Imagine That IP Law Blog

In most commercially significant inventions, strategic filing of various types of “child” patent applications (patent applications extending from an original or “parent” patent application) in various worldwide jurisdictions is useful in capturing the full value of an original invention. The types of child applications include continuation, continuation-in-part, and divisional applications. The following notable distinctions are worth considering before filing a child application in any jurisdiction.

The first distinction is between continuation and divisional applications. A continuation application is a follow-on application that pursues different claims flowing from the same, original disclosure. A divisional application pursues a distinct invention disclosed in the parent but not pursued there, often after a restriction or lack-of-unity objection. The US recognizes continuation, divisional, and continuation-in-part applications. Some other major jurisdictions around the world recognize only one of these types of applications.

The second distinction is between continuation and continuation-in-part (CIP) applications. A CIP is a unique type of application that is only available in the US. It can add new subject matter to a previously existing patent application, but claims relying on the new matter receive only the later CIP filing date and not the original priority date. In most jurisdictions outside the US, new subject matter generally requires filing a new application rather than a child application supported by an earlier priority. This makes the original specification of the parent application far more important in non-US jurisdictions.

The third distinction is between the right to file and the period during which that right exists. Each jurisdiction differs in the timing and requirements to file child application as shown in the table below –

The strategies for filing the child applications are often tied to the following consideration: the priority date and the appreciation of the best patent claims to pursue are almost never the same moment. A patent application has to be filed early to secure priority against later prior art. But the claims that ultimately matter, the ones that read on competitor products, on industry standards, on regulatory pathways, or on actual commercial implementations, may be discovered or best drafted later, with the benefit of information that was not available at the priority date.

The first strategy is maintaining pendency by keeping at least one patent application in a family active. A granted patent without a pending family member is largely fixed. That is, it cannot be reshaped to meet new commercial facts, such as commercial competitor products or patents, or industry standards. This strategy relies heavily on tracking and maintaining worldwide patent applications and ensuring they do not “issue out” if a continuation or divisional application is needed.

The second strategy relates to watching the marketplace and commercial activity. When a competitor releases a product, a pending continuation or divisional application can be amended or filed with claims that read on that product, provided the original parent disclosure supports the claim language. The main limitation for this strategy is the breadth of the original patent application. That is, a narrow or thinly described parent patent specification cannot support a precise claim in later child applications.

The third strategy considers patent validity and prior art. If a granted patent is challenged in litigation, opposition, or post-grant review, a pending family member can be used to pursue narrower claims that avoid the cited prior art while still covering the commercial embodiment. This works best when the pending case has been kept alive with an opportunity to amend rather than rushed to allowance.

The fourth strategy relies on using restriction requirements or unity of invention rejections. A restriction requirement in the US or a lack-of-unity objection elsewhere can create a clean path to filing divisional applications for non-elected inventions. In the US, restriction-triggered divisional applications may also receive a safe harbor against certain double-patenting attacks. In China, a unity objection is required to open the door to a later cascading divisional application that would not otherwise be available. The strategy can be used to file child applications by claiming multiple embodiments in the parent patent application to trigger such a rejection. In this strategy, it is important to keep track of all family members and their corresponding dates and claimed embodiments. This strategy is also limited to parent patent applications that extensively describe multiple inventions and their respective embodiments in sufficient detail to allow filing further applications.

The fifth strategy relates to filing patent applications to suit the underlying business model. Licensing businesses and/or patent holding companies tend to benefit most from aggressive continuation practice because the claims are exclusively the revenue-producing asset. Product companies often use continuations more selectively to protect market position, deter litigation, and preserve freedom to operate. Component suppliers may need fewer follow-on filings unless a specific downstream implementation becomes commercially important.

Standard-essential patents (SEPs) are a strong example of importance of the above strategies. Value of the SEPs depends on whether their claims map to the published standards. The standards are typically finalized after multi-year processes, and hence, claims drafted at the original priority date do not often match the finalized standards. The continuation or divisional applications are among the few reliable mechanisms for aligning the claim language of the SEPs to the finalized standards.

The controlling principle of these strategies is simple: keep commercially important patent families pending, draft the parent patent application broadly enough to support later precise claims, track the commercial marketplace and standards developments continuously, and make each filing before the relevant jurisdiction's window closes. In this manner, a patent owner can keep its options open and maintain flexibility.