PATENT SEARCH LINKS
www.google.com/patents Google Patents covers the entire collection of granted patents and published patent applications from the USPTO (United States Patent and Trademark Office) and the EPO (European Patent Office) . US patent documents date back to 1790, EPO to 1978.
http://patft.uspto.gov/ (United States Patent and Trademark Office) The USPTO houses full text for patents issued from 1976 to the present and TIFF images for all patents from 1790 to the present.
http://www.epo.org/searching/free/espacenet.html (European Patent Office) Espacenet offers free access to more than 70 million patent documents worldwide, containing information about inventions and technical developments from 1836 to today.
http://patentscope.wipo.int/search/en/search.jsf (The World Intellectual Property Organization) Using PATENTSCOPE you can search 18,761,269 patent documents including 2,204,788 published international patent applications (PCT)