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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 using 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.

Here is a video on classification searching in Espacenet from the Open Source Patent Analytics Project.


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.

CPC table


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


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.

cpc mouse


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.

cpc expanded

(and more)


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):cpc box selection


4. Notice that clicking in the box fills in a a search form to the right.

cpc box to search


  • /low selects the classification AND the classifications under it in the hierarchy --- sometimes there are no classification under the one selected
  • to select only one classification when the system forces more, requires using the "Advanced Search" option --- selecting a "classification search" with an "=" operator.


5. Click on cpc find patents to see the list of patent documents assigned to the classification and listed in the Espacenet database.

cpc results list


6. "Finding the patents" for this classification gives a set of more than 440 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?
    • Click on the title of the patent for more information.
  • Engineers and inventors usually want to see the drawings.  For more of those, notice:  

‚Äčcpc display with drawings

  • 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.


7. 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.  It is a challenging task.

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.

More on using Espacenet

For more on using Espacenet:

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