Expert Commentary

The Dangers of Delay in Filing Patent Applications

He who has rights, and sleeps upon them, justly loses them.Miller v. Bridgeport Brass Co., 104 U.S. 350 U.S. (1881)


Intellectual Property
November 2005

Typically, U.S. patent law gives a patent to the first person to conceive, build, and use an invention. Such an inventor, however, may forfeit his rights to a patent if he delays in patenting his invention. This article addresses the potential loss of patent rights due to unreasonable delay in patenting an invention.

Do the First To Conceive, Build, and Use An Invention Get To Patent It?

Not necessarily. Consider the following sequence of events.

  • January 1, 2000:
Charlie Craftsman, an ACME, Inc. employee, develops an idea for producing widgets. He discusses the invention with his coworker, Ivan Improver.
  • July 1, 2000:
Ivan Improver begins refining the invention into a more practical system that is cost effective.
  • January 15, 2001:
Ivan Improver presents the invention to the ACME board of directors. They debate the merits of the invention but fail to decide whether ACME should patent the invention.
  • February 1, 2001:
BACME, Inc., an ACME competitor, independently "invents" the same method for efficiently producing widgets.
  • November 1, 2001:
BACME files a patent application for its invention.
  • January 15, 2002:
After a market appears for the invention, ACME implements the new process and files a corresponding patent application. Who has the right to patent the invention—ACME or BACME?

Doesn't the First To Invent Get the Patent?

A U.S. patent is like a contract between the inventor and the U.S. government. If an inventor uses a patent application to tell the world how to make and use his invention, the government will give the inventor the right to prevent others from making or using the invention for 20 years. The belief is that the world will get new ideas by reading the application, which will result in more innovation and a more prosperous America. If the inventor delays in filing his application, however, the American people cannot read and use the patent application to think of other inventions.

To prevent this scenario, the government penalizes the inventor that delays too long in patenting his invention. Specifically, in the above scenario, the government may give the patent to BACME instead of ACME. How do they do it? The U.S. Patent and Trademark Office (PTO) uses an "interference" proceeding to determine whether ACME or BACME should prevail. The interference proceeding is like a miniature lawsuit—complete with attorney fees. In the above situation, BACME has the inside track on getting the patent as it filed its patent application first. However, even though it was the second party to file, ACME can be declared the true inventor provided it proves (1) it conceived the invention before BACME did, and (2) it did not abandon, suppress, or conceal the invention. 35 U.S.C. § 102(g).

How Can ACME Prove Its Date of Conception?

If the PTO begins an interference proceeding, ACME must first prove it conceived the idea before BACME filed its application. In patent terms, conception is the formation in the mind of a definite and permanent idea of the complete and operative invention. Mergenthaler v. Scudder, 11 App. D.C. 264 (D.C. Cir. 1897). ACME can clear this hurdle if it proves its inventor had a complete mental grasp of the invention before BACME's filing date. For this reason, it is well advised that every company have a system in place for inventors to document their ideas, preferably on a daily basis. Typically, lab notebooks and research progress reports are useful in proving conception. For example, ACME could use Charlie Craftsman's lab notebook to prove ACME's prior conception.

How Can ACME Abandon, Suppress, or Conceal an Invention?

The second thing ACME must show is that it did not abandon, suppress, or conceal the invention, which in determining priority, generally refers to two situations. First, an inventor actively "conceals" his invention when he withholds his invention from the public with the view of using the invention indefinitely and exclusively for his own profit. Eolas Techs. Inc. v. Microsoft Corp., 399 F.3d 1325 (Fed. Cir. 2005). Suppose ACME had decided to keep the new widget process as a secret (e.g., a trade secret) for several years and, only after its competitors entered the market, file a patent application. ACME may then be found to have actively concealed Charlie's invention from the public.

Alternatively, abandonment, suppression, or concealment may be inferred based on the inventor's unreasonable delay in making the invention publicly known. Id. In ACME's case, the time between conception and filing was over 2 years. Although ACME delayed in filing the patent application, in an interference, Charlie may be declared the true inventor if he can show the delay was "reasonable."

When Is A Delay "Reasonable"?

What is or is not "reasonable" is hard to predict. However, some guidelines do exist for knowing what kinds of delay are excusable. For example, a delay caused by the inventor improving or perfecting the invention is excusable, but a delay caused by working on refinements and improvements not reflected in the patent application, or commercializing the invention, are not excusable. Lutzker v. Plet, 843 F.2d 1364 (Fed. Cir. 1988). Importantly, an inventor is not expected to spend every waking minute on one invention and the mere passing of time may not be deemed "unreasonable" in light of the everyday limitations and problems encountered by the inventor. Time delays caused by ACME's management or legal counsel, however, are not as easily excused.

Is ACME Out of Luck?

Fortunately, even if abandonment is inferred, ACME may be able to "cure" this infirmity. This is because Charlie is not required to show diligence over the entire period between his conception and filing of the patent application; rather, he need only show that he did not abandon, suppress, or conceal the invention from a time just prior to BACME's filing until his own application was filed. So even if ACME abandoned its invention for a while, it may be able to obtain a patent if it proves it resumed development of the invention before BACME filed its application on November 1, 2001. However, if ACME was "spurred" into resumed activity upon learning of BACME's invention, there would be a strong inclination to grant priority to BACME. Apotex USA, Inc. v. Merck & Co., Inc., 254 F.3d 1031 (Fed. Cir. 2001).

So What Is the Take Home Message on Diligence?

PTO interferences lead to large attorney fees and unpredictable rulings. In short, do what you can to avoid them by being diligent. While you can't control who is the first to conceive an invention, you can increase your odds of obtaining a patent by maintaining diligence in inventive activity and expediently filing patent applications. Don't shoot yourself in the foot by delaying in applying for a patent, thereby opening the door for a later inventor to steal your invention.


Mark S. Solomon is an associate with Winstead Sechrest & Minick in Houston, Texas, where he specializes in intellectual property, including patent litigation, prosecution, and opinion work. He received his B.A. in chemistry from Northwestern University, his Ph.D. in organic chemistry from Emory University, and his J.D., summa cum laude, from South Texas College of Law. Before entering law school, he worked as a chemical expert for Bayer Polymers, where he received three U.S. Patents for chemical process technology. Dr. Solomon can be reached at


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