Legal Definitions - same-invention double patenting

Same-invention double patenting refers to a situation where an inventor attempts to obtain two separate patents for the exact same invention. Patent law is designed to grant a single period of exclusive rights for a single invention. Therefore, if an inventor already possesses a patent for a specific invention, or if another patent application is pending that claims the identical invention, any new application seeking to patent that exact same invention will be rejected.

This principle prevents an inventor from:

• Extending the period of their exclusive rights beyond what the law allows for a single invention.
• Obtaining multiple exclusive rights for the identical innovation, which would create unnecessary complexity and potential for abuse.

Here are some examples to illustrate this concept:

• Example 1: Identical Claims in Co-pending Applications

  Imagine a software engineer, Alice, invents a unique algorithm for optimizing data compression. She files a patent application (Application A) detailing this algorithm and claiming its specific method and structure. A few months later, due to an administrative oversight, her legal team files a second, entirely separate patent application (Application B) that contains claims describing the exact same data compression algorithm, with no new features or improvements. The patent office would reject Application B on the grounds of same-invention double patenting because it seeks to patent the identical invention already claimed in Application A, which is still pending.

• Example 2: Attempting to Re-patent an Already Patented Invention

  Consider a medical device company that successfully obtains a patent (Patent X) for a novel surgical tool with a specific articulating joint mechanism. Years later, an employee of the same company, perhaps unaware of Patent X, files a new patent application (Application Y) that describes and claims the exact same articulating joint mechanism for the surgical tool, without any modifications or enhancements. The patent office would reject Application Y because Patent X already grants exclusive rights to that identical invention. Granting a second patent for the same invention would improperly extend the monopoly period for that specific innovation.

• Example 3: Overlapping Claims in a Divisional Application

  A chemist, Dr. Chen, invents a new composite material that has both unique heat-resistant properties and exceptional flexibility. She files a patent application that describes both aspects. The patent examiner determines that the application actually describes two distinct inventions (the heat-resistant aspect and the flexible aspect) and requires Dr. Chen to pursue them in separate applications. Dr. Chen chooses to pursue the heat-resistant aspect in her original application and files a "divisional application" for the flexible aspect. However, if the claims in the divisional application, by mistake, also describe and claim the exact same heat-resistant composite material that is being pursued in the original application, rather than the flexible material, the divisional application would face a same-invention double patenting rejection. This is because it would be attempting to patent the identical invention already claimed in the parent application.