Patent classification (CPC / IPC)
Also called CPC, IPC, Cooperative Patent Classification, International Patent Classification, classification symbol, classification code, patent class
Patent classification is a system for organizing patent documents into technology groupings based on common subject matter1, each grouping identified by a symbol2,4. The two systems in wide use are the International Patent Classification (IPC) and the Cooperative Patent Classification (CPC).
The IPC was established by the Strasbourg Agreement (1971) and provides a hierarchical system of language independent symbols2. The CPC is an extension of the IPC and is jointly managed by the EPO and the US Patent and Trademark Office3. The IPC's primary purpose is to provide an effective search tool for retrieving patent documents, in order to establish novelty and evaluate inventive step4.
How the hierarchy works
The IPC separates the whole body of technical knowledge into the hierarchical levels section, class, subclass, group and subgroup, in descending order of hierarchy4. The CPC is divided in the same way: sections, which are subdivided into classes, sub-classes, groups and sub-groups3. The table shows the IPC symbol rules, with examples taken from WIPO's Guide to the IPC4.
| Level | Symbol rule | Example |
|---|---|---|
| Section | One capital letter, A through H. There are eight sections, the highest level of the hierarchy4 | H (Electricity)4 |
| Class | The section symbol followed by a two-digit number4 | H01 (Electric elements)4 |
| Subclass | The class symbol followed by a capital letter4 | H01S (devices using the process of light amplification by stimulated emission of radiation [laser])4 |
| Main group | The subclass symbol, a one- to three-digit number, an oblique stroke and 004 | H01S 3/00 (Lasers)4 |
| Subgroup | The subclass symbol, the main group number, an oblique stroke and a number of at least two digits other than 004 | H01S 3/14 (Lasers characterised by the material used as the active medium)4 |
- A complete IPC symbol combines the section, class, subclass and main group or subgroup4.
- The hierarchy among subgroups is determined solely by the number of dots before their titles, not by the numbering of the subgroups4.
- The scope of any classification place must be interpreted within the scope of all its hierarchically superior places4.
- Depending on the content of a patent document, more than one classification symbol may be applied4.
IPC vs CPC
| IPC | CPC | |
|---|---|---|
| Origin | Established by the Strasbourg Agreement (1971)2 | Initiated as a joint partnership between the USPTO and the EPO, developed in large part from the European Classification system (ECLA) modified to comply with IPC standards5 |
| Managed by | Administered by WIPO5; the Strasbourg Agreement established the Special (IPC) Union4 | Jointly by the EPO and the USPTO3 |
| Sections | Eight, A through H4 | Nine, A to H and Y. Section Y is for general tagging of new technological developments and cross-sectional technologies3 |
| Size and change | A new version enters into force each year on January 12 | Approximately 250 000 classification entries, constantly expanded as new technical fields emerge3 |
The USPTO moved from the United States Patent Classification (USPC) to the CPC on January 1, 20131. The USPC is now kept mainly for historical purposes, and only its plant and design classification material is still updated1.
Using classification in a search
WIPO's guide to the IPC says the IPC may be used for novelty searches, patentability or validity searches, infringement searches and informative (state of the art) searches4. See patentability search, invalidity search, freedom to operate and state of the art search. The guide describes this way of finding the right place in the IPC4:
- State the technical subjectEstablish clearly the technical subject of the search and identify the technical terms that cover the field4.
- Find the subclassUse the Catchword Index or term searching of the electronic IPC. If that does not lead to a pertinent field, scan the eight sections, then the classes and subclasses by title4. An alternative is to text-search patent documents by technical terms and analyze the classification symbols assigned to the documents retrieved4.
- Check the references, notes and definitionCheck the references and notes in the subclass title, and study the definition if one is available, since definitions give the most precise indication of a subclass's scope4.
- Choose the main group and subgroupScan the main groups of the subclass, then the one-dot subgroups. If the chosen group has subordinate groups with more dots, the group to search is the most appropriate and most indented one4.
- Widen, combine and re-checkAfter searching the chosen group, consider hierarchically higher groups, which may hold a wider subject including yours4. Where multiple classification or indexing is applied, begin with a combination of symbols to make the query specific, and broaden it afterwards using the most pertinent symbols alone4. Failure to retrieve pertinent documents may mean the proper place in the IPC has not been located4.
Questions people ask
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Run Novelty SearchWhat is the difference between the IPC and the CPC?
The IPC was established by the Strasbourg Agreement (1971) and is administered by WIPO2,5. The CPC is an extension of the IPC, jointly managed by the EPO and the USPTO, with nine sections (A to H and Y) instead of the IPC's eight3,4.
What does a symbol such as H01S 3/00 mean?
It combines a section (H), a class (H01), a subclass (H01S) and a main group (3/00). In WIPO's Guide to the IPC, H01S 3/00 is titled Lasers4.
Can one patent document have more than one classification code?
Yes. Depending on the content of a document, more than one classification symbol may be applied, for example where it relates to both a product and a process for making it and there are groups for both4.
How it connects
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