OurÂ Green Off-Patent Report provides selected highlights of green patents which completed their 20-year term and expiredÂ within the lastÂ week or so (assuming the patentee paid all requisite maintenance fees; U.S. patents require payment of fees 3 1/2, 7 1/2, and 11 1/2 years after issuance to stay in force).
Many of the green technologies in use today are off-patent, i.e., the patents covering the technologies have run their 20-year term and expired.
Knowing which technologies are off-patentÂ is important because those technologies are in the public domain and can be exploited by anyone.Â It’s also interesting because it provides a window into what was cutting edge technology twenty years ago.
The green off-patent searching is performed by Cleantech PatentEdgeâ„¢.
U.S. Patent No. 5,354,477Â (Water Purification) entitled “Low Molecular Weight Amines and Amine Quaternaries for the Removal of Soluble Organics in Oil Field Produced Water.”Â The patent describes a method for removing hydrocarbons from water by injecting low molecular weight amines and preferably amine quaternaries with strong acids into an oil and water mixture to remove oil based salts.Â Filed April 7, 1992;Â issued October 11, 1994; expired April 7, 2012.
U.S. Patent No.Â 5,324,433Â (Soil/Water Restoration) entitled “In-situ Restoration of Contaminated Soils and Groundwater.”Â The patent describes a method for removing and stabilizing in-situ soluble heavy metal contaminants from soil and groundwater by injecting an aqueous solution of naturally occurring ions.Â The solution solubilizes the heavy metals into solution where they can be removed.Â Filed April 16, 1992; issued June 28, 1994; expired April 16, 2012.
U.S. Patent No. 5,261,970Â (Photovoltaic Cells) entitled “Optoelectronic and Photovoltaic Devices with Low-Reflective Surfaces.”Â The patent describes photovoltaic devices with low angle ‘V’ shaped grooves on the target surfaces.Â The grooves increase the efficiency of the devices by promoting internal reflection of light from the target surface at the interface of the coverglass.”Â Filed April 8, 1992; issued November 16, 1993; expired April 8, 2012.
U.S. Patent No. 5,260,588Â (LEDs) entitled “Light Emitting Diode.”Â The patent describes a light emitting diodeÂ formed as reverse mesas with mirrored sloping surfaces which reflect light in the direction of the light emitting diode surface, improving the efficiency of each diode.Â Filed April 14, 1992; issued November 9, 1993; expired April 14, 2012.
U.S. Patent No. 5,317,979Â (Greenhouse Gas Emissions Reduction) entitled “Method and Apparatus for the Complete, Dry Desulphurization of Combustion Waste Gases Comprising SO2 and Dust.”Â The patent describes a method for removing SO2 from the combustion waste gases of coal dust.Â The process includes heating the gas quickly to a temperature below the sintering temperature of the fly ash, then cooling the gas to a temperature where the distance between the temperature and the dew point is low and is below 25 degrees C.Â This binds the SO2 gas to the ash, cleaning it from the combustion waste gas.Â Filed April 16, 1992; issueed June 7, 1994; expired April 16, 2012.
David Gibbs is a contributor to Green Patent Blog.Â David is currently in his third and final year at Thomas Jefferson School of Law in San Diego.Â He received his undergraduate degree in Geology from the University of California, Berkeley.