Legal Definitions - double patenting

Double patenting is a legal principle in patent law that prevents an inventor from obtaining more than one patent for the same invention, or for an invention that is merely an obvious variation of an invention they have already patented or applied to patent. The fundamental purpose is to prevent inventors from extending the period of patent protection beyond what is legally allowed, or from receiving multiple exclusive rights for essentially the same creative contribution.

There are two main types of double patenting:

• Same-Invention Double Patenting: This occurs when an inventor attempts to secure two separate patents that claim exactly the same invention. Patent law dictates that an inventor is only entitled to one patent for a single invention.
• Obviousness-Type Double Patenting: This arises when an inventor seeks a second patent for an invention that is not identical to one they already own (or have applied for), but is so similar that it would have been obvious to a skilled person in that field to derive the second invention from the first. This type of double patenting is often addressed by filing a "terminal disclaimer," which means the second patent's term is limited to expire at the same time as the first patent, preventing an unjustified extension of patent protection.

Here are some examples to illustrate how double patenting applies:

• Example 1 (Same-Invention Double Patenting): An inventor develops a novel type of solar panel that converts sunlight into electricity with unprecedented efficiency using a specific layered material structure. They successfully obtain a patent for this innovative solar panel design. A year later, the same inventor files a new patent application that describes the exact same layered material structure and efficiency claims, merely using slightly different wording in the patent application. This second application would be rejected for same-invention double patenting because it seeks to patent the identical invention already covered by their first patent, effectively trying to get two patents for one invention.

• Example 2 (Obviousness-Type Double Patenting): A company patents a unique software algorithm that significantly optimizes data compression for video streaming. Later, the same company develops a slightly modified version of the algorithm. This new version incorporates a common, well-known encryption standard to protect the compressed data, but the core data compression method remains the same and the encryption addition does not provide any unexpected or non-obvious functional improvements to the compression itself. If the company attempts to patent this modified algorithm, it could face an obviousness-type double patenting rejection. The addition of a standard encryption feature would be considered an obvious variation of the original patented compression algorithm, especially since it's by the same inventor. To overcome this, the company might file a terminal disclaimer, ensuring both patents expire concurrently.

• Example 3 (Obviousness-Type Double Patenting with a physical product): An engineer invents and patents a new type of ergonomic office chair featuring a unique lumbar support mechanism that adjusts automatically based on the user's posture. A few years later, the same engineer designs a second chair that incorporates the exact same patented lumbar support mechanism but changes the material of the armrests from plastic to a slightly more durable metal, without altering their shape or function in a non-obvious way. If the engineer tries to patent this second chair, it would likely be rejected due to obviousness-type double patenting. The change in armrest material is an obvious modification that does not introduce a new, non-obvious inventive step beyond the original patented chair, particularly regarding the core lumbar support innovation. A terminal disclaimer would be a common way to address such a rejection, linking the patent terms.