Research Guides: Patents: Search tips

Classification

Classification vs. Keywords

Patents are classified into different categories, making it easier to find similar inventions without having to think of keywords to describe them. Searching by classification is more efficient because it is:

Language independent
Terminology/jargon independent
Applied by experts in the patent office
Available for patents that do not have searchable full text
Useful for concept searching.

The Cooperative Classification System is one commonly used system.

For example, a patent for Gaze Detecting Heads-Up Display Systems (US2013222235) is classified with 3 CPC codes, one of which is:

G02B27/0172

The class G02B27 covers optical apparatus; the next level down, 0172, refers to head-up, head-mounted systems characterized by optical features.

It's a good idea to start searching for patents with keywords, then make note of the classifications applied to patents you're interested in and search using those. In espacenet, there's a classification search screen with helpful tips in the sidebar.

For help searching for patents using classification systems, contact a librarian.

Cooperative Classification
The CPC is a patent classification system developed by the EPO and USPTO. Searchable in the EPO's Espacenet system.
WIPO International Patent Classification (IPC)
This is a hierarchical system used by more than 100 patent offices to classify documents. Searchable in most patent databases.
U.S. Patent Classification (USPC)
This is a system consists of about 450 classes and 140,000 subclasses, including a class for plant patents (PLT) and 33 design classes. It is being phased out in favour of the CPC

Anatomy of a US Patent Document

Classification codes are just one piece of information in a patent. This excellent guide from Queen's University librarian Michael White outlines other key parts of US patents.

Anatomy of a US Patent Document