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Using Patent Databases and Finding Patents

An introduction to patent searching, with links to freely available patent databases and suggested search strategies.

Classification Searching - "Classic" Espacenet

What the examiners recommend for subject searching

For careful, comprehensive subject searching, patent examiners emphasize searching by patent classification. That is:

  • Figure out the matching subject classification(s) for your area of interest
  • Get the list of patents assigned (by various patent offices) to that subject classification
  • Examine the patents in the list; the examination will be both for information about that patent and for cited literature.


NOTE:  The examples below are based on "Classic Espacenet."  There is a new Espacenet after a re-design.


The Cooperative Patent Classification (CPC) System  is the patent classification system used in Europe, the U.S., and in various other parts of the world.  In classification searching, it is your job to match your area of interest to the right subject classification(s).  Two approaches are to: 

  • Use subject classifications on known patents found from other work; for example, finding patents from company or keyword searches.
  • Go directly to the classification tables to figure out the best codes

CDC snip 2018


At the CPC tables you may:

  • Browse the tables (this is a challenging task for most of us)
  • Search by keyword or, if you have it, by classification to find a location within the classification scheme.CPC search box snip 


1. For example, we can search "computer mouse" to find where that fits in the CPC:

  • "Computer mouse" finds a quick match but the usual advice is to try various term related to your interest
  • The language of patents is not always obvious.  Trade names are typically not found.


2. Looks as though we will want to consider the broad category of G06F3/00:

  • Click on the classification to expand the CPC scheme for that section
  • Ask yourself if this seems like the correct area for computer mice
  • Notice notes pointing to other classes or places and giving clarification
  • Notice the dot (•) structure showing a hierarchical arrangement of the headings.



3. To see the patents assigned to the classification we:

  • Select the classification of interest with a click in its box (this selected classification is for example only):


4. The selected classification will fill in the "Selected classifications" box (to the left on the page).

  • /low selects the classification AND the classifications under it in the hierarchy --- sometimes there are no classification under the one selected
  • /exact selects only that classification
  • "Find patents" searches the classification in the Espacenet database
  • "Copy to search form" pastes the classification to the Espacenet Advanced Search form in case we want to limit the search with additional requirements.


5. "Finding the patents" for this classification gives a set of at least 488 documents.  It's a lot to consider.

  • As a first step, we will want to get a sense of the direction of the search.  Does this area of invention match expectations?
  • Engineers and inventors usually want to see the drawings.  For more of those go to:  
    • Mosaics or
    • Original document 
  • It may be necessary to go back to the CPC Tables to reconsider the right classification
  • If we see a patent of interest, we will want to note the assigned classification codes and investigate them.


6. Finally, we will consider the goal of our project and plan our work:

  • For those exploring patent searching, we recommend continuing until working with classifications and patent documents seems comfortable.
  • For inventors preparing to file for a patent, the U.S. patent examiners recommend examination of each document found in the classifications likely to be assigned to the invention.  There is a lot of work to be done.


From the USPTO

Also, the U.S. Patent and Trademark Office (USPTO) pages offer the Seven Step Strategy for classification searching.  The approach illustrates use in the U.S. patent databases but, once understood, the technique can be used in other patent databases.

Classification Resources from the USPTO offer help in understanding currently used classification schemes and the (mostly) previously used U.S. Patent Classification.

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