Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
2000-07-07
2001-07-24
Carrillo, Sharidan (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C134S001300, C134S002000, C134S010000, C134S013000, C134S032000, C134S034000, C134S035000, C134S040000, C134S198000, C134S199000, C134S200000, C134S902000, C210S748080
Reexamination Certificate
active
06264753
ABSTRACT:
BACKGROUND
The present invention relates generally to low temperature liquid carbon dioxide cleaning systems and methods, enhanced by vigorous agitation methods, to displace insoluble soils off surfaces, emulsify, disperse and suspend these soils in a liquid carbon dioxide medium for transport and removal.
All cleaning and degreasing solvents currently used present health risks and are environmentally detrimental. For example, perchloroethylene is a suspected carcinogen, petroleum based solvents are flammable and smog producing, 1, 1, 1-trichloroethylene is known to deplete the earth's ozone layer and is scheduled for phase-out.
Liquid carbon dioxide is an inexpensive and unlimited natural resource, that is non-toxic, non-flammable, non-smog-producing or ozone-depleting. Liquid carbon dioxide does not damage fabrics, or dissolve common dyes, and exhibits solvating properties typical of hydrocarbon solvents. Its properties make it a good dry cleaning medium for fabrics and garments and industrial rags, as well as a good degreasing solvent for the removal of common oils and greases used in industrial processes, and a good liquid medium for insoluble soil suspension, dispersion and transport.
One disadvantage of the liquid carbon dioxide as a degreasing solvent is its reduced solvating capability compared to the common degreasing solvents. This deficiency has usually been addressed by the use of chemical additives or co-solvents. These additives increase the cost of operation and must be separated out for disposal, as part of solvent reclamation processing, further increasing operating costs.
Accordingly, it is an objective of the present invention to provide for a liquid carbon dioxide cleaning system and method at low temperatures, enhanced by vigorous mechanical agitation methods to displace, suspend, emulsify and transport the soil away from the substrates to be cleaned.
SUMMARY OF THE INVENTION
To accomplish the above and other objectives, the present invention provides for an improved liquid carbon dioxide cleaning method that comprises jet edge sonic generators as a means of ultrasonically emulsifying and dispersing insoluble solids, and non-miscible liquids in liquid carbon dioxide used in the cleaning system. Agitation via sonic generators is presented as an example, and the present invention does not exclude the use of other high-energy agitation methods at low temperature, such as those generated via using transducers or cavitating blades, propellers, impellers, or nozzles, for example.
The use of the jet edge sonic generators may be used along with other cleaning techniques and the cleaning process can be performed at low processing temperatures. Typically, cleaning is performed at temperatures between −68° F. and 32° F. The present invention is particularly relevant to processes that utilize liquid carbon dioxide as a degreasing or cleaning solvent or as liquid suspension and dispersion medium.
The present invention reduces the cost of the liquid carbon dioxide degreasing system and process described in U.S. Pat. Nos. 5,339,844 and 5,316,591, respectively, which are assigned to the assignee of the present invention. These savings are due to cost reductions through the physically enhanced transport capacity of the liquid carbon dioxide.
The present invention addresses the replacement of conventional cleaning fluids with liquid carbon dioxide. It also addresses liquid carbon dioxide degreasing of common machined parts or bio-burden removal off of medical devices, prior to sterilization. The present invention improves the mass transport potential of the liquid carbon dioxide by sono-hydrodynamic agitation and other vigorous agitation methods, minimizing the need for solvent enhancing additives.
Because of the enhanced cleaning capabilities of sono-hydrodynamic agitation, effective cleaning is carried out in a low temperature environment, with liquid carbon dioxide temperatures below 32° F. (0° C.). This is particularly useful in the medical field where the moisture containing bio-burden is frozen by the low process temperatures and then displaced by agitation. Because the operating temperature of the present cleaning system is lower than that described previously, the system operating pressure is lower. This lower pressure results in more economical system manufacturing and operation, while maintaining a cleaning level achieved at higher liquid carbon dioxide temperatures and associated higher pressures.
REFERENCES:
patent: 4491484 (1985-01-01), Williams
patent: 5467492 (1995-11-01), Chao et al.
patent: 5858107 (1999-01-01), Chao et al.
patent: 5996155 (1999-12-01), Chao et al.
patent: 6004400 (1999-12-01), Bishop et al.
Chao Sidney C.
Purer Edna M.
Sorbo Nelson W.
Alkov Leonard A.
Carrillo Sharidan
Lenze, Jr. Glenn H.
Raufer Colin M.
Raytheon Company
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