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Engineering Library

Class Searching: Identifying Patent Classification Numbers



[image]Index to the U.S. Patent Classification

The Index to the U.S. Patent Classification System is an annual publication from the USPTO. Each edition presents an alphabetical arrangement of subjects included in the manual as of that date. Since the manual periodically adds, removes, and revises subject headings, you should try to use the most current index.
Use the Index to identify relevant class and subclass numbers alphabetically by subject. You may need to look for several alternative terms or synonyms to find your subject in the index; look for all terms you can think of that describe the invention. Look up what your invention is as well as what it does.


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For example, to find patents related to aluminum baseball bats, look up the index heading Baseball and find the subheading Bats.

Write down the class and subclass numbers that best describe your invention. (Because few inventions fit perfectly in one classification, we usually recommend that searchers identify several relevant headings and subheadings.)
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Manual of Classification

The index to the classification manual presents classifications in alphabetical order without showing related classifications. The Manual of Classification (the looseleaf binders) lists classifications from more general to more specific. To determine whether more specific classifications are available for your classifications, take the most relevant number you found and look it up in the manual.

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For example, in the search for baseball bats, you would look up class 273 and find subclass 72R. Immediately below 72R is subclass 72A, which specifically covers baseball bats with metal shells.

Notice that some entries in the manual begin with one or more periods. The number of periods provides a subject hierarchy, like the outline for a term paper; an entry with two periods is a more specific subset of the entry with one period above it, but less specific than the entry with three periods below it, for example. Subclass names written in all capital letters are the most general.

Write down your revised class and subclass numbers at this point. Keep in mind that your subclass numbers are likely to be different from the ones you found in the Index. Use only the most specific subclass to your invention.

It is also a good idea to browse the entire hierarchy, starting at the top of the class and looking at all the capitalized subclasses. You may find additional subclasses that pertain to your search.

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Class Definitions

The most specific information about a classification number appears in the Patent Classification Definitions in the patent area microfiche cabinet.

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When reading the definitions, you should start by reading the definition for the class as a whole...
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...and then read the definitions for your specific subclass.

Once you have identified the classification and subclassification numbers you wish to search, you are ready to search CASSIS to determine which patents match your classification.

Guide to searching CASSIS

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Last modified: Thursday September 23, 2004