Our Green Off-Patent Report provides highlights of selected green patents that have completed their 20-year terms and recently expired or will complete their terms and expire within the next week or so (assuming the patentee paid all requisite maintenance fees; U.S. patents require payment of fees 3.5, 7 .5, and 11.5 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-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.

The green off-patent searching is performed by Cleantech PatentEdgeâ„¢.

U.S. Patent No. 5,569,997, entitled “Power supply for volatile memory devices and portable electrical appliance in vehicles” and directed to an electrical power circuit for volatile electronic memory of electrical equipment in a vehicle wherein a rechargeable battery, a primary power source, and a power branch line coupled to the volatile memory continuously provide power to the volatile memory independently of an ignition switch.  Filed October 4, 1993; issued October 29, 1996; expires October 29, 2013. 

U.S. Patent No. 5,562,565, entitled “Power transmission system in a hybrid vehicle” and directed to a power transmission system including an automatic gear shift device comprising a speed change gear unit having an input element connected to the intermediate shaft and an output element connected to driving wheels and engagement means for effecting a predetermined speed change in the speed change gear unit.  Filed October 14, 1993; issued October 8, 1996; expired October 14, 2013.

U.S. Patent No. 5,548,504, entitled “Power line linking apparatus for linking a power generator to a commercial power line” and directed to a line linking apparatus comprising a DC power generator for generating power by solar cells, a pair of DC/AC converters connected to the DC power generator, and a wiring for interconnecting output terminals of the pair of DC/AC converters and terminals of a commercial power line in a single-phase, three-wire mode.  The apparatus achieves load balance and protection for loss of one phase in linking with a single-phase three-wire distribution.  Filed October 4, 1993; issued August 20, 1996; expired October 4, 2013.

U.S. Patent No. 5,495,908, entitled “Electric car control system” and directed to a control system for an electric car comprising a high voltage apparatus including an inverter for outputting a driving output for driving a motor based on power supplied thereto from a battery, a low voltage apparatus, and connection devices for connecting the high and low voltage units in such a relationship that a signal path is connected between the units as electrically isolated therefrom.  Filed October 5, 1993; issued March 5, 1996; expired October 5, 2013.

U.S. Patent No. 5,415,673, entitled “Energy efficient filtration of syngas cooling and scrubbing water” and directed to a process for the partial oxidation of a liquid hydrocarbonaceous fuel to produce a stream of cooled and cleaned synthesis gas, reducing gas, or fuel gas substantially free from entrained particulate matter and slag.  Filed October 15, 1993; issued May 16, 1995; expired October 15, 2013.

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