Patents: Patent Databases

• There is no single database that provides free access to all patent documents in electronic full-text format.
• Keyword searching is limited when full-text documents are unavailable.
• Fee-based (subscription) databases tend to include more full-text patent documents, or have indexed titles and abstracts of non-digitized patent documents.
• Full-text documents for U.S. patents are available in the USPTO database going back to 1976 (with a few but not all going back to 1971).
• Although Google Patent Search claims to provide full-text for all U.S. and most European patent documents, information tends to be inaccurate and unreliable because optical character recognition (OCR) was used on scanned (TIFF) images of original patent documents, some of which were written in cursive script.
• Misspellings and OCR errors are not corrected by patent offices, making comprehensive searching more difficult.  Certificates of Correction are appended as image files and therefore are not searchable by keyword.
• Terminology and descriptions used are often vague, ambiguous, obsolete, and inconsistent, making keyword searching unreliable.  Names for inventions are often developed only after patent approval and as devices enter commerce.  Examples: "amusement device" for "toy" or "water closet" for "toilet" or "four rectangular uprights supporting a planar surface" to describe a "table"
• Some databases include English translations of patent titles and abstracts, particularly for Japanese, Chinese, and Korean patent documents.
• Patent documents include published applications, many of which will never become granted patents, but describe "prior art."  Under the PCT, all patent applications filed since 2001 must be made publicly available (within 18 months after the filing date).

Searching by patent classification code circumvents many of the limitations of keyword searching for locating records and documents about inventions.

Two patent classification systems are currently in use:

• Cooperative Patent Classification (CPC)
• International Patent Classification (IPC)

Note that the CPC replaced the former United States Patent Classification System (USPC) in January 2015 and the European Classification System (ECLA) in 2013.  The CPC can be searched with keywords using the Classification Search function in the Espacenet database.