The right to sue for patent infringement does not begin until a patent issues. However, provisional protection begins upon publication of the application eighteen months after the earliest priority date. One who infringes a claim in a published patent application may be liable for a reasonable royalty, provided that the applicant gives the infringer “actual notice of the published patent application”.[1] However, this provisional right is contingent upon a patent issuing, so there is no liability if no patent issues, and no cause of action until the patent issues.
While a patent application is pending, the applicant can and should mark the invention “patent pending.” Marking the invention “patent pending” does not give the applicant any additional legal rights (because patent protection does not begin until a patent issues), but marking has an important practical effect of deterring competitors. Because patent applications are maintained secret, competitors cannot find out what the application covers or even when or if a patent will issue. Thus, a competitor who copies a product marked “patent pending” is taking a chance because a patent could issue at any time covering the copy, which could be used to stop further use or sale of the copies. For many businesses, the publicity value of “patent pending” together with this deterrent effect justifies the cost of filing a patent application. Only products that are actually the subject of a pending application can be marked “patent pending.” The patent laws prohibit falsely marking an invention “patent pending” or “patented,” and impose fines for violations of these prohibitions. Moreover, false patent marking may be grounds for an action for unfair competition by those injured by the false marking.[2]
[1] 35 U.S.C. §154.
[2] 35 U.S.C. §292 “Whoever marks upon, or affixes to, or uses in advertising in connection with any article, the words ”patent applied for,” ”patent pending,” or any word importing that an application for patent has been made, when no application for patent has been made, or if made, is not pending, for the purpose of deceiving the public – Shall be fined not more than $500 for every such offense.”