Liquid purification or separation – With means to add treating material
Reexamination Certificate
2001-10-03
2003-04-08
Lithgow, Thomas M. (Department: 1724)
Liquid purification or separation
With means to add treating material
C210S205000, C137S268000, C422S264000, C422S266000, C422S272000, C422S274000, C422S278000
Reexamination Certificate
active
06544414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to water-soluble chemical feeders where the chemical from the feeder is eroded by water so as to produce a sanitizing solution of dissolved chemical and water. In particular, the invention relates to an apparatus and method for reducing moisture in the atmosphere inside the storage hopper for a chemical tablet feeder.
2. Description of Prior Art
Water-soluble chemicals in water sanitizing devices (also known as “chlorinators”) have a problem with moisture in the storage chamber softening the chemical tablets in at least two uncontrolled ways. The first concerns condensation forming within the hopper. The second concerns a humid atmosphere within the hopper and the chemical tablets “wicking” of the water vapor from the air.
Since water or other dissolving liquids are used to erode chemical tablets of a water sanitizing unit, the atmosphere within the hopper or chamber that stores such tablets tends to be moist, and particularly when the ambient temperature outside the storage chamber is low, condensation can form on the interior walls of the chamber. Such condensation can soften tablets in the hopper in a non-controlled fashion.
In operation, a storage chamber does not fill completely with water, but rather water contacts only the bottom layer of tablets during the erosion process. When the system is not operating, the water drains from contact with the tablets into a collection reservoir and/or to a mixing chamber below the tablets. Even when water is not flowing through the water sanitizing unit, a residual amount of water remains within the mixing chamber that is below the level of tablets. It is this water that tends to evaporate and cause the atmosphere within the chamber to become water-laden, that is humid. Since the tablets are stored in a hopper above the mixing chamber in such an environment for several days, they tend to “wick” the moisture from the water-laden air within the chamber and slowly become softer from the absorption process. This “wicking” or softening of the tablet changes the rate at which the tablet erodes into solution when water is applied to the surface of the tablet during operation.
Feeders that are typically used to erode solid calcium hypochlorite or other disinfection chemicals such as bromines, dichlorisocyanurates and trichlorisocyanurates for the purpose of disinfecting water, must maintain substantially a constant level of dissolution in order to maintain the proper residual level of dissolved chemistry within the process stream. Tablets that have become soft or moisture saturated erode at varying rates, thereby making the control of proper chemical residuals difficult or even impossible. Even the slightest change in tablet consistency and erosion characteristics alters the stability of the final chemical solution from the feeder.
Another problem with this type of feeder is that the softening of the tablets can often cause the tablets to stick together or to the sides of the storage chamber. This process is commonly called “bridging”, because the tablets form a bridge that supports the remaining tablets above the bridged area, thereby preventing the tablets from moving by gravity into the lowest portion of the feeder as the erosion process continues. The lowest portion of the feeder is where the tablets are eroded by water flowing over them. When a “bridge” of tablets forms, and all the tablets below such a bridge have been eroded away, there is no longer any tablet being placed into solution and therefore the consistent delivery of the feeder is interrupted. Even the slightest interruption of output from the feeder can cause the residual chemical within the process to vary. In the case of public drinking water or in water used for swimming pools, these minor changes in chemical residual can cause a health hazard to people consuming or using the water.
Identification of Objects of the Invention
A primary object of the invention is to provide an apparatus and method for a chemical tablet water-sanitizing unit in which tablets or “pillows” or other solid geometric shapes erode at a consistent rate.
Another object of the invention is to provide an apparatus and method in a water-sanitizing unit that allows tablets to remain stable throughout the period in which they are stored awaiting the erosion process.
Another object of the invention is to provide a device which provides stability and consistency of the atmosphere and temperature within the storage or erosion container of a water-sanitizing unit.
SUMMARY OF THE INVENTION
The objects identified above, as well as other advantages and features are incorporated in a system that forces outside, ambient air through the inside of the tablet storage or erosion chamber of a typical tablet erosion feeder. In some cases, depending on the temperature of the outside ambient air, a heating element is provided to raise the temperature of the air being introduced to the chamber. The amount of air being introduced is extremely small, great enough only to maintain a positive pressure inside the chamber, causing the air inside the chamber to constantly flow through it to outside air. This constant movement of fresh outside air through the chemical tablets prevents condensation from forming within the chamber that is sufficient to degrade the tablets.
In most cases, simply balancing the air on the inside of the chamber with air from outside the chamber and maintaining that process with a slow but constant pressure is sufficient to prevent the formation of condensation within the chamber, and to lower the relative humidity inside the storage chamber, thus slowing or eliminating the “wicking” of moisture by the tablets. In cases where the outside air is very moist and cold such as during the winter months, a thermostat is used to measure the temperature of the fresh outside air being drawn into the system. When the temperature reaches a certain level, such as below 40° F., either a small light bulb or electrical heat strip or the like is activated that is sufficient to both dry the incoming air and raise the temperature of the air being delivered to the tablet storage or erosion area. This drying of the air and raising the temperature of air within the storage chamber inhibits if not completely eliminates formation of condensation within the storage chamber and reduces wicking of moisture from the air by the tablets. As a result, the physical structure of the chemical tablets is stabilized and bridging and sticking of the tablets to each other and the walls of the feeder is largely prevented.
REFERENCES:
patent: 5201339 (1993-04-01), Buchan et al.
patent: 5384102 (1995-01-01), Ferguson et al.
patent: 5743287 (1998-04-01), Rauchwerger
patent: 6138703 (2000-10-01), Ferguson et al.
patent: 6337024 (2002-01-01), Hammonds
Andrews & Kurth LLP
Bush Gary L.
Hammonds Technical Services Inc.
Lithgow Thomas M.
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