Any inventor should conduct a free patent search in order to determine the patentability of his or her invention. Patent searches have traditionally been limited to a search of the Patent Office’s records of prior patents and publications. The recognition of business method patents combined with the assistance of the Internet made it both necessary and possible for patent searches to evolve and become easier to do. Still, patent searches begin in the electronic databases of the various Patent Offices worldwide.Inventors don’t necessarily need the help of a professional to conduct a prior patent search. They can do the work themselves by searching for patent search Web sites online. For an inventor to be able to start his or her own patent search, he or she needs to first access the U.S. Patent Office Database at

A Patent and Trademark Depository Library (PTDL) is a library designated by the (PTO) to receive and house copies of US patents and patent and trademark materials, to make them available to the public, and to disseminate both patent and trademark information. A library must meet specific requirements and promise to fulfill certain obligations to be designated as a PTDL. At these PTDLs patents and trademarks (word marks only) may be searched. Patent and Trademark Depository Librarians cannot give any legal advice nor can they perform the free patent search for someone.

For many inventors it is important to avoid spending thousands of dollars in a patent application only to have it refused. In some instances, only certain elements of the proposed invention (embodiments), but not all, will be patentable. Conducting a prior patent search and allows the inventor to identify the patentable elements and file a patent application which avoids the problem embodiments.

7 steps to conducting a free patent search at Patent and Trademark Depository Library (PTDL):

1. Index to the U.S. Patent Classification
Begin with this alphabetical subject index to the Manual of Classification. Look for common terms describing the invention and its function, effect, end-product, structure, and use. Note class and subclass numbers.

2. Manual of Classification
Locate class and subclass numbers in the Manual. Note where the terms fall within the US Patent Classification System. Scan the entire class schedule, paying attention to the dot indent. Revise search strategy as needed.

3. Classification Definitions
Read the definitions to establish the scope of class(es) and subclass(es) relevant to the search. The definitions include important search notes and suggestions for further searching.

4. Browse Patent Titles and Abstracts
Check if you are on the right path; retrieve and browse through titles of patents and published applications in the given class and subclass. Or redirect the search: retrieve lists of patents and published applications containing applicable keywords; note their class and subclass numbers and go back to Step 2. Remember that Patents BIB includes bibliographic information for patents from 1969 to present and published patent applications from 2001 to the present. WEST includes the full-text of patents from 1971 to the present. USPTO databases on the Web include the full-text of patents from 1976 and images (searchable only by class or number) from 1790 to the current week, plus published applications from 2001 to present.

5. Retrieve Subclass Listing
Once you have identified the relevant classes and subclasses, obtain a list of all patent numbers granted from 1790 to the present and all published applications from 2001 to the present for every class and subclass to be searched.

6. Official Gazette – Patent Section
Go to the Gazette and look for exemplary claim(s) and a representative drawing for all patents on the list(s) to eliminate patents unrelated to the invention. For published applications, view the complete document on-line.

7. Complete Patent Document
Search the complete text and drawing(s) of closely related patents to determine how different they are from the invention. (Years of coverage vary with format).