of the known apparatus and methods for demonstrating and testing the permeability of surface coatings by providing an apparatus that provides observable visual data, such as bubbles rising through water, as vapor or gas passes through the surface coating being demonstrated or tested.
In a preferred embodiment the apparatus of the present invention includes a pressurized gas or vapor supply providing the pressurized gas or vapor to a pressure chamber. On a side of the pressure chamber is a test block made of a relatively porous material. The test block is coated with the surface coating to be demonstrated, on at least a portion of its surface (and corresponding interstices). In one embodiment the test block is coated on all surfaces with a sealant, paint, textured coating, or other material to be tested. Alternatively a second coating may also be used. For example, the test block may be coated with a sealant and a textured exterior coating, similar to the way such products might be used on the outer walls of a building.
The block with the test coating is in communication with the interior of the pressure chamber, as well as unpressurized exterior. Preferably the test block is mounted in the top side of the pressure chamber and a liquid vessel is above the test block. In operation, the liquid vessel is filled with water or another suitable fluid. The portion of the test block exposed to the liquid vessel is in contact with the fluid. Before the pressure chamber, opposite the test block from the liquid vessel, is pressurized, if the coating of the test block is fluid resistant, then water is not observed seeping through to the pressure chamber (which may be unpressurized). Then, when the pressure chamber is pressurized, a pressure gradient is created, going from the pressurized pressure chamber, through the block, to the liquid vessel. When the pressure gradient is created, if the coating of the test block is vapor permeable, then vapor (or gas) can be observed as bubbles passing through the fluid, emanating from the test block. This is because a pressure gradient is created between the pressure chamber and the outside atmosphere through the test block.
In the preferred embodiment, the gas or vapor supply is in the form of a rubber ball that can be manually pumped in order to pressurize the interior of the pressure chamber to a higher pressure than the surrounding atmosphere. The liquid vessel is filled with water and then bubbles can be observed rising through the water, from the test block. This demonstrates the vapor permeability of the test block, and any surface coating applied to it.
These and other features and advantages of the present invention will be appreciated from review of the following detailed description of the invention, along with the accompanying figures in which like reference numerals refer to like parts throughout.
Baker & McKenzie
Politzer Jay L.
Textured Coatings of America, Inc.
Williams Hezron
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