Six Easy Steps to Highly Effective Patent Searching

Six Easy Steps to Highly Effective Patent Searching
You can speed up your design cycle time by mining patents for information. Here, a skilled patent attorney shares his secrets to faster and better searches.
Craig Fieschko — Design News, June 6, 2005

A patent is often described as a monopoly (generally limited to 17-20 years) granted to the inventor of a new and useful machine, process, or other invention in exchange for the inventor’s complete written description of how to make and use the invention in a patent application. These details can be highly useful to design engineers, who can use patents to learn how others have approached similar problems, what design strategies have and have not worked in the past, and to get a handle on what is state-of-the-art in their field.

But with almost 7 million U.S. patents covering virtually every field of technology, it can be a lot like trying to find a needle in a haystack to locate the patents that are most relevant to your design problem. In this article, I share some of the basic search strategies I use as a patent lawyer (and former engineer) to sift through the clutter.

This article assumes that you’re using the search engines of the U.S. Patent and Trademark Office (USPTO).

First a Few Basics on Patent Searching

Some of my favorite patent-searching resources on the Web are listed in the sidebar, and the following discussion will assume that you’re using the search engine of the United States Patent and Trademark Office (USPTO), the government agency that administers the U.S. patent system.

While you can simply enter a string of terms into the search engine and obtain all the patents or published applications that contain these terms, the USPTO’s search engines, like most patent search engines, helpfully allow “fielded” searching. Terms can be entered in certain fields, such as Title, Abstract, Assignee (Owner), etc., to locate patents or published patent applications having the entered terms in the specified fields (in the specified sections of the patents or applications).

The USPTO also allows strings of fielded search terms to be connected with Boolean terms such as AND, OR, and ANDNOT, and parentheses can be used to order the connected terms (see a sample search on page 80). Additionally, the ends of search terms can be truncated and the “wildcard” symbol $ can be substituted to search for variants of the term. For example, “circuit$” will search for the terms circuit, circuits, circuitry, etc. (Note that a term may not be truncated to less than four characters.) Search terms can also be combined in strings by using quotation marks. For example, entering the term “circuit board” (in quotes) will search for the adjacent words “circuit” and “board,” in that order.

It might seem that a good way of locating relevant patents is to search in the Abstract (ABST) and/or Title (TTL) fields. Unfortunately, this is rarely the case. Titles are usually vaguely worded because patent attorneys fear the potential ramifications of a specifically worded title. The same is true of most Abstracts, which poorly represent the contents of their documents.

So it’s no surprise, then, that an Abstract and/or Title search should never be regarded as complete and accurate. A Specification (SPEC) search, which extends to the detailed bodies of the patents or applications, is far more complete. Nevertheless, if a search strategy results in a very large number of hits, it may be preferable to begin a search by limiting it to the Title (TTL) or Abstract (ABST) fields.

Other useful search fields include the Assignee (AN) field, which may list the owner of the patent, and/or the Inventor (IN) field. You may be able to find relevant patents by searching for those that name a company and/or inventor who has expertise in your field of interest.

Nevertheless, while the use of fields, Boolean connectors, and wildcards can help you locate relevant patents and applications faster, many people still find it difficult to generate relevant search results.

All patents and patent applications are assigned “class numbers” by the USPTO codes that classify the patent or application into one or more very particular fields of technology, similar to the Dewey Decimal System. So if you can identify the classes of your problem or technology of interest, and then use the USPTO search engines to search documents in these classes, you’ll often find relevant documents much faster.

To identify U.S. classes for particular fields of technology, you can access the Manual of U.S. Patent Classification at Unfortunately, most users find the manual confusing and difficult to use, and it usually takes significant experience before one can quickly and accurately locate the appropriate class(es) relating to a technology in question.

By following the six easy steps I have outlined on page 80, you can bypass the manual almost entirely (or at least minimize its use) and get superior search results immediately.

Now What?

Once you’re done, you can then use the search results in your research and design efforts. In some cases, you may even be able to adopt a patented invention as an “off-the-shelf” solution. You’re usually free to use matter described in a patent so long as:

(1) The matter is not secured by this (or another) patent (i.e., the matter is not defined by the “claims” set forth at the end of a patent); or

(2) Even if the matter is covered by the claims, if the patent’s expired. Usually, patents have terms lasting 20 years from their patent application filing date, or 20 years from the date of patent issuance, whichever date is later. Both of these dates are shown on the first page of a patent. However, patents can (and often do) expire earlier for failure to pay periodic maintenance fees to the USPTO. You can check this out at the USPTO website at

Nevertheless, if you have questions about whether and how you can use certain matter, you really should get the assistance of a patent attorney. As the old saying goes, “anyone who serves as his own attorney has a fool for a client.”

Craig Fieschko has a BSME and MSME and worked for several years as an R&D engineer. He is a registered patent attorney at the DeWitt Ross & Stevens law firm, and he also teaches intellectual property law at the University of Wisconsin Law School. Request a more detailed version of the article by contacting Fieschko at, or at (608) 828-0722.

Step-by-Step Guide to Patent Searching

In this example, we look for patents related to handheld, ultrasonic surgical cutting tools

On the USPTO’s “Advanced Search” page, different fields are searchable by typing in a field code followed by a forward slash. The USPTO also provides a “Quick Search” page (not shown here), where a limited number of fields can be chosen from drop-down boxes.
Clicking “Search” will return the patent numbers and titles (or published patent applications) that match the specified terms in the specified fields. You can access the full text of a selected item by clicking on the document number or title.

Once you access the full text of a patent or application, you can get an “Image Copy” of the actual document (with drawings, etc.) either by using the “Add to Cart” option and paying to have it sent to you.
On the front page of a patent are relevant patent classes at the headings “U.S. Cl.” (U.S. Classification), listing the classes of the patent [51] and [52], and “Field of Search,” or related classes reviewed by the USPTO when granting the patent [58].

The USPTO Manual of Classification can be searched by entering terms of interest (at right) and then reviewing the resulting classes. Alternatively, you can enter a particular class (at left) and then review its description to see if it’s relevant (see figure below).
This is the “Class Schedule” resulting from entry of Class 604/22 in Figure (5), showing a description of Class 604/22 and its surrounding classes. Clicking the icon to the left of each class number will return a list of all patents in the class.

Use fielded searching in the USPTO Issued Patent search engine (not the Published Application search engine) to locate one or more “starting patents” that have strong relevance to your technology of interest. You only need one (or a handful) of starting patents. See figures above, showing an exemplary search for a handheld, ultrasonic surgical cutting tool.
“Upstream patents” are prior patents that the USPTO regarded to be technologically relevant to the starting patents. These are listed on the first pages of the starting patents under the heading “References Cited;” see the list in Figure 4 under “U.S. Patent Documents,” or in Figure 3, where the patent numbers of the upstream patents are provided as links, which allow you to quickly access their texts. Review the upstream patents and add any that are relevant to your list of starting patents. Note that only a few upstream patents are usually relevant to what you’re looking for; the remainder were cited by the USPTO because they’re relevant to some subcomponent or small feature of the starting patents.
“Downstream patents” are later patents having USPTO citations to the starting patents because the USPTO regarded the starting patents to be technologically relevant. If you’re viewing the text of a patent, you can access downstream patents by clicking the “Referenced By” link. Alternatively, you can access the search engine query box and search in the Cited References (REF) field by entering “REF/” followed by the patent number of a starting patent. Review the downstream patents, and if any are relevant, add them to your list of starting patents.
A search for further upstream and downstream patents—by returning to the second step above—can often prove fruitful. By following this process, you’re effectively building the “family tree” for the starting patents by locating patents cited in, or citing to, the growing list of starting patents.
Look at your collected starting patents and identify which classes are cited most frequently on the first page. You can then get a list of all patents in a particular class by accessing the search engine query box and searching in the U.S. Classification (CCL) field. Then review these patents and save those that are of interest (and add them to your starting patents and return to the second step above, if desired). It may also be helpful to now access the Manual of Classification and look at the descriptions of your classes of interest, as well as adjacent classes, to verify that the classes seem relevant to the technology you’re seeking.
Take your classes of interest (as well as any search strings you used for fielded searching, etc.) and search for relevant published patent applications in the USPTO Patent Application search engine. To reduce frustration, note that some fields in the USPTO Patent Search Engine are different from those in the USPTO Patent Application Search Engine, and some seemingly identical fields behave differently (with the USPTO’s “Help” link providing tips for usage).

Patent Lawyer Craig Fieschko’s Bookmarked Sites

The USPTO provides a database of issued patents, and a separate database of published patent applications. (Since it generally takes over 18 months for an application to reach issuance, published applications provide a preview of soon-to-come patents). The site allows users to search the full texts of patents from 1976 onward and patent applications from 2001 onward, and limited searching of earlier patents. Drawback: While the full texts of patents and applications are available, image copies are only printable/downloadable one page at a time unless you pay for e-mail or postal delivery of image copies.


These two websites compile full PDF image copies of U.S. patents for free, making them far easier to print and download (and Freepatentsonline allows searching as well). Or, access (not affiliated with the .org site) to pay for full PDF’s of both U.S. and European patents.

Enter a search query, and you’ll be sent regular updates of corresponding newly published U.S. patent applications.
European Patent Office

The EPO’s esp@cenet patent database allows free access to the patents of most major patenting countries, though searching is crude and image copies are printable/downloadable only one page at a time. However, by accessing “Online Public File Inspection” at under the Products and Services menu, you can download full PDF copies of European patents, provided you have the publication/application number.

One of the oldest and most powerful patent search engines, Delphion allows multiple databases (basically, all those noted above, and more) to be searched simultaneously. Disadvantage: Formerly free, now it’s pay to play.

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