The best place to start the process is by watching the USPTO tutorial. This is an excellent introduction to the search process.
The U.S. Patent Classification (USPC) was the USPTO system for over 100 years. Recently, however, a new classification system, Cooperative Patent Classification (CPC), co-developed with the European Patent Office (EPO). replaced the USPC for utility patents. (USPC will remain in use for U.S. design and plant patents.) For more complete information please click here to go to the CPC web page.
A preliminary U.S. Patent search is ideally a classification search of granted U.S. patents and published applications (prior art) conducted to determine patentability (novelty) of an invention. It can be supplemented with a keyword search. (From the USPTO tutorial)
Before you begin your search we recommend you take the time to review the comprehensive Penn State University Libraries online tutorial concerning patents.
We also recommend the USPTO 7-step strategy for searching patents.
There are many patent resources available on the web, which you may wish to review, but we recommned the folloiwngthe following tutorials:
Online Tutorials:
Leon Castro, NUTech
Thinkers and Tinkerers: How to Conduct a Patent Search
IPWatchdog
Patent Searching 101: a Patent Search Tutorial
Before you start: Get organized!
As you conduct your search you will be examining a great deal of information including patent descriptions, claims, drawings etc. You need to be sure to DOCUMENT, DOCUMENT, DOCUMENT where you search, what you find, what is useful, and what is not useful. This will provide you a "trail" of information and will benefit you especially if you elect to contact a patent attorney for assistance.
You may wish to use a paper notebook or electronic spreadsheet file. Many of the search results are downloadable to a Word or pdf document.
Keyword search
You may wish to slightly alter the USPTO process and begin by keyword searching your defined terms in one of the free online patent search sources. This is a quick way to identify potential additional terms and to identify relevant codes for classification searching. Keyword searching is also available, at no charge, in the USPTO classification sources discussed below.
There are several free sources but Google Patents and Free Patents Online are listed here due to their ease of use.
Both sites allow you to search by keyword. You may then locate Cooperative Patent Classification (CPC) letter/numbers for classification searching.
Classification search
The U.S. Patent Classification (USPC) was the USPTO system for over 100 years. Recently, however, a new classification system, Cooperative Patent Classification (CPC), co-developed with the European Patent Office (EPO). replaced the USPC for utility patents. (USPC will remain in use for U.S. design and plant patents.) For more complete information please click here to go to the CPC web page and click here to access the USPTO Classifications and Standards page.
You may search the classification numbers you located in Google patents via the USPTO website. Patents issued from 1790 to 1975 are searchable only by issue Date, patent number, and current US classification. Patents from 1976 to the present are keyword searchable.
USPTO Patent and Full Text and Image database
The list of USPTO classification sections are available here:
Patent Applications
Applications are available from 2001 to the present. To search, click here:
The next step: Searching Prior Art
Prior Art search
To complete a thorough patent search you will need to identify the "state-of-the-art" in regard to your invention. Click here to go the prior art page.