When is it too late to file a patent?

In addition to the limitations on patentable subject matter, the patent laws of the United States also prohibit granting patents on otherwise patentable inventions due to certain occurrences, known as barring events. If a barring event has already transpired with respect to an invention, then there is no point in filing a patent application because no patent can ever issue that claims that invention. For example, if the invention was on sale or in public use anywhere in the world more than one year before an application is filed, the invention cannot be patented.

One act, no matter how small, trivial or obscure, can constitute public use and bar patentability. My favorite example of this situation involves a hundred-year-old story about a woman’s corset. A woman was complaining to her fiancé that her corset-stays were always breaking. Determined to make her some stays that would not break, he invented a pair with springs. He presented the stays to her and she wore them for more than two years before her fiancé applied for a patent. While they were worn in the corset underneath her clothing for a long time, no one else ever saw them. However, the court said that these acts placed the invention in public use, even though the public never learned of them and were highly unlikely to learn of them as a result of the woman’s use. Public use has nothing to do with the likelihood that the public will learn about the invention from the use. It has to do with whether the invention is used in public.

I had a client a few years ago that ran a teaser advertisement in a leading German newspaper in conjunction with an annual electronics tradeshow called Cebit. Although the new product was not publicly shown or sold at the tradeshow, the advertisement disclosed enough about the new product to render the invention unpatentable in the United States when the product was released a year and a half later.

It is important to note that deciding whether an occurrence constitutes a barring event can be tricky, as the statutory language has been heavily interpreted though numerous patent court cases. For instance, “on sale” means both “offered for sale” as well as “actually sold.” It is advisable to consult a patent attorney if the anniversary of a potentially barring event is quickly approaching, or if there are doubts as to whether an occurrence more than one year ago may already bar patentability.

Contact John Ferrell at if he can further assist you. 


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About the Author

John Ferrell is a founding partner of Carr & Ferrell LLP, one of Silicon Valley's foremost technology law firms, and specializes in patent and intellectual property law matters. He is the Chair of the firm's Intellectual Property Practice Group.