Why Patent Search? To verify the scope of the prior art in order to write a better patent application for a product that advances the field; to verify a potential invention is new; to verify a potential invention is patentable; to see what your competitors are doing; to harvest knowledge; because the patent examiner is going to search, etc. There are many sound reasons.

When a nonprovisional patent application is filed, a USPTO patent examiner searches to find if the invention as defined in the claims is patentable- does the subject matter of a patent application advance the state of the art in the field of endeavor of the invention? The examiner does this search because an invention cannot claim prior art as their own in a patent application, only what is new. ( “Prior art” refers to all that is already public knowledge (patent and nonpatent) in the areas of science and technology)

Knowing what is new versus what is already public knowledge allows the patent application writer to correctly identify the invention. Once a nonprovisional patent application is submitted, no new matter is allowed to be added to the application. (Note: A Provisional Patent Application is not examined when it is submitted to the USPTO. Additional steps must be taken for a provisional patent application to become an issued patent. See for more information.)

The search requirement steps that the patent examiner must follow are found in MPEP 904.02 General Search Guidelines [R-3] - 900 Prior Art, Classification, and Search:

904.02 General Search Guidelines [R-3]

In the examination of an application for patent, an examiner must conduct a thorough search of the prior art. Planning a thorough search of the prior art requires three distinct steps by the examiner: (A) identifying the field of search; (B) selecting the proper tool(s) to perform the search; and (C) determining the appropriate search strategy for each search tool selected. Each step is critical for a complete and thorough search.

When determining the field of search, three reference sources must be considered - domestic patents (including patent application publications), foreign patent documents, and nonpatent literature (NPL).

This Seven (7) Step Strategy (on the left below) from the UPSTO provides a search strategy for considering the first of the reference sources--domestic patents including patent application publications. Not Just Patents has provided additional information for a Quick Start patent search on the right side of the chart below.

A Quick Start patent search is a way to see how a particular field looks (U.S. Domestic) for what has already been invented or disclosed to help an inventor, potential inventor, investor, etc decide if it is best to invest more in pursuing a potential patent through all the patenting steps (See StepsToAPatent for more information.)

After you’ve taken a quick look, Not Just Patents ® Legal Services can help with a more thorough search to see if your invention has enough ‘inventive step’ and other criteria to be meet patentability requirements including those identifiable using the other references sources that an examiner will search (foreign patent documents and nonpatent literature). Not Just Patents can also write your application, complete the drawings and get your patent application through the rest of the patent steps (and verify if your product is a good candidate for a federal trademark registration). Since both nonpatented and patented products or inventions can prevent a new patent application from issuing, a search should not be limited to issued patents and patent applications if an inventor wants a patent application that takes prior art, obviousness and enabling disclosure issues into account. (While a pre-application patent search is not mandatory in a nonprovisional patent application, an enabling disclosure is required.)

Plan for a Strong Patent, not a filled in form. An Issued Patent is very difficult to get--in 2009 56% of disposals were Abandoned Applications--more than half did not issue. For more statistical information on patents see the USPTO web site or the Not Just Patents site: See the USPTO web site at  Scam Prevention for information on the different types of scams that are directed at inventors and their inventions and how to prevent being scammed by an invention promotion company.

 Seven Step Strategy

 Quick Start


Note:  “Prior art” refers to all that is already public knowledge (patent and nonpatent) in the areas of science and technology.


More to think about

1. Brainstorm keywords related to the purpose, use and composition of the invention.

Key words should include both technical terms and end-user oriented terms and lots of variations. Often technical terms are used in patents and patent applications but user oriented terms are used for products that have already been released and are being marketed. An example is: “Low Volume Flowable Solids Distributor”  or “Granular Dispensing Apparatus” that may be marketed/sold as a type of salt or other seasoning dispenser. An internet search for “salt dispenser” may come up with a similar or same product but a patent search using “salt dispenser” may not identify the most relevant patent. (But “salt shaker” might find it! It depends on accidents of language.) Remember that search engines look for words, not concepts. A quick mechanical search using only a few words may completely miss relevant “prior art.”  Inconsistent terminology in the many technology fields can make searching very difficult.

Try to define the Invention Information.’ Invention information refers to how the subject matter of a patent application advances the state of the art in the field of endeavor of the invention. Or what does this invention do that is new or an improvement over everything that is already public knowledge.

Purpose and Use determine the class that an invention falls into (broad group). A concept called ‘Proximate Function’ is useful here. The proximate function, when used as a basis for classification, is generally applied to a process, structure, or composition for performing general operations in which a single causative characteristic can be identified and which requires essentially a single unitary act; e.g., agitating, cutting, heating, filtering, etc. The list of U.S. Classifications is a list of proximate functions.

The composition (elements or individual components) of the invention can be very critical, these determine which subclass an invention falls into. A subclass is aimed more at how the invention is described and claimed, much more specific and often patent searches are conducted before claims are written, making the search potentially unreliable.

Note: When the USPTO patent examiner searches for relevant prior art, the search covers the invention as described and claimed (its proximate function) not just key word searches.

2. Look up the words in the  Index to the U.S. Patent Classification to find potential class/subclasses.

Some of the classifications (this example had 10) for the “low volume flowable solids distributor” (salt shaker) example would be 222/196 DISPENSING: JARRING AND/OR VIBRATING or  222/564 DISPENSING: WITH INTERIOR MATERIAL GUIDE OR RESTRICTOR or   239/500 FLUID SPRINKLING, SPRAYING, AND DIFFUSING: SERIALLY ARRANGED DEFLECTING SURFACES. See list of U.S. Classifications.

Note: Even though Statutory Invention Registrations (SIR) are not patents they can be searched at the USPTO Patent Database, and even though they are not patents, they are considered prior art by patent examiners. Some other databases classify SIRs as nonpatent literature (NPL) and they must be searched independently of patents or patent applications.

Note: In some fields (software developments as an example), much pertinent prior art may not be found in issued patents and patent applications but in publications and limited circulation documents such as technical manuals (nonpatent literature (NPL)).

3. Verify the relevancy of the class/subclasses by using the  Classification Schedule in the Manual of Classification .

Knowing the ‘Proximate Function’ of the device is important for knowing which class/subclasses should be searched.

4. Read the  Classification Definitions to verify the scope of the subclasses and note "see also" references.

If a device has more than one ‘Proximate Function’ it may advance the field (see Invention Information) in one class but not in another. Many product improvements come from understanding technology in one field and applying it to another field in a non-obvious way.

Access Full-Text

5. Search the Issued Patents and the Published Applications databases by "Current US Classification" and access full-text patents and published applications.

The USPTO has search templates available for searching specific classifications. These search templates also give sources for searching relevant nonpatent literature (NPL).

The public can also access abandoned applications, see MPEP 711.04 Public Access to Abandoned Applications for more information.

Review and References

6. Review the claims, specifications and drawings of documents retrieved for relevancy.

It is not difficult to use search terms to find hundreds or thousands of patents and patent applications that contain specific search terms but it is much more difficult to determine which claims, specifications and drawings are relevant as prior art. A ‘review’ as part of a patent search process becomes an opinion of the searcher as to relevancy. However, the words used in a patent document are an accident of language--they depend more on who wrote the patent document and their use of language--rather than necessarily the relevance of those words to the concept that someone is trying to search. If the searcher does not understand the claims, specifications and drawings, it is difficult to make this review and search results might actually turn out to be collection of documents that show a popularity of certain words in a published patent document rather than a measure of relevancy. Redundancy is inherent in a patent document that meets supporting requirements, i.e., the claims are supposed to be supported by the specification, the written description of the drawings is also supposed to support the claims, etc.

7. Check all references and note the "U.S. Cl." and "Field of Search" areas for additional class/subclasses to search.

See Field of Search in the attached Manual for more information.



An Internet search should be considered to locate relevant prior art (nonpatent literature) that is already in the marketplace. Many products are never patented but are still considered prior art. Internet sources can also help with learning about the field and technology, to identify major manufacturers in the field, to identify  potential assignees, to identify additional search terms and to identify relevant product information.



PATENTSCOPE® Search Service from the World Intellectual Property Organization enables you to do full-text search in over 1.6 million published international patent applications from the first publication in 1978. (Patentscope® is a registered trademark of WIPO-international registration number: 879539)

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