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Intellectual Property & Patents

Engineering Librarian & CAPLA Liaison

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Paula C Johnson
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Whys & hows of patent searching

You have an idea for an invention — or have gone so far as to create a prototype. Before marketing your invention, you will need to determine if your invention has already been patented. To do this, conduct a thorough patent search. This will usually involve searching a number of different patent sites, so it's useful to keep a log of all your search activity to avoid duplicate efforts.

See General Information Concerning Patents and Patent Process Overview for more information.

You can begin your search the following way:

1.  Brainstorm keywords to describe your invention, such as synonyms.

2.  Use your keywords to search for a similar match of your invention in Google Patents. The advanced search lets you enter phrases, exclude words, etc.

3.  If you find a similar invention, write down its class and subclass.

4.  Use the class and subclass to search patents and patent applications with the USPTO website classification search. The USPTO website is more current than Google Patents.

[Note: The default search is CPC (Cooperative Patent Classification), which harmonizes the former European Classification (ECLA) and United States Patent Classification (USPC) systems.]

5.  Trace related patents through references.

If you need to look through a large number of patents it might be worthwhile to make an appointment to use the PubWEST database at a Patent & Trademark Resource Center (PTRC). This database is not accessible except through a PTRC workstation.

Why use classifications over keywords?

The primary purpose of a patent classification system is to provide effective and efficient means of organizing and retrieving patent documents by technological subject. Espacenet is particularly useful in drilling down on a classification number.

Searching by classification is more helpful than keyword searching because it is:

  • language independent.
  • terminology/jargon independent.
  • applied by experts (i.e. patent office staff).
  • available for (old) patent documents that lack searchable full text.
  • useful for concept searching.

While it is possible to search patents using just keywords, the most effective way to conduct a comprehensive patent search is by classification. Classification helps bring together similar devices and concepts, even when different terms have been used to describe them. The following are more reasons why searching by classification is useful.

  • Classifications have definitions and hierarchical relationships to one another, unlike keywords.
  • When a device is truly new, terminology is not set. For example, before personal computers were invented, a mouse was just a type of rodent. The inventor of the first "Computer Input and Display Control" would not have found related devices by searching the keyword "mouse."
  • Classifications are used both as tools for finding patents and for assisting in the assignment of patent applications to examiners for examination purposes.

See a Detailed Seven Step Search Strategy from the USPTO.

In addition to the more frequently used (in the U.S.) CPC system for classification, there is also the International Patent Classification (IPC).

Free patent search tools