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Mechanical Engineering Home >Info: Useful Links > Patent > Searching

W. Durfee 1/17/95

The Minneapolis Public Library in downtown Minneapolis is an official "PatentDepository Library" which means it contains a complete file of U.S. patents from 1790 to the present. It is the only Patent Depository Library in the state of Minnesota and is the best (although not necessarily the most convenient) way to conduct a do-it-yourself patent search.

The library is located at 300 Nicollet Mall (corner of Nicollet and 4th Street)in downtown Minneapolis. From the U of M, get there by car and park in one of the nearby lots or ramps (approximate parking cost is $1.50 per hour), or take a Number 6 bus from the corner of 4th Street and 15th Av in Dinkytown and get off at Hennepin and 3rd or 4th Street. The library is 2 blocks west. Bus fare is $1.00 each way and $1.50 during rush hours. Buses are exact fare, but will accept bills.

Library hours are Monday-Thursday 9:00 am to 9:00 pm, Friday 9:00 am to 5:30 pm, Saturday 10:00 am to 5:30 pm, and closed on Sunday and holidays.

Once you have passed through the entrance turnstiles of the library, go right towards the "Business and Economics" section, then left towards "Government Documents". The patent collection is a little ways down on your right. The major components of the collection include (1) file drawers with microfilm reels containing all of the U.S. patents, (2) several microfilm readers, (3) a complete printed collection of the "Official Patent Gazettes", (4) various patent indexes, (5) a PC containing the CASSIS system, (6) various books on patents and patent applications. Note that there is only one CASSIS system PC and it has a time limit of 15 minutes, so you are advised to do your searches when the library is least crowded.

If you have any questions on how to use the patent resources, consult a reference librarian at the "Government Documents" desk just around the corner, or you can call the Government Documents department at 372-6534 with questions. Note that the library gives "How to Do a Patent Search" talks every other Friday 11:15 am to 12:15 pm. Call the Government Documents department for dates.

Follow the directions provided in the brochure "Down & Dirty Patent Searching", available at the library. An important component of the search is using the CD-ROM based Classification and Search Support Information System (CASSIS). Its operation is reasonably self explanatory if you pay attention to the on-screen dialog, or you can consult the CASSIS manual located near the PC. You will find two parts of the CASSIS system to be of most value. Use CASSIS/CLASS to determine all patent numbers (1790 to present) which fall under a particular class/subclass. Use CASSIS/BIB to search patent titles by word or term or to search on inventor names and get back patent title and number information (1969 to present).

Warning: A comprehensive patent search can take considerable time. Allow 4 hours for a cursory search and 10-50 hours for a comprehensive search. After you find the proper set of classes and subclasses (or what you think is the proper set), CASSIS/CLASS will provide you with many, many patent numbers. Looking up the full patent by its number to determine whether it is what you are looking for is a tedious process since you have to find the right microfilm reel, load it on the reader, scroll to the proper number then skim the patent. This is why companies and patent attorneys subscribe to an on-line, full-text search service and pay their $4 per connect minute.

If you are looking up patents whose numbers are greater than 2,966,680 (January 1961), it can be faster to do your quick scanning using the printed version of the Official Patent Gazette. Although you only get the abstract and a picture, generally it should be enough, or certainly enough to determine whether it is worth reading and/or copying the full version of the patent using the microfilm reader.