This guide has been written to help students at Heriot-Watt University find patents that are relevant to their coursework. It does not cover checking if your idea or invention is already patented, and does not give legal advice.
References for patents are normally two letters followed by a string of numbers, e.g., GB2523978; US7345671; US3633.
Look for (A), (A1) or similar in the patent number to identify patent applications. A patent application does not mean the patent has been awarded. In the UK a new patent number is issued when an application becomes a patent, in the US the same number is used.
Almost all patents are publicly available. In the UK, access to patents covering "military technology or prejudicial to national security or public safety" may be restricted. Patent offices in other countries will have similar restrictions.
Use Espacenet to find a patent from the patent number. Espacenet is run by the European Patent Office, but also includes patents from many countries outside the EU. It is a reliable resource for finding patents, and includes most post-1890 UK patents.
Some other resources for finding patents are listed at the end of this page.
There are two ways to find patents about a topic:
Searching by keyword
You can search Espacenet for keywords that appear in the title or abstract of a patent. However, this can be hit-or-miss as the terminology used in patents may not be what you expect. It might be easier to find patents via the classification scheme ...
Browsing via the classification scheme
All patents are classified, i.e. assigned to categories that describe what they are about. Most patents are assigned to more than one category, so have more than one classification number.
There are two systems for classifying patents, the older "International Patent Classification" (IPC) system, and the current "Cooperative Patent Classification" (CPC) system, which was introduced in 2013. The CPC system is more precise, and many older patents have been given CPC numbers in additional to their original IPC numbers.
The broad categories for CPC are:
A: Human Necessities
B: Operations and Transport
C: Chemistry and Metallurgy
E: Fixed Constructions
F: Mechanical Engineering
Y: Emerging Cross-Sectional Technologies
Combining these methods
The easiest way to find patents about your topic might be to combine these two methods: use a keyword search to identify some relevant patents, and then browse through the categories where these patents have been classified.