Patent classification systems are used to organize all inventions into similar groupings - putting like with like.
The USPTO created the USPC (United States Patent Classification) system over time to where it now contains approximately 450 classes and 150,000 subclasses.
Use the Index to U.S. Patent Classification (USPC) System to help find the correct patent classification.
Beginning 1 January 2015 the USPTO starting the process of switching over to using the CPC (Cooperative Patent Classification) system. This change is due in part to the globalization of patents and people wanting to search cross patent systems.
As U.S. patents work their way through the application and granting phases, both systems (USPC and CPC) should be searched.
Determining the classification of an invention is by far the hardest part of the patent search process.
To determine if an invention has been patented a thorough patent search should be conducted. This will entail searching a number of different patent websites, so it is wise to keep a journal of your work as to not duplicate efforts.
1. Brainstorm Keywords to describe your invention - think of synonyms.
2. Use Keywords to search for a similar match of your invention in Google Patents.
3. Note the class and subclass of the similar invention - either in USPC or CPC, or both.
5. Trace related patents through references.