Most patent information is openly available online. Patent databases and search engines vary by breadth of contents, national or international coverage, basic interfaces and advanced search tools.
Google Patents and the USPTO's Public Patent Search have different advantages. Use both to ensure a comprehensive search strategy.
|Google Patents||USPTO Public Patent Search|
|All patent documents, except recent months||All patent documents, updated weekly|
|USPTO and 100+ other jurisdictions||USPTO patents only|
|Easy-to-use Google-style interface||Complex interface for precise searching|
|Document searching for all patents||Document searching 1976-present, index searching 1790-1975|
|Searches images with Optical Character Recognition||Searches text (more reliable)|
1. Search by classification.
The most effective way to search for patents for a specific area of technology is to identify the most relevant classes and subclasses in the Cooperative Patent Classification (CPC) scheme.
a. Search for keywords in patent texts and identify the most common classes/subclasses. Do this by (1) searching Google Patents and reviewing the statistics under "Top 1000 results by filing date" > CPCs; or (2) using Espacenet's CPC-browser.
b. Search for keywords in class/subclass titles and definitions. Do this with the USPTO's Classification Text Search.
c. Search by keyword in a patents database, find relevant patents, then review their classes and subclasses. In Google Patents, look for "Classifications". See "Useful links" for a link to the USPTO's comprehensive list of field codes.
d. Browse the CPC scheme.
2. Search by field.
Patent fields include inventor, assignee (owner), and patent number. Field searching is most useful for finding a known patent.
3. Search by keyword.
An increasing proportion of patents are available online with full text, making keyword more effective. But keyword searches may retrieve an overwhelming number of results or may fail to reflect the technical language used in patent writing. Use keyword searching as a step to identify classes and subclasses; and to supplement classification searching.