By: Scott Denion   [8/31/22]

In the U.S., there are several bars to patentability. One such bar is referred to as the “public use” bar. Public use occurs when the invention is either (1) accessible to the public or (2) commercially exploited[1]. There is a short grace period in the U.S. (note that grace periods do not exist in many foreign countries) that permits public use of an invention before filing a patent application, but that grace period is only one year. After a year, that invention is no longer eligible for patenting. However, applying for a patent within the “grace period” after an offer for sale, public disclosure, or public use won’t count against you as prior art.

The public use bar can be applied broadly. Consequently, using your own invention before filing a patent application must be handled with great care. Below are some tips for identifying whether your use, if it falls outside or near the end of the one-year grace period, may be classified as “public use.”

Was Your Invention “Accessible to the Public” or “Commercially Exploited”?

To determine whether your invention was “accessible to the public,” we must first consider who is “the public.” While the “public” is not formally defined, a public use bar is created when the inventor shows the invention to, or allows it to be used by, another person who is “under no limitation, restriction, or obligation of confidentiality” to the inventor[2]. Thus, the “public” is generally anyone who is not under a limitation, restriction, or confidentiality obligation to the inventor. 

The main case addressing public use is Egbert v. Lippmann, 104 U.S. 333 (1881). The invention related to improved springs for corsets (it was an ancient case). For 11 years following the invention, the inventor’s intimate friend (and future wife) used the corset springs publicly but never actually showed them to anyone in public (nor would the springs have been visible had the corsets been seen). The court held there was public use even though the invention was hidden from view during use because no secrecy or restrictions on use were put into place[3]. From Egbert, it is clear that use by others must be handled with the utmost care, even if it is within the confines of your own business. Proper steps should be taken to ensure use is either restricted or others are obligated to keep details of the invention secret.

In a similar vein, Woodland Trust v. Flowertree Nursery Inc., 148 F.3d at 1370, 47 USPQ2d at 1366, addresses the matter of commercial exploitation. The court stated that an inventor’s prior commercial use beyond one year, while kept secret, may constitute a public use or sale, which would bar the inventor from obtaining a patent. If you are using your invention for commercial purposes, even if you aren’t sharing details of that use with anyone (i.e., you might consider it “secret use”), your use may still be found to be “public.” For example, suppose you own a nursery and you’ve developed a novel process of protecting your foliage plants from freezing. Use of that method, even if you aren’t showing it off to others, could constitute a public use. However, private use of your invention, where use is restricted to locations where there is a reasonable expectation of privacy (such as your dorm room or house), or for your enjoyment is not likely to rise to the level of the “public use” bar[4].

Was Your Invention “Ready for Patenting”?

Another factor to consider in the public use issue is when your invention was “ready for patenting.” Using the Pfaff test, this may be satisfied in two different ways: (1) proof of reduction to practice (which is bringing an invention to physical fruition) before the critical date (the critical date being one year before the filing date of the patent application for the present invention, which presumably has not yet happened if you’re reading this post) or (2) by proof that before the critical date the inventor had prepared drawings or other descriptions of the invention that were sufficiently specific to enable a person skilled in the art to practice the invention[5]. If your invention wasn’t fully formed or functional when you allegedly “publicly used” it, that supports your argument that a finding of “public use” would be inappropriate. This takes us to a final consideration.

Was Your Use Experimental in Nature?

A final consideration for the public use issue is whether the use was experimental, which occurs when there is a bona fide effort to perfect the invention to work for its intended purpose. As part of that, testing an invention in the normal context of its technological development is generally within the realm of permitted experimental activity[6]. One primary factor supporting experimentation is whether subsequent modifications or refinements of the invention occurred during the “experimentation” period. Further, when analyzing permitted experimental activity, the inventor must maintain sufficient control over the invention during testing, even when third parties use the invention.


Whether the “public use” bar has been invoked or not is fact-specific and depends on many factors. One must consider all the evidence (including, among other things, experimentation, the nature of the activity that occurred in public, public access to the use, confidentiality obligations imposed on members of the public who observed the use, and commercial exploitation) in making the determination. A licensed patent practitioner must consider the facts and advise you accordingly.  

To learn about how Dunlap Bennett & Ludwig can assist you with your legal needs, contact us by calling 800-747-9354 or by emailing

[1] American Seating Co. v. USSC Group, Inc., 514 F.3d 1262, 1267, 85 USPQ2d 1683, 1685 (Fed. Cir. 2008)

[2] American Seating Co. v. USSC Group, Inc., 514 F.3d 1262, 1267, 85 USPQ2d 1683, 1685 (Fed. Cir. 2008) and MPEP § 2152.02(c)

[3] See also In re Smith, 714 F.2d 1127, 1134, 218 USPQ 976, 983 (Fed. Cir. 1983)

[4] MPEP 2133.03(a)II.A.3.

[5] Pfaff v. Wells Elecs., Inc., 525 U.S. 55, 67, 199 S.Ct. at 311-12, 48 USPQ2d at 1647

[6] MPEP 2133.03(e)(6)I

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Posted in: Intellectual Property, Intellectual Property - Patents

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