There are three main steps to a subject search to determine if an idea has already been patented:

1. identifying the class and subclass numbers that fit the subject matter of your invention.
2. obtaining the list of the patent numbers issued to each of those classification designations.
3. examining every patent on each of those lists to see if one of them is your idea.

If the correct classification designations for your invention have been selected and there are no conflicting patents on any of the lists, a patent for that invention has not been issued in the United States.

1. Consult the Index to the U.S. Patent Classification.

Index to the U.S. Patent Classification.
LOCATION: Morris Library - Reference (Ref T223 .A25) Shelved in the Patent Alcove
LOCATION: Internet (http://www.uspto.gov/web/patents/classification/uspcindex/indextouspc.htm) via the USPTO web site
LOCATION: Morris Library - Reference via the CASSIS ASSIST files

The Index, used to access the Manual of Classification, is an alphabetical listing of subjects contained in the Manual. Select a word which best describes the subject of the invention, e.g. bicycle seat. The Index will list one (or more) relevant class and subclass numbers. If there is more then one class or subclass listed for the subject, choose the one that best represents the subject matter of interest. The main heading "Bicycle" in the Index has many subheadings, one of which, "Seat," refers the user to class 297, subclass 195.1+. Remember that a plus (+) sign next to the subclass indicates that there are other subclasses listed under 297/195.1 in the schedule that need to be examined.

If no obvious entry for the idea was found in the Index, try a keyword search of the inventions subject terms in the TITLE OR ABSTRACT field of the PATENTS BIBLIOGRAPHIC INFORMATION file on CASSIS. This will retrieve all of the patent records in that file that contain those words in the title or abstract and it can be assumed that some of these patents will be similar to the idea being investigated. Browse the titles that the search retrieves and look for one that appears to be similar to the subject matter of interest. Display the full record of that title and observe which class the original classification (the first one listed) is assigned to. Look up the title of that class in the Manual and decide if it is the right class for the invention under consideration. If so, start your search in that class. If not, keep looking at other similar patents until you determine the right class.

2. Turn to that class/subclass in the Manual of Classification.

   Manual of Classification.
   LOCATION: Morris Library - Reference (Ref T223 .F4 U5a) Shelved in the Patent Alcove
   LOCATION: Internet (http://www.uspto.gov/go/classification/index.htm) via the USPTO web site
   LOCATION: Morris Library - Reference via the CASSIS ASSIST files

   The Manual is the complete listing of classes and their subclasses, arranged by class number in ascending order. If the Index provided both a class and subclass number, turn to that class and begin the search at the subclass provided. If the Index provided only a class number, start with the first mainline subclass (in capital letters) in the selected class and proceed from one mainline subclass to the next until one is located that includes the subject matter of the invention. Then, starting with the one dot subclasses, examine the schedule of subclasses beneath that mainline subclass (assuming there are some) for the appropriate subclasses for the invention. In some cases, the numbers provided by the Index will be the only ones needed, but this is very rare. In most cases, a scan of the Manual will indicate more specific class/subclass numbers for the invention. Remember to always pay attention to the scheduled order of the subclasses.

3. If the definition of a class or subclass is required, consult the Patent Classification Definitions.

   Patent Classification Definitions.
   LOCATION: Morris Library - Reference (MFiche S260) Shelved in Patent Alcove
   LOCATION: Internet (http://www.uspto.gov/go/classification/index.htm) via the USPTO web site
   LOCATION: Morris Library - Reference via the CASSIS ASSIST files

   This file provides detailed definitions of each class and subclass, contains references to other classes and subclasses when appropriate, and lists the distinctions between certain classes. Remember, the Manual classifies things by what they do, not what they are used for, so often the appropriate subclass might not seem obvious at first glance (e.g. a bicycle seat is included under the first level subclass "Straddle Seat") so always check the definition if you are not sure how the Manual defines the subclass.

Repeat these first three steps until the classification numbers that fit the subject matter of the invention have been obtained.

4. Determine which of these classification designations will need to be examined in their entirety.

   It isn't always necessary to fully examine each of the classification designations selected if it can be determined that some of these classifications are identifying aspects of the invention that aren't central with its primary function. By examining patents in the Bibliographic Information File that have already been issued to the selected classifications the user can determine which of these classifications need to be examined in their entirety and which can be eliminated as extraneous to the substantial aspects of the invention.

   To see brief information on patents that have been issued with the classifications under consideration search the PATENTS BIBLIOGRAPHIC INFORMATION file by those class/subclass numbers. Search each classification separately and browse through the retrieved records. The patent records in this file will all have titles, and those issued in the last three years will also contain a brief abstract about the patent. By examining these records the searcher will be able to determine which classification numbers need to examined in their entirety.

   Important: The complete patents are not available in this file and no patents issued prior to 1969 are in this file.

5. Search each of those classification numbers.

   Patent Classification Information - by Subclass
   LOCATION: Internet (http://patft.uspto.gov/netahtml/search-bool.html) via the USPTO web site
   LOCATION: Morris Library - Reference via the CASSIS ASSIST files

   This will retrieve a list of the numbers of every patent issued with each of those classifications from 1790 to the present. Print each list of patent numbers so the lists can be used to locate the patents for examination. Examine the patents designated with an original classification, indicated by a "O" to the right of the patent number, first. If no conflicting patents are found in the original designations, then examine the cross reference designations, indicated by an "X" to the right of the number. Remember, every patent issued with the classification under consideration must be examined in order to complete a patent search.

   Patent Full-Text and Full-Page Image Database.
   LOCATION: Internet (http://www.uspto.gov/patft/index.html) via the USPTO web site
   

   In the US PTO patents search, type the class/subclass in the search box and limit to the field "Current US Classification". Note: type the class number/subclass number, with no spaces.

6. View brief informaton of the patents you have listed.

   Official Gazette of the United States Patent and Trademark Office: Patents.
   LOCATION: Morris Library - U.S. Documents (U.S. Docs C 21.5:)
   LOCATION: Internet (http://www.uspto.gov/web/offices/com/sol/og/index.html) via the USPTO web site

   The Official Gazette is published weekly and lists the patents in numerical order from 1872 to the present. It provides a brief summary about the patent and includes the primary drawing. This is the best source for the initial examination of the patents. If the record in the Official Gazette doesn't provide sufficient detail of the patent, then use the microfilm copy of the complete patent. There is no need to view the complete patent unless the OG doesn't provide enough detail. Prior to 1872, use the Patent Office Report (title varies) at U.S Doc C21.1/2 or go to the complete patent.

   The online version of the OG includes 1995 to present.

   Patent Full-Text and Full-Page Image Database.
   LOCATION: Internet (http://www.uspto.gov/patft/index.html) via the USPTO web site

   Contains brief description and abstract of patents from 1976 to present.

7. View the complete patent.

   Patents Collection.
   LOCATION: Morris Library - Microforms (Lower Level)

   One collection is in order by patent number and is on 16 mm microfilm. Another collection is in DVD format.

   Patent Full-Text and Full-Page Image Database.
   LOCATION: Internet (http://www.uspto.gov/patft/index.html) via the USPTO web site

   Contains complete patents (full image) granted since 1790. Images are in a graphic format called Tiff. A special tiff viewer is needed. See the "Help" pages on the PTO web site for more information.

For Further Assistance

If there is a problem in determining the correct classification for the idea, or if there are other questions, contact the Patent Librarian for further assistance.

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