Legal Definitions - statutory double patenting

Statutory double patenting is a legal principle in patent law that prevents an inventor from obtaining more than one patent for the *exact same invention*. It is rooted in the idea that a single invention should only receive a single patent grant, ensuring that the public domain is not unduly restricted and that patent rights are not unfairly extended beyond their intended term. This type of double patenting arises when the claims in a later patent application or granted patent are identical in scope and subject matter to claims in an earlier patent or application by the same inventor.

Here are some examples to illustrate this concept:

• Example 1: Identical Claims in Separate Applications

  An inventor, Dr. Anya Sharma, develops a novel method for purifying water using a specific filtration membrane. She files a patent application (Application A) detailing this method. A few months later, perhaps due to an administrative oversight or a misunderstanding of the rules, she files a second, entirely separate patent application (Application B) that contains claims describing the *exact same water purification method* with identical scope and features as those in Application A. A patent examiner reviewing Application B would likely reject it on the grounds of statutory double patenting, as Dr. Sharma is attempting to secure two patents for the identical invention.

• Example 2: Overlapping Claims in a Parent and Divisional Application

  A company, "Tech Innovations Inc.," invents a new type of secure data encryption algorithm. They file a comprehensive patent application (the "parent application") covering various aspects of this algorithm. During the examination process, the patent office might require them to divide the application into multiple parts if it claims more than one distinct invention. Tech Innovations Inc. files a "divisional application" to cover a specific sub-feature of the algorithm. However, due to an error, some of the claims in this divisional application are drafted in a way that makes them *identical* in scope and subject matter to claims already allowed or granted in the parent application. The patent office would reject these identical claims in the divisional application based on statutory double patenting, preventing the company from obtaining two patents for the very same encryption method.

• Example 3: Attempting to Re-patent an Expired Invention

  Mr. Ben Carter invented a unique mechanical device for opening child-proof containers, and his patent for this device was granted and subsequently expired after its 20-year term. Years later, Mr. Carter attempts to file a new patent application for the *exact same mechanical device*, using claims that are identical to those from his original, now-expired patent. The patent office would reject this new application due to statutory double patenting. The purpose of patent law is to grant a limited monopoly for a specific period; allowing a new patent for an identical, previously patented invention would unfairly extend that monopoly and prevent the public from freely using an invention that should have entered the public domain.