Double Patenting in Canada: What Inventors Should Know from the NCS v. Kobold Case
Understanding Double Patenting and Divisional Patents
If you’re an inventor, entrepreneur, or business owner filing patents in Canada, you may have heard of double patenting. Double patenting is legal rule that prevents you from getting more than one patent for the same invention. This rule is especially important when filing divisional applications, which are patents split off from a parent application.
In NCS Multistage Inc. v. Kobold Corporation, the Federal Court of Appeal revisited how double patenting applies to voluntary divisional patents. The decision offers valuable insights for anyone trying to protect their inventions without risking invalidation.
In this post, we’ll explain:
- What double patenting is
- How divisional patents work
- What happened in the NCS v. Kobold case
- What this means for your patent strategy
What Is Double Patenting?
Double patenting prevents inventors from extending their patent rights unfairly by filing multiple patents for the same invention. There are two types:
- Same invention double patenting: When the second patent claims the exact same invention.
- Obviousness double patenting: When the second patent claims something that’s not significantly different from the first patent.
The goal is to stop “evergreening,” where companies try to keep control of an invention longer than allowed by law or where multiple patents for the same invention lead to multiple unnecessary enforcement issues.
What Is a Divisional Patent?
A divisional patent is a new patent application that comes from an earlier (parent) application. Inventors often file divisionals to separate different inventions or claim aspects that weren’t approved in the original application.
In Canada, divisional patents have the same filing date and expiry date as the parent patent. This change was made in 1989 to prevent evergreening. But even with the same expiry date, courts still apply double patenting rules to divisionals.
Case Summary: NCS Multistage Inc. v. Kobold Corporation
In this case, NCS Multistage Inc. appealed a Federal Court decision that found it had infringed Kobold’s Canadian Patent No. 3,027,571 (the 571 Patent). This patent was a voluntary divisional of Kobold’s earlier Canadian Patent No. 2,856,830 (the 830 Patent).
Both patents describe downhole tools used in hydraulic fracturing, specifically sliding sleeves with shock-absorbing features. NCS argued that the 571 Patent was invalid because it claimed the same invention as the 830 Patent—raising the issue of obviousness double patenting.
Key Legal Issue: Claim Construction
The heart of the case was how the Federal Court interpreted the Asserted Claims of the 571 Patent—specifically claims 6, 11, 12, and 16.
These claims describe two types of sleeve mechanisms:
- Gap embodiment: A sleeve with a space between it and the housing.
- Seal embodiment: A sleeve that seals against the housing.
The Federal Court ruled that the Asserted Claims only covered the gap embodiment, not the seal embodiment. This was important because the seal embodiment was already claimed subject matter in the 830 Patent.
But the Federal Court of Appeal disagreed finding these claims covered both the gap and sealed embodiments.
Appeal Court’s Findings: Broader Claim Scope
The Appeal Court found that the Federal Court made a legal error in interpreting the relationship between independent and dependent claims.
Here’s what the Appeal Court clarified:
- Claim 12, from which Claim 13 (the seal embodiment) depends, must include both the gap and seal embodiments.
- Therefore, Claim 16, which depends on Claim 12, also includes both embodiments.
This broader interpretation meant that the Asserted Claims of the 571 Patent overlapped significantly with the 830 Patent.
Double Patenting Still Applies to Voluntary Divisionals
Even though the 571 and 830 Patents expire on the same date, the Court confirmed that double patenting rules still apply. The key question is whether the second patent claims a patentably distinct invention.
The Appeal Court found that:
- Both patents shared the same inventive concept: a downhole tool with a dampening mechanism to control sleeve movement.
- The Asserted Claims of the 571 Patent, properly interpreted, appeared to claim the same invention as Claim 17 of the 830 Patent.
As a result, the Appeal Court sent the case back to the Federal Court to decide whether the 571 Patent is invalid due to obviousness double patenting.
Key Takeaways for Inventors
This case offers important lessons for inventors filing patents in Canada:
1. Double Patenting Still Applies to Divisionals
Even if your divisional patent expires at the same time as the parent, it can still be invalidated if it claims the same invention.
2. Claim Construction Matters
How your claims are written and how they relate to each other, can affect whether your patent is valid. Courts will look closely at the relationship between independent and dependent claims.
3. Be Careful with Voluntary Divisionals
If you file a divisional application voluntarily, make sure the claims are patentably distinct from the parent. Otherwise, you risk losing your patent.
4. Understand the Inventive Concept
When drafting claims, think about the core idea behind each one. If multiple patents share the same concept, you may face double patenting issues.
Final Thoughts
The NCS v. Kobold decision is a reminder that Canadian patent law still takes double patenting seriously, even for voluntary divisional applications. If you’re filing multiple patents for related inventions, make sure each one is clearly distinct in its claims and inventive concept.
This case also highlights the importance of precise claim drafting and understanding how courts interpret patent language.
If you’re considering filing a divisional patent, or defending one, you need to ensure your claims are clearly distinct from any earlier patents. Consulting with a qualified patent agent or lawyer can help you navigate these complexities and protect your invention effectively.
Want to Read the Full Case?
You can access the NCS v. Kobold decision here.
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Updated October 2025
