While we are seeing many exciting new developments every day in green technologies, one of the interesting features of the current cleantech boom is its reliance on mature technologies such as solar PV and wind, which went through prior periods of innovation in the 1970s and ’80s.
Thus, 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-patent is important because those technologies are in the public domain and can be exploited by anyone. It’s also interesting because it provides a window into what was cutting edge technology twenty years ago.
Thus, our Green Off-Patent Report provides selected highlights of green patents which completed their 20-year term and expired within the last 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).
The green off-patent searching is performed by Cleantech PatentEdge™.
U.S. Patent No. 5,340,998 (LEDs) – This patent is directed to LEDs having multiple GaAS and AlGaAs semiconductor layers. The invention facilitates higher speed turn-on and turn-off operations. The patent is entitled “Semiconductor surface light emitting and receiving heterojunction device.” Filed February 24, 1992, issued August 23, 1994, expired February 24, 2012.
U.S. Patent No. 5,248,346 (solar PV) – Entitled “Photovoltaic cell and array with inherent bypass diode,” this patent is directed to PV cell arrays and subarrays in which one type of cell has a single pn-junction and can function as both a current source and a bypass diode. The material bandgap energy level and n-dopant concentration of each cell is selected so that if a subarray is rendered inactive, current produced by the array will still flow through the subarray. Filed February 24, 1992; issued September 28, 1993; expired February 24, 2012.
U.S. Patent No. 5,276,381 (OLEDs) – This patent is entitled “Organic electroluminescent device” and directed to an organic electroluminescent device in which the emitting layer contains certain quinacridone and quinazoline compounds. Filed February 26, 1992; issued January 4, 1994; expired February 26, 2012.
U.S. Patent No. 5,272,108 (LEDs) – Entitled “Method of manufacturing gallium nitride semiconductor light-emitting device,” this patent is directed to methods of making LEDs having an N layer of n-type gallium nitride semiconductor, an I layer of semi-insulating gallium nitride semiconductor, a first electrode, a low-resistance region directly under the first electrode, and a second electrode isolated from the first electrode. Filed February 26, 1992; issued December 21, 1993; expired February 26, 2012.
U.S. Patent No. 5,252,409 (fuel cells) – This patent, entitled “Fuel cell,” is directed to a fuel cell having a three-layer plate assembly forming a system of continuous flow passages which serve as air feed passages and air exhaust passages. The invention provides easier and cheaper assembly while protecting the cell against damage due to thermal distortion. Filed February 26, 1992; issued October 12, 1993; expired February 26, 2012.
Eric Lane is a patent attorney at Luce, Forward, Hamilton & Scripps in San Diego and the author of Green Patent Blog. Mr. Lane can be reached at email@example.com.