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Biomedical Engineering: How Do You Search Patents

Keyword Searching for Patents

First, consider your technique...

Remember that computer searches are based on matching words and that the words and phrases used in patent documents may not be the first ones that come to the mind of an average person. What describes your invention? What is unique? What is new?


Imagine that you have just invented the Koosh ball. You cannot search by the name "Koosh ball" because,

  • That's a product name and those aren't part of the patent.
  • You will find patents with the expression "koosh ball" but these will be in patents for inventions that use or incorporate koosh balls.

You need to describe the ball in words that would match those in the patent, searching for something like:

(spher$ OR ball) AND (rubber OR elast$) AND filament$

The patent description for a Koosh ball includes many of these words:

An amusement device comprising a core region, and plural, elongate, floppy, tiny-diameter, elastomeric filaments, each having a cross-sectional dimension which is extremely small in relation to its length, said filaments radiating in plural angularly offset planes in a dense, bushy configuration from said core region to form a generally spherical object, with the filaments being sufficiently floppy to collapse significantly on impact, thus to absorb enough energy to . . . US patent 4,756,529, 1988

Fortunately, most inventions are not such a challenge to describe, however, this is an excellent example of the language used in patents!

Search Tips

Like article searches:

  • Off-topic results are a fact of life; to be thorough the searcher should look through everything. Titles are often weak indicators of content.
  • If you miss something you get no warning. Your ability to generate synonyms and alternate descriptions can make or break the search.

Unlike an article search:

  • In a novelty search, you are trying or hoping to prove that there are no inventions close to yours. You have to be sure that you are not getting anything because nothing is there rather than because you are not asking the right questions.

Other Tactics for Finding Patents

Classification (class) numbers 

Patents are assigned subject-based class numbers much like the class numbers for books in a library; you can search by class number as well as words. (In fact, in pre-computer database days, this was the only way to search for patents). Experience has shown that class number searches can retrieve additional useful patents when done in parallel with a keyword search.

Strictly speaking, you would work through the patent classification tables, determine the most appropriate class numbers then carry out a search based on those numbers. A fast alternate is to run a keyword search, note the class numbers used on the most interesting patents and carry out a search based on those numbers. Both national (US or Canadian) class numbers and the International class numbers are worth following up.

This 7-Step U.S. Patent Search Strategy Guide from the United States Patent and Trademark Office has a good walk-through of how to search with class numbers (in a U.S. context, of course).


Patents have bibliographies, like those in journal articles and books, referring to similar inventions. It is possible and recommended that you follow up these citations, both older, to see what ideas the inventor reviewed in writing the patent, and newer, to find who cited the patent you are looking at. Many search systems now make these hyperlinks for ease of searching.


A patent must have a person (not a corporation) named as an inventor. This sort of search will work best if you know who invented the device you are looking for.

Patent Assignees

An inventor working for a company will often assign ownership of the patent to the company he or she is working for. Searching for a company may find some of the technology developed by their employees. Keep in mind that companies can licence the right to use patents from other companies (there is no database listing who has licenced what) and you rarely hear about that.

Finding Older Patents

Canadian and US patent databases are searchable by keywords from the documents (abstracts, claims, descriptions etc.) back to the mid 1970's. Before that:

Country Searchable by:
Canadian Keywords from the citation information - author, title, or class number.
1869 to present 
US - PTO Class number only
1790 to present 
US - Google Keywords and all information - standard caveats apply for any Google search
1790 to present