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Patent and Trademark Resource Center: Patent Search Assistance

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The best place to start is by watching the video below.

Then use the Strategy Guide and Workbook to aid in conducting a patent search. You can either print out the PDF below, or step through the online version (available just below the PDF link). 

7-Step U.S. Patent Search Strategy

Searching for U.S. Patents on the Internet

The website of the U.S. Patent and Trademarks Office offers all the tools necessary to do a comprehensive search for previously issued U.S. patents, from 1790-present. The website contains a database of the images and drawings for all issued patents back to 1790, and keyword searchable full-text back to 1976. 

Please review the following limitations of patent searching on the Internet before proceeding with this step-by-step guide:  

  • A patent search is not an easy task to do.
    If you are an inventor who will make decisions based on the results of a patent search, it is important to consider whether you want to attempt to do a patent search yourself. A thorough search could take many hours. You may want to consider hiring a patent attorney or a patent search firm. To perform a prior art search, the following research tools should be investigated: 

    • U.S. and foreign patent databases;

    • Databases that contain journal articles and technical or government reports for the relevant subject area. You will want to utilize databases on the list of databases available statewide in Maine. These databases are made available by the Maine State Library and the Maine State Legislature;

    • Internet search engines;

    • Maine's Science, Technology and Business Portal for information on a wide variety of internet resources;

    • Company and product catalogs.

  • Searching patents that contain a specific word(s) almost guarantees that a searcher will miss several patents of interest.  Here's why:

    • You will miss patents of interest that do NOT contain your search term(s). There are many ways to describe the same product or technology. Especially searching by title is not recommended because patent titles are often very short and not descriptive. It is difficult to assemble a comprehensive list of all synonyms and keywords.

    • You will miss patents of interest that were issued before 1976. Only patents issued after 1976 are searchable by keywords from the title, abstract and entire patent. You can also not search by inventor and company name before 1976.

  • For more information on the limitations of the U.S. Patent and Trademark Office's Web Patent Database see their Important Notices page.

Patent Search Assistance

Patent and Trademark Resource Center (PTRC) staff are available to provide training on patent search processes and research tools including PubEAST, PubWEST,† and the USPTO website. Additional information is available through the USPTO website at, by phone at 1-800-786-9199, or by e-mail at For legal matters, contact an attorney or agent registered to practice before the USPTO at

Preliminary U.S. Patent Search vs. Comprehensive Prior Art Search

This step by step guide provides a strategy for searching U.S. patents to locate and evaluate relevant prior art (earlier patents and published patent applications). A comprehensive search would also include foreign patents and non-patent literature (newspapers, magazines, dissertations, conference proceedings, and websites). PTRC staff can provide training on how to locate these additional resources.

Search Preparation and Documentation

Plan on spending a few hours learning the search process and additional hours for searching and evaluating results. The length of time depends on the complexity of the invention. Careful recording of the search process, including the databases used, date and time of search, classes searched, and patent and application numbers retrieved, is an important part of effective searching.

The Value of a Patent Search

In order for an invention to be patented, it must be sufficiently new or different from what has already been issued or published. In patent jargon, this is called "novelty".  A thorough patent search will help an inventor assess the novelty of his or her idea. These searches are referred to as 'prior art searches.' Prior art searches may be conducted by the inventor, a patent searching company, a patent agent or a patent attorney. The PTRC will assist inventors in beginning a prior art search.

Here are some reasons why inventors should do a preliminary patent search before taking steps towards applying for a patent or hiring an attorney:

Reason 1: If the search results indicate that an idea has already been patented, then you will save the time, effort, and money involved in submitting a patent application and starting the licensing or marketing process. A product may have been patented but never have made it to the marketplace. Only 2 percent of all patents are ever commercialized. This is why inventors familiar with products or technology in a particular area may be surprised by the results of a patent search. Also the patent application fees are nonrefundable! If your application is rejected you lose the fees paid.

Reason 2: The results from the patent search may provide new inspiration and ideas for the inventor. Perhaps there is something already patented that you can improve upon. There must be novel, non-obvious improvements or changes to existing products or patents to meet the standard for a new patent. You can also refine your invention and patent application so that it does not interfere or overlap with existing patents.

Reason 3: By doing a patent search, you become more informed about the strengths of your invention and the current "state of the art," resulting in a stronger patent application or a more reasonable decision on whether to proceed with the patent process. You also become aware of companies that own patents in your area of technology. The patent search can be expanded by searching on relevant companies and looking at their full list of patents. You may decide to contact some of these companies about licensing and manufacturing your invention. You may also discover that similar inventions were not commercially viable or profitable. This may help you make a decision about whether it will be practical to continue with the patent process.

Reason 4: The search will identify patents and articles that are related to your invention. It is important to read over these to become informed about the elements required for a patent. These articles and prior patents may also comprise the list of prior art that is included with most patents.  Also if certain components of your invention have been described in detail in prior patents or articles these may be used in your application in place of detailed drawings and description that you would have to provide. This will save time and money in the preparation of your application. The knowledge from all of your searching and reading will make your patent application stronger and less vulnerable to rejection by the USPTO and challenges by other patent owners or companies.

Reason 5: If you use the services of a patent attorney, the knowledge gained from the search will help you become a more informed client. Many patent attorneys advise potential clients to perform their own preliminary patent searches, often as an attempt to "weed out" all but the most serious inquiries.

Brainstorm Terms Describing Your Invention

Begin by writing down a brief, accurate description of the invention. Avoid overly broad and generic terms such as "device," "process" and "system." Consider synonyms for the terms you initially select. Note important keywords and technical terms. Use the following questions to help identify keywords and concepts. 

  • What is the purpose of the invention? Is it a utilitarian device or an ornamental design?
  • Is the invention a process – a way of making something or performing a function – or is it a product?
  • What is the invention made of? What is the physical composition of the invention?
  • How is the invention used?
  • What are keywords and technical terms that describe the nature of the invention? Consult a technical dictionary or thesaurus to help find the appropriate terms.

Let's say we invented an umbrella with a new rib design to eliminate the umbrella collapsing or inverting due to winds. Answers to the questions above might look like this:

  • Purpose: Umbrella has a new rib design to eliminate an umbrella collapsing or inverting due to high winds. 
  • Invention: An improvement in umbrellas to eliminate need for frequent replacement of umbrellas. 
  • Invention Components: Framework with ribs, stretchers and a main frame, securing rings, mounting brackets, joint connectors, fabric connectors, fabric, linkage bar. 
  • How used: As needed in protection from the elements. 
  • Other terms (in addition to above): Parasol, sunshade, support or assembly apparatus, windproof, wind-resistant.

Access and Review Cooperative Patent Classification Schema Using USPTO's Website Site Search Feature

  • The USPTO home page ( has a Site Search text box in the top right corner. CPC classification schema (class schedules) can be searching using this box. Use specific language for your search terms, such as CPC scheme umbrella. Typing in simply umbrella would be too broad and provide too many unrelated results. Site Search text box.

  • From the Search Results page, click on an entry for a Class-Subclass Scheme page. If you are not satisfied with the search results, rerun your search using synonyms you identified in Step 1 for your invention. Site Search Results 

  • Scan the classification titles in the class scheme for A45B looking for the most relevant classification. Dot indents are used to show hierarchical relationships in the scheme. The more dots the more specific the concept is. Some titles may have references in parenthesis following the title that can aid in the classification selection. We find A45B 25/22 as a possible good match based on the title "Devices for increasing the resistance of umbrellas to wind." There is nothing under A45B 25/22 with two dots that is more specific, so this may be a good choice. 

Class-Subclass Scheme titles



Review Classification Definition Linked to the CPC Classification You Selected

If the selected classification title is underlined, it is hyperlinked to a CPC Classification Definition. CPC Classification Definitions are helpful in establishing the scope of the relevant classification and thus ensuring you have selected the most relevant classification. The definitions may include important search notes and suggestions for further searching. In this example, we click on A45B 25/22 and get the following definition, which is unusual in that it relies solely on images (most CPC definitions use text).

Definition statement for A45B 25/22

Retrieve and Review Issued Patents Using the CPC Classification You Selected

Having identified a relevant CPC classification, use the CPC classification to retrieve and review all the U.S. patents currently assigned to the CPC classification in the PatFT (Patents Full-Text and Image) database on the USPTO website. On the USPTO home page (, select "PatFT" under the drop-down "Quick Links" menu. Quick Links

Enter the CPC classification in Term 1 Box (Important: Delete the space in the middle of any CPC classification when doing a PatFT search, so enter A45B25/22".). In the Field 1 drop down box select "Current CPC Classification." Leave the Term 2 Box blank. For Select Years, use the drop down box to select "1790 to present [entire database]". Click on the Search button to get results. 

PatFT search box

Click on either the patent number or the patent title to see the full-text of the patent (patents issued prior to 1970 will not have a full-text version, only a limited text entry). Review the front page of each patent in the Results List, paying special attention to the abstract and representative drawing. Jot down the number of those patents you feel are similar to your invention that will merit later closer review. 

Results of PatFT search

Click on the red "Images" button at the top of the page to veiw a pdf image of the patent. 

PatFT Example Patent


Conduct In-Depth Review of Patents You Selected Based on Their Front-Page Information

Using this selected set of most relevant U.S. patents, now review each on in-depth for similarity to your own invention, paying close attention to the other sections of the patent--additional drawing pages, the specification and especially the claims. References cited by the applicant and/or patent examiner may lead you to additional relevant patents. Remeber the claims constitute the boundaries of legal property rights given to the patent holder. Print or download copies of the most relevant U.S. patents you find.

Full Text Patent

Retrieve and Review Published Patent Applications Using the CPC Classifications You Identified

Use the CPC classification you selected in Step 3 to retrieve and review all the U.S. published  patent applications currently assigned to that CPC classification in the AppFT (Applications Full-Text and Image) database on the USPTO website. On the USPTO home page (, select "AppFT" under the drop-down "Quick Links" menu. AppFT

Enter the CPC classification in Term 1 Box (Important: Delete the space in the middle of any CPC classification when doing an AppFT search, so enter "A45B25/22".). In the Field 1 drop down box select "Current CPC Classification." Leave the Term 2 Box blank. For Select Years, you can only select "2001-present" since the U.S. has only been publishing applications since 2001. Click on the Search button to get results. 

AppFT search box

As you did in Step 4 with your Patent Results List, click on either the published patent application number or its title to see the full-text version. Click on the blue "Images" button at the top of the page to view a pdf image of the published application. Review the front page of each published patent application, paying special attention to the abstract and representative drawing. Jot down the number of those published patent applications you feel are similar to your invention. 

AppFT sample search results

Using this selected set of most relevant U.S. published patent applications, now review each one in-depth for similarity to your own invention, paying close attention to the other section of the published application--additional drawing pages, the specification and especially the claims,. Print or download copies of the most relevant U.S. published patent application to your inventions. 


Options for Broadening Your Search

Having completed a preliminary U.S. Patent and Published Patent Applications search in which you did not find publications that disclosed what you hope to protect in your own patent application, you have several options to broaden your search--based on available time and resources. 

  1. You can supplement you CPC classification search in the PatFT and AppFT databases by using Keywords to search. A Keyword search may simply turn up documents that were not well classified or perhaps had classifications you missed in your review of CPC schema in Step 2. U.S. patent examiners regularly supplement their classification search with keyword searches. Group (using "OR") together synonyms and especially consider the use of technical engineering language rather than common everyday words, e.g., (car or automobile or auto or "land motor vehicle"). Use truncation symbols to get singular and plural versions of a word (airbag$). Use quotes to group search phrases where words are adjacent ("image viewer").
  2. Broaden your search with U.S. Patent Classification (USPC). While U.S. Patent Classification ended being used on U.S. utility patents on 1/1/2015, the classification system remains searchable for all pre-2015 U.S. utility patents. If you found relevant U.S. patents or published patent applications using CPC, note their current U.S. Patent Classifications in their html version. You can then run a USPC search in PatFT (and separately in AppFT) while eliminating (using Boolean operator "NOT") the publications you previously saw using CPC so you don't have to review any of the same publications again. Your PTRC librarian can show you how to use USPC and Boolean Operators.
  3. Extend your search to foreign patents and published patent applications using the CPC classification you identified in Step 3. Re-run your search using Espacenet (, the European Patent Office's worldwide patent publication database of over 90 million patent applications. Your PTRC librarian can show you how to search Espacenet.
  4. Since inventions can be publicly disclosed in a variety of non-patent print and electronic publications, you can choose to search books, journals, websites, technical catalogs and conference proceedings as well. Possible sources to consult include:


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Notes and Disclaimer

PubEAST and PubWEST are available at Patent and Trademark Resource Center libraries:

Disclaimer: The information contained in this guide is not intended as a substitute for professional legal advice. Use it as a general guide for conducting a preliminary patent search. The USPTO recommends that inventors consult a registered patent agent or attorney prior to filing an application.

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