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Patents and Patent Searching: How to Search

What is a Patent Search?

A patent search is a process of identifying existing patents related to an invention or idea. A patent search is not legally required, but it can be a crucial part of figuring out whether any prior patent will interfere with your ability to acquire a patent or there is duplication of research efforts. Filing for a patent and acquiring a patent can be expensive. Before applying for a patent, even before you start a R & D process, you should conduct a patent search.

Challenge of Patent Literature

  • Patents don't describe inventions as they appear in the market. 

Patents may cover broader concepts and they don't specify the final packaging, detailing, manufacturing processes, trademarked names, and other aspects of products.

  • Patents don't include product names. 

Searching patents by names of products, whether Formica or Blackberry mobile devices, rarely provides a direct path to the invention in question. Final product names are often determined long after patents are filed (trademarks rather than patents protect product names). In addition, the final product may be an amalgamation of several patents. So searching patents for, say, Apple's popular iPad requires knowing that the relevant patent was titled “Proximity detector in hand-held device" and never once uses the term iPad.

  • Patents aren't easy to read.

Patents are legal documents and usually written by attorneys for analysis by patent examiners. They lack the directness of specifications, technical standards, or other types of descriptive documents. They often employ a specific legalistic vocabulary.

  • Patents aren't a true form of scientific literature.

While patent applications are subject to examination by patent examiners, they are not subject to peer review and are not required to demonstrate proof of success through experiments and processes usually associated with scientific research.

Patent Classification Systems

Patent classification is used to classify or organize patents based on their features.  A patent document usually has at least one or more patent classifications assigned to the document. Use the classifications to expand your search. Below are some patent classifications.

  • Cooperative Patent Classification (CPC)

In force from January 2013. Replaces the European Classification (ECLA). Jointly managed by United States Patent and Trademark Office (USPTO) and European Patent Office (EPO).

  • International Classification for Industrial Designs (Locarno Classification)

Locarno classification "is an international classification used for the purposes of the registration of industrial designs." Available on WIPO site.

  • International Patent Classification (IPC)

IPC "provides for a hierarchical system of language independent symbols for the classification of patents and utility models according to the different areas of technology to which they pertain." Provided by WIPO.

  • United States Patent Classification (USPC)

From United States Patent and Trademark Office (USPTO).
Note : From 2015, USPTO no longer actively assign USPC to utility patents. Plant and design patents will continue to be published with USPC symbols.

Search Strategy

Here is a Search Strategy prepared by USPTO which may give you a clue to patent searching.


  1. Brainstorm keywords related to the purpose, use and composition of the invention.
  2. Look up the words in the Index to the U.S. Patent Classification to find potential class/subclasses.
  3. Verify the relevancy of the class/subclasses by using the Classification Schedule in the Manual of Classification .
  4. Read the Classification Definitions to verify the scope of the subclasses and note "see also" references.

Access Full-Text

  1. Search the Issued Patents and the Published Applications databases by "Current US Classification" and access full-text patents and published applications.

Review and References

  1. Review the claims, specifications and drawings of documents retrieved for relevancy.
  2. Check all references and note the "U.S. Cl." and "Field of Search" areas for additional class/subclasses to search.


Search Examples