4.1 Purposes of a Patent Search

Many first encounter the task of patent searching while trying to patent an invention, but there are other reasons to search for patents. Patent searching experts typically categorize patent searching by the reasons for the search, which inform the strategies and tools used. Each type of search may use a combination of strategies, which will be explained in section 4.2, and databases, explained in 4.3. The different types of patent searches fall into two rough categories, however: patent searching performed for legal reasons and patent searching performed for informational and design reasons.

Patent searching as legal research

Legal patent research typically requires exhaustivity. The end goal is to produce a set of all relevant patent literature and then determine the scope of legal coverage via analysis of the claims, terms of protection, and other details. Below are common patent search types performed to determine legal rights.

Note that patent applicants and others invested in determining the legal status of patents frequently employ professional patent searchers (including patent attorneys and agents) to conduct patent searches on their behalf, as experts can often find patent literature that novices cannot. Patent agents and attorneys can also offer interpretations of what is found. This lesson provides tips for preliminary patent searching only.

Patentability

The goal of a patentability search is to find all prior art relevant to a potentially patentable invention. The patent applicant (or patent attorney or agent) analyzes this prior art to determine if they can create a patent application that will meet the requirements of novelty and non-obviousness. Patentability searches cover granted patents and patent applications from all possible patent offices. To be thorough, the patent applicant will also search for prior art in non-patent literature using scholarly article databases and other resources. Exhaustive patentability searches are sometimes called “state-of-the-art” searches, although this term is sometimes used to describe market analyses that may not involve patentability (see below).

Freedom to operate

Freedom to operate searches help determine whether an inventor can produce and market a non-patented invention in a territory without fear of infringement. Some inventors may not intend to patent their inventions due to the cost and labor of the process or a desire to keep the technology open-source. Some inventors may initially intend to patent their inventions and, during the course of a patentability search, discover that their invention is fully anticipated by prior art and likely unpatentable. Freedom to operate searches take patentability out of the equation and focus instead on avoiding infringement. This involves asking questions surrounding the status of disqualifying prior art, for instance:

• “Are there relevant patents in the specific country or region in which I want to market my invention?”
• “Are the relevant patents still in effect, or have they expired?”
• “Was a patent ever granted for this invention, or does the disqualifying prior art appear only in applications for patents that were never granted?”

Validity/invalidity

Validity/invalidity searches establish whether another party’s patent or one or more of the patent’s claims has been granted in error. The searcher attempts to find prior art that was not acknowledged during the patent process to disqualify the granted patent. An inventor might do this to establish their own freedom to operate or to respond to an infringement suit brought by the owner of the patent.

Patent searching as informational and design research

Most prescribed patent search strategies are geared toward those interested in the legal rights afforded by patents; some experts have identified this as a result of outreach by the USPTO and other entities most interested in fostering economic growth and suggested that these strategies may not suit all patent searchers’ needs.

Patents are an underutilized and rich information resource, however, full of technical detail and, through their citations of prior art and classification systems, well-suited to following trends in history, business, and technology. Searching patent literature for informational purposes does not require exhaustivity nor as formalized an approach as a patentability, freedom to operate, or validity/invalidity search might.

Product design

Engineers and others engaged in product design can use patent literature to inform their processes. As patent literature includes new and detailed information not available in popular and scholarly sources, it can help designers:

• identify alternate solutions to problems that patented technology attempts to solve,
• better understand how a piece of technology works and might be put to a new purpose, and
• get a sense of where technology is heading in a particular field.

At the University of Wisconsin-Madison, where faculty, students, and staff are obligated to disclose new inventions (as detailed in Lesson 3 of the Introduction to Intellectual Property micro-course), having a general knowledge of patents in a discipline can also provide a baseline from which to assess whether you have an “invention” to be disclosed.

Patent searching for design ideas doesn’t need to be as exhaustive or methodical as patent searching for legal purposes. Instead, these searches may benefit from improvisation, creativity, and using databases with simple, flexible functionality. Searchers might initially borrow strategies from legal-focused searches, but find they can search more efficiently for the information needed without such a structured approach.

Historical

Needs for historical patent searching vary widely, but might involve identifying patent records for a known invention or patents invented by a specific individual or owned by a specific company. The information at hand may determine the best database and strategy in performing the search. Some factors that might influence a historical patent search include:

• Is the patent number inscribed on the invention?
• Do you know the name of the inventor or rights-holder (including name variants, e.g., was the inventor’s preferred name also their legal name, was the company that owned the rights a division of a larger company?)
• Do you know where the inventor lived and approximately when the device would have been patented?
• Do you have the device or a photo of the device?
• Do you know how the device works, what it was/is used for, and what it is made of?

State-of-the-art/landscape

State-of-the-art and landscape searches can help you understand a specific technology or market. These searches combine patent searching on a broad area of technology with accompanying searches of trade and scholarly journals, as well as industry and market research. Goals of these searches include gaining insight into the developed and as-yet-undeveloped technology in an industry, and identifying competition and market peers. Some also use the term “state-of-the-art searching” to refer to an exhaustive patentability search that incorporates non-patent literature (see above).

4.2 Patent Searching Strategies

Regardless of the type of patent search you intend to perform, you will likely need to use a strategy that combines keyword searching with other types of searches, possibly in multiple patent searching databases. The first part of this section explains some basic components you can use in a search strategy. This is followed by some combined search strategies that make use of these components.

Keywords

Most patent databases (some of which are described and linked below) allow for keyword searching, although the scope, abilities, and quirks of the search functionality can vary widely.

For instance, Google Patents is based on Google’s traditional search interface, where users start by entering keywords in a single box. Google Patents then searches a huge database of scanned patent documents from most international patent offices (in some cases back to 1791) for records in which all of the words occur anywhere within the document. This typically yields lots of results, many of which may not be relevant.

On the other hand, the USPTO Patent Public Search in ‘Advanced Search’ mode allows you to search specific fields of U.S. granted patents for keywords, but requires familiarity with Boolean operators, nested expressions, and USPTO-defined field label codes to yield good results.

As discussed in Lesson 3 regarding titles of patents, patent applicants may not use intuitive language, colloquialisms, and brand names in either their titles or descriptions. For keyword searching, instead consider the following:

• What does the invention do?
• If it’s an innovation upon existing technology, what’s novel about the approach?
• Is it a process, or is it a product?
• What is it made of?
• How is it used?
• What are some synonyms for it or other words that describe its nature?

Due to differing terminologies, different database coverages, and other factors, even expert keyword searchers will likely miss patents relevant to their search unless they follow up with additional strategies.

Inventors and assignees

One productive way to begin a search is to identify a given researcher with expertise in a type of technology, or to identify the maker of a product that closely resembles what you intend to design or patent, and to search for either the inventor name or applicant, assignee, or owner name in the appropriate field.

For some historical searches, this might be the only step required to identify the desired patent(s). For other searches, this may lead to terminology for keyword searches, cited references to explore, and classification codes to expand your search.

Forward and backward citation mining

Once you have discovered at least one relevant granted patent or patent application, you can expand your search using citations to other patent literature. Most patent searching databases include hyperlinks to patents referenced in the patent application or granted patent (with some caveats; for instance, the USPTO Patent Public Search database only links to other U.S. patents referenced, not foreign patents). Many patent databases, including The Lens, Google Patents, and Espacenet, also link from patent documents to later patent applications and granted patents that referenced them as prior art.

Classification searching

As explained in Lesson 3, patent examiners assign classification codes to patent documents so that similar inventions are grouped together even if the inventors used different terminology when filing their applications.

Cooperative Patent Classification (CPC) is a single system used by the U.S. Patent and Trademark Office and the European Patent Office (EPO) to classify patents and is compatible with the International Patent Classification system used more broadly. Examiners typically assign multiple CPC codes to a single patent.

Each CPC can be broken down by levels of specificity. For example:

A63F 9/16
Section A (HEALTH; AMUSEMENT)
Class 63 (SPORTS; GAMES; AMUSEMENTS)
Subclass F (CARD, BOARD, OR ROULETTE GAMES; INDOOR GAMES USING SMALL MOVING PLAYING BODIES; VIDEO GAMES; GAMES NOT OTHERWISE PROVIDED FOR)
Group 9 (Games not otherwise provided for)
Main group 16 (Spinning-top games)

Augmenting a keyword search with CPC searching may seem like extra work, but patent examiners make heavy use of these codes in their prior art searching, which means that learning to use CPC codes in the patent search process can help you navigate the literature on their terms. Understanding and using CPC is essential for patentability, freedom to operate, and validity/invalidity searches, but can also helpfully define the scope of a technology for a state of the art or landscape search, and can also unearth invaluable patent literature for the design process.

One way to get to know the CPC system is to experiment with Espacenet’s Classification Search feature, which allows you to search on keywords within the classification definitions and to navigate through the levels of classification by clicking headings, starting with lettered Sections at the top level. An advantage of viewing CPC codes in this way is that you can see neighboring classifications, which may turn out to be just as relevant or even more relevant for your search.

Combined search strategies

As mentioned above, most search strategies are oriented toward establishing legality–they emphasize a systematic, consistent approach geared toward comprehensiveness. Patent researchers engaged in less formalized product design, state-of-the-art/landscape, and historical patent searching may find that harvesting these strategies for parts and using multiple patent searching databases in tandem may be more productive than following them strictly. Below are just a few examples.

Classification first, keywords second

In some cases, you can effectively begin your search by locating relevant CPC codes in the classification searches on Espacenet or the Lens using keywords that apply to the broad area of technology. You can then search a patent database using the appropriate CPC code. Because some CPC classes are assigned to hundreds or thousands of patent documents, you will likely need to refine your search by adding more specific keywords to the search. For instance, you could begin a search on the CPC A63F9/16, which includes all spinning top games (nearly 1,000 international patent records). To narrow your search to inventions that function like the fidget spinner, you could combine a CPC search with a keyword search on “ball bearing” or “weights”.

Keyword searching first, classification second

As classification scheme definitions are developed around consistent terminology, starting with classification will only yield good results for searchers who luck into using the same terminology as the creators of the scheme.

A way around this is to use brainstormed keywords to search patent literature directly by running searches in databases with full-text access to lots of patents. Once you have found records for a few relevant patents, you can use the CPC codes assigned to those patents to expand the search to include granted patents and patent applications in which different terminology is used to address the same functionality.

For instance, you might try one of the following methods:

• Begin by using a keyword search in Google Patents, which tends to return many results from U.S. and international patents, but does not have a well-developed classification search. Then create a list of CPC codes from Google Patents, locate them in Espacenet’s classification search, then search for all patents for those classifications.
• Alternatively, run a keyword search in The Lens then use The Lens’s built-in classification search to expand. For each relevant granted patent or patent application, follow up on inventors, applicants/owners/assignees, and backward and forward citations.

In all cases, the key to patent searching is repeating the process, trying new keywords, new classifications, and combinations and, typically, using a combination of patent searching databases.

Patent number, owner, or inventor first

Some patent searchers may begin their search with specific information about a patented invention, patent owner, or inventor. When you start with this information, it can sometimes save you the time in developing keyword strategies. Instead, use the known information to begin your search. As long as you can find one record for a granted patent or patent application, you can use it to find relevant CPC codes for additional searches, cited prior art, and, depending on the database you use, later patent literature that cited the record as prior art.

4.3 Databases

No single patent searching database does everything well. The databases created by the USPTO, EPO, and other patent offices have the most definitive information for those offices; however, third-party databases offer unique search features, user-friendly interfaces, and even full-text searching on patent literature that the official patent office databases may not. Each patent searching website may visualize the information associated with a patent document differently (and may include updated information on details that may change after issuance, such as assignee), but most also include downloadable PDFs of the original patent document.

Below is a list of useful patent-searching databases and a brief summary of their content and capabilities as of 2024. Although there are subscription patent searching databases available, the databases below are all free to the public.

USPTO website databases

The USPTO website includes several patent searching databases. These offer definite, official information on U.S. patents and patent applications; however, each database is dedicated to a particular aspect of patent protection (i.e., patent literature, the application process, or patent assignee status and history).

European Patent Office patent search

Espacenet is the official EPO patent search database and includes patent literature from patent offices throughout the world, including the U.S.

Third-party patent searching websites

There are a number of third-party patent searching websites developed by corporations and non-profit entities. Two of the most user-friendly and useful are The Lens and Google Patents.

4.4 Searching for Design and Plant Patents

As U.S. design patents and plant patents do not map directly to patents in other countries and regions, searchers for these types of patents may require different strategies.

Design patents

U.S. design patents are searchable on the USPTO websites. The USPTO does not classify design patents using the CPC system, but rather continues to classify them under the older U.S. classification system. One recommended strategy is as follows:

1. Locate the appropriate class code (D1-D99) for the subject matter in the design patent classes listed on the USPTO site.
2. On the Classification Symbol Lookup screen, choose USPC, type the design class code in the Enter Classification symbol field, and click Submit.
3. From the page of classification subclasses, click on a relevant subclass number to read a definition of the subclass. NOTE: Subclasses in black and all-caps indicate that they include the subclasses directly beneath them, thus, in class D17 for musical instruments, subclass 10 for WIND INSTRUMENT also includes subclasses 11 for cornet or trumpet, 12 for harmonica, and 13 for element or attached. The more specific you can be in determining subclass, the fewer patents you’ll have to read through.
4. Click the red outlined P next to the desired subclass. This will return a list of granted U.S. patents assigned this subclass.

U.S. design patents are also available in Google Patents and The Lens and will be included in search results for keyword searches. Searchers can limit their results to U.S. design patents on Google Patents by selecting “Design” as the Type. Searchers can limit their results to international design rights (including U.S. design patents) by selecting Design Right as the Doc Type. The Lens also includes U.S. Classification as a filter, which can be used to limit to specific U.S. design patent classification codes.

Searchers can also use the WIPO Global Design Database, which includes U.S. design patents, as well as comparable industrial design rights from other countries.

Plant patents

Like design patents, U.S. plant patents are searchable on the USPTO website. As is not the case with design patents, the USPTO classifies plant patents using both the CPC system and the older U.S. classification system. Using the U.S. classification system may yield better results for plant patent searchers.

1. Start on this list of subclasses for the U.S. class PLT, which is assigned to all plant patents.
2. From the page of classification subclasses, click on a relevant subclass number to read a definition of the subclass. NOTE: Subclasses in black and all-caps indicate that they include the subclasses directly beneath them, thus subclass 152 for NUT (INCLUDING ORNAMENTAL VARIETY) also includes subclasses 153 for Pecan, 154 for Walnut, and 155 for Almond. The more specific you can be in determining subclass, the fewer patents you’ll have to read through.
3. On the subclass explanation screen, click the red outlined P next to the desired subclass. This will return a list of granted U.S. patents assigned this subclass.

As mentioned in Lesson 3, U.S. plant patents often contain color photographs in the Drawing Sheets section in order to best represent the appearance of the plant. These are only available in black and white via the USPTO website and most other patent databases; however, current full-color print versions are made available at Patent & Trademark Resource Centers, including Steenbock Library. In addition, the University of Maryland Library and New York Public Library have scanned and made available online many full-color plant patent images.

For more information on U.S. intellectual property protection on agricultural products, refer to the website for the U.S. Department of Agriculture’s Seed Liaison program.

4.5 Lesson Review