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Zimmerman's Research Guide


Patents - U.S.

This entry is divided into the following sections -

For patents registered in other countries, see the separate entry for "Patents - Foreign."

A. Getting U.S. Patents

Following are the sources I know for searching and retrieving U.S. patents.

US PTO: The USPTO's Pat FT database contains all US patents issued since 1790. You can search the full text of patents issued since 1976. You can search for older patents by patent number, issue date and classification. Pat FT is free and works well for many patent-related requests, although the free and fee-based commercial databases generally provide better searching, printing and other value-added features. Patent Surf provides a natural language interface for searching and retrieving patents from the US PTO database.

Other Free On line Databases: Goggle Patents, FreePatentsOnline and ArchPatent let you search and retrieve the full text of patents. Patent Fetcher lets you pull PDF patents by number. The InventBlog's Guide to Downloading Patent Copies discusses various free patent databases. The Intellogist allows you to create a comparison chart of the major free (and fee-based) patent databases (free registration required).

Fee-Based Patent Research Systems Leading fee-based patent research systems include PatBase by minesoft, Orbit by Questel, Thomson Innovation by Thomson Reuters and TotalPatent by LexisNexis. Other systems include Reedfax, GetThePatent, Delphion, STN, Westlaw, ProQuest Dialog, Bloomberg Law and Lexis. (Note: If you have the patent number, you can pull U.S. patents on Lexis or Westlaw using the format, "patno ______".)

The Intellogist allows you to create a comparison chart of the major fee-based (and free) patent research and document retrieval systems (free registration required). More patent research and document retrieval systems are listed by the Patent Information Users Group.

Document Retrieval Services: Document retrieval services will send someone to the US PTO to make a photocopy of the patent and any related materials. Services include Research Solutions, Landon IP (703-486-1150) and Thomson Reuters' Scientific (800-223-9697). More services are listed by the Patent Information Users Group.

For retrieving IP-related books and articles, both Independence Legal Support (240-392-0017 or requests@independencelegalsupport.com) and UDI / Urgent Documents International (docs@udi-usa.com or 510-524-4351) come highly recommended.

Depository Libraries: Libraries participating in the Patent and Trademark Depository Library Program have patents going back anywhere from a few years to a few hundred years and, if you're nearby, you can always drop by to make copies. A list of these PTDLP Libraries is posted at www.uspto.gov/go/ptdl/ptdlib_1.html.

B. Other Patent-Related Issues


For patent arbitration rules or awards, see the "Arbitration" entry.


The U.S. PTO would prefer not publish patents until they are issued, however, many foreign countries publish patent applications after 18 months, even if they aren't yet issued. As such, the PTO publishes U.S.patent applications after 18 months if they will also be published abroad. The PTO started publishing applications in 2002 (specifically starting with "patent applications filed on or after November 29, 2000 eighteen months after the effective filing date of the application").

The PTO has a database called AppFT for published applications and another called Public PAIR for both published applications and "and applications to which a patented or published application claims domestic priority." There is also a Private PAIR database to track unpublished application, but access is restricted to the inventor/owner and the attorney-of-record.

You can search for the publicly available applications in all the commercial databases. Alternatively, you can try to find applications simultaneously published overseas by searching for a foreign application and then looking at the patent family. Patent "families" are discussed below. See "Patents - Foreign" for information about international patent searching.

If you can't bring up an application in the Public Pair system, you can ask the PTO's Patent Electronic Business Center (866-217-9197 or EBC@uspto.gov) to confirm if you have the correct information. They can't give you information about the status of the application, but they have confirmed for me that my application names and numbers correspond to pending, unpublished applications.

Provisional Applications: Provisional applications count as an earliest filing date but don't trigger the 20-year patent term. Some commercial databases allow you to search specifically for provisional applications. For more information, see the USPTO's Provisional Application for a Patent page.

Monitoring Applications: I haven't tried them, but I hear you can monitor patent applications with Reedfax Pair-Pal, Cardinal IP Pair Alerts, MaxVal Pair Alerts and ceStatus.

Assignments and Reassignments

Although patent owners are not required to notify the USPTO when a patent is assigned (or reassigned), most assignments are reported.

The most up-to-date source for this information is the USPTO'S Assignments database. You can also get reassignment information through Lexis (just pull the patent -- Lexis integrates subsequent data into its patent records), Bloomberg Law, the IFI Claims US Patents & Legal Status database on ProQuest Dialog, STN (IFICLS), Thomson Innovation and probably other search systems. Note: The data from these sources does not always match so, when certainty is essential, you may want to do follow-up research.

For follow-up research, call a patent research company (for sources, see the Prior Art Research section, below). When you call, be sure to specify whether you need copies of any assignment instruments noted in the record.


If you need briefs from a particular court case, you can retrieve copies from the court clerk, PACER, Courtlink or one of the other online systems discussed in the "Docket Sheets" entry. If you need briefs from a case before the US PTO, you can find them in the file history (see the "File History" section, below). If you need sample briefs, you could search through briefs filed in patent cases with Federal courts using Courtlink or try the Federal Patent Briefs database on Westlaw (FPT-BRIEF).

Classification Systems

The U.S. developed its own classification system for categorizing utility patents in 1836. The U.S. Patent Classification (USPC) was continuously revised until November 2010. On January 1, 2013 the US PTO began using the Cooperative Patent Classification (CPC) system for published utility patent applications. In January 2015 the US PTO is scheduled to use the CPC for granted utility patents as well as published applications.

The U.S. also has classification systems for design patents and plant patents, which are not affected by the adoption of the CPC.

Demand Letters

Demand Letters are generally sent by a patent holder to a party who is allegely infringing on the patent. The letter generally "demands" a payment for using the patent coupled with a threat to sue if the payment is not made. You can find many Demand Letters posted on Trolling Effects. You can compare one demand letter to others using Demand Letter Analytics by Lex Machina.


A patent "family" is a list of the countries where a patent was filed, plus the number assigned to the patent by each country's patent agency.

INPADOC patent families are produced by the European Patent Office. You can get the INPADOC family for free by pulling up the patent record in the EPO's esp@cenet and clicking on "View INPADOC patent family" in the left navigation bar. INPADOC families are also available through all the major commercial online patent research systems. For more information about INPADOC patent families, see the The "extended" (INPADOC) patent family page.

Derwent patent families are produced privately and are available through the various patent systems owned by Thomson Reuters including Thomson Innovation, ProQuest Dialog, Delphion and Westlaw.

Qweb provides INPADOC families plus two proprietary families - PatPlus and the well-reviewed FamPat, which provides tighter families of more closely related patents.

For more information about INPADOC, Derwent and other patent families, see the discussion of Patent Families on the Intellogist.

Research tip: INPADOC and Derwent each provide good family information; for best results, search both.

Caveat: If you are using INPADOC patent families through a commercial service, be sure their INPADOC database is current.

File Histories

File histories (also called "file wrappers") contain the communications between the US PTO and the agent or attorney filing the patent. You can get copies for patent applications opened to the public since June 28, 2003 by searching on the application number in the Public PAIR database and then clicking on the "Image File Wrapper Tab." Search the Patent Application Full Text and Image Database if you need to look up an application number. To search through file histories themselves, use the file history database on Westlaw, which include documents submitted since 2001.

Older file histories can be copied at the US PTO. Several services specialize in retrieving file histories including The Patent Bank, DigiPat, Thomson File Histories (800-445-9760 or 800-223-9697), Reedfax (800-772-8368), LexisNexis, Landon IP (703-486-1150) and metroPatent. You can also order file histories through some of the online research services, including QPat and Thomson Innovation. More services are listed by the Patent Information Users Group and in File Wrappers? Are Those, Like, People Who Bust a Wicked Rhyme About Paperwork? by Anne N. Barker.

For more about file histories and why they are useful, see the File Wrappers? article, mentioned above.

Interference Cases

An inventor or other party that wants to claim they invented something before the patent holder of recored can file a petition with the USPTO's Patent Trial and Appeal Board or PTAB (formerly known as the Board of Patent Appeals and Interferences until September 16, 2012). Documents filed in patent interference proceedings can be pulled free through the PTO's Final Decisions and the Interferences databases. You can search filings on Westlaw (BPAI-FILINGS). For more about the Board, see "Patent Trial and Appeal Board (PTAB)," below.

Legal Status

A patent's "legal status" tells you whether it is effective or not. Key legal status "actions" include the filing of an application and the grant of a patent, which are necessary for the patent to take effect. On the other hand, a patent application can be denied or withdrawn, which usually prevent a patent from taking effect.

The EPO's INPADOC legal status data file is the leading source for legal status information. INPADOC legal status data is gathered from the USPTO and the patent offices of other countries. INPADOC legal status data is available from just about all the fee-based research systems discussed above. Some systems, such as Micropatent, supplement INPADOC legal status data with their own feeds from the US PTO (and other national patent offices) and therefore can make new data available faster.

Post-Issuance Information There are many post-issuance actions that can affect the legal status of a patent. For example, a patent may be be reexamined, reissued or become inactive if the maintenance fee isn't paid. The USPTO lets you look up Expired Patents for Failure to Pay Maintenance Fees by patent number or application number. To check whether a patent has been reexamined, first search for the patent number on PAIR, then select the tab for "Continuity Data." Under "Child Continuity Data," if the serial numbers for any of the patents listed begins with a 90 or 95, then the patent has been reexamined. Fee-based research systems that provide both INPADOC and post-issuance information include Thomson Innovation, the IFI Claims US Patents & Legal Legal Status database on ProQuest Dialog and STN (IFICLS).

Other sorts of post-issuance information are discussed in the Assignments and Reassignments section, above, and the Litigation section, below.


The Patent Act of 1790 (Ch. 7, 1 Stat. 109-112) was the first U.S. patent law. It provided for registration but not examination of patents. The 1790 Act was replaced by the Patent Act of 1836 (Ch. 357, 5 Stat. 117), which established the U.S. system of patent examination. The Patent Act of 1952 (Ch. 950, P.L. 82-593, 66 Stat. 792) made substantial changes to the law. The Leahy-Smith America Invents Act (PL 112-29) made additional changes, most notably switching the test for the grant of a patent from "first to invent" to "first to file."

The Franklin Pierce IP Mall posts the text, legislative history materials and commentary for the Patent Act of 1952, as well as checklists of the legislative history materials for all patent laws passed from 1969 to 1988. For an excellent analysis of the legislative history of the Leahy-Smith America Invents Act (PL 112-29) see Joe Matal, A Guide To The Legislative History of the America Invents Act: Part I of II, 21 Fed. Cir. B. J. 435 (2012) and A Guide To The Legislative History of the America Invents Act: Part II of II, 21 Fed. Cir. B. J. 539 (2012).


There is no perfect way to identify and track patent litigation, but there are a few tools available, notably Derwent's LitAlert database (ProQuest Dialog or Westlaw), the special "Patent Search" on CourtLink, Docket Navigator and LexMachina. STN, TotalPatent, Thomson Innovation, and Qweb also have litalert databases. You can also search the PACER Case Locator using the Nature of Suit (NOS) code 830 ("Patents") under the "Civil" cases tab.

You can search for patent litigation by patent number using CourtLink, Docket Navigator, and Bloomberg Law . As an additional check, you may also want to run the patent number through a dockets database and/or a case database.

In addition, you can Shepardize a patent on Lexis to find published opinions -- or just search the patent number in any appropriate Federal cases database. Also, you can search the owner or assignee's name in PACER's U.S. Party Index or another docket search service (see "Docket Sheets"). For public companies the litigation might be mentioned in an SEC filing (see the Filings section of "Securities and Exchange Commission"). You could also search news databases on Lexis and/or Westlaw and/or the Federal Patent Briefs database on Westlaw (FPT-BRIEF).

Alternatively you can KeyCite a patent on Westlaw using the format: "US pat no _____". The KeyCite will reference published opinions as well as assignments, citations in later patents and references to litigation from Derwent's LitAlert. This saves the cost of searching the Westlaw databases if there are no opinions or no LitAlert cases.

ITC Investigations: The International Trade Commission is authorized to investigate claims of patent or trademark infringement (also trade secrets, false advertising, etc.) under Section 337 of the Tariff Act of 1930. If ITC investigations are of interest, be sure you use a research system that includes ITC actions. EDIS is the ITC's system for filing and retrieving documents; you can use if for basic searching. For better searching, nicer looking results, and alerts, use Docket Navigator, Docket Alarm, Bloomberg Law or Courtlink which all cover ITC patent infringement investigations, in addition to litigation in U.S. courts. Westlaw also has opinions and documents from ITC cases (FINT-ITC). Treatises discussing 337 cases include Unfair Competition and the ITC: A Treatise on Section 337 Actions (West) and A Lawyer's Guide to Section 337 Investigations Before the U.S. International Trade Commission (ABA).

Patent Trial & Appeal Board (PTAB) Cases: You can search for PTAB cases using Docket Navigator or Docket Alarm.

Markman Orders and Markman Hearings

A "Markman Order" - also known as a claims construction order - establishes the meaning of one or more patent claim terms disputed by the parties to a lawsuit. Markman Orders are available on PACER, CourtLink and other Federal docket search systems. Markman Orders may be included in some U.S. District Court opinion databases. Westlaw has a database just for Markman Orders issued since 2000 (MARKMAN-ORDERS). The "Tools & Resources" section of WestlawNext includes a Markman Construed Terms Index that "allows researchers to browse words defined in Markman documents. Researchers can browse the index, click on the desired terms, and quickly pull the Markman documents defining those terms."

Markman Orders take their name from a case called Markman v. Westview Instruments, 517 U.S. 370 (1996), which held that disagreements over the meaning of terms used in patent claims should be decided by judges. These disagreements are now heard in pre-trial "Markman hearings," and the judge's decision is called a "Markman Order."

Patent Claim Construction and Markman Hearings (PLI) is "a succinct guide to both claim construction and the special procedures that have evolved to accomplish such construction."

Patent Term Calculator

The expiration date of a patent depends on several factors. The PTO's Patent Term Calculator is designed to help you figure it out.

Patent Trial and Appeal Board (PTAB)

The Patent Trial and Appeal Board is a division of the PTO designed to hear challenges to whether a patent was properly issued. It was created by Congress in 2011 as a successor to the Board of Patent Appeals and Interferences (BPAI) and started working in September 2012. It is a popular venue for companies defending patent interference claims in other courts; companies can effectively defeat the interference claim by showing that the other party's patent was not valid to begin with.

For information about the Board, see the PTAB website, which includes a helpful Trial Practice Guide.

Documents filed in PTAB proceedings can be pulled free through the PTO's Final Decisions and the Interferences databases. Or you can use commercial services such as Docket Navigator, Docket Alarm or Westlaw.

For docket alerts and tracking, use Docket Navigator. The Bloomberg BNA PTAB Challenge Navigator (part of the Intellectual Property Law Resource Center) provides searchable, indexed summaries of PTAB cases. You can search PTAB case filings on Westlaw (BPAI-FILINGS) and Docket Navigator.

PTAB decisions are searchable on Lexis (with BPAI decisions back to 1928), BNA (with BPAI decisions back to 1929) and Bloomberg Law.

Prior Art Research

You can do good basic research using the databases discussed in the "Getting U.S. Patents" section, above. However, a full search to see if a patent is viable (e.g., not "obvious" or "anticipated") requires searching the full range of "prior art," and that is a more complicated matter.

You can get the basics of prior art research from tutorials such as Finding Prior Art for an Issued Patent posted by PubPat. More advanced information is available in the Best Practices section of the Intellogist wiki. Useful tools for different kinds of prior art research are referenced in the Intellogist's Resource Finder. Qweb provides substantial non-patent literature to facilitate prior art research.

For more information (a) check out a treatise on intellectual property research, (b) find out a helpful librarian or paralegal who specializes in IP research, and/or (c) hire a patent research service to do the job for you. If you don't have a favorite search service, check the List of Patent Search Firms provided in a 2010 presentation hosted by the PLL/SIS Intellectual Property Librarians' Caucus or the list of Patent Information Vendor Sites posted by the Patent Information Users Group.


You can Shepardize a patent on Lexis to find other patents and cases that relate to your patent. The format for Shepardizing a patent is "patno ______" (without the quote marks). You can KeyCite a patent on Westlaw using the same format.

See also the "Families" and "Litigation" sections above in this entry, and the separate entry on "Shepardizing."


Most of the major patent law treatises are listed and reviewed in Kendall Svengalis' Legal Information Buyer's Guide and Reference Manual (New England LawPress). The most well-known treatise in the field is Chisum On Patents which is available in print and on Lexis.

The Thesaurus of Claim Construction tells you how hundreds (thousands?) of terms used in patent claims have been interpreted by the courts and other sources.

The US PTO posts the current Manual of Patent Examining Procedure (MPEP). Historical editions of the MPEP back to the original 1948 edition are available from the USPTO website. For better searching, historical editions are also available through HeinOnline. To locate print copies of old MPEP's check WorldCat. The MPEP is republished with additional forms, commentary and practice tips in the Practitioner's Manual of Patent Examining Procedure (West).

{Thanks to Hillary Rubin, DCO head librarian at Kenyon & Kenyon LLP, for reviewing this entry in May 2010 and adding several useful resources. Any mistakes since then are mine alone. AZ}

See Also
Arbitration, Mediation and Alternative Dispute Resolution
Patents - Foreign
Patent Cooperation Treaty
Patent Insurance
United States Court of Appeals for the Federal Circuit

For comments, questions and suggestions, email the author
Copyright 2015 Andrew Zimmerman