What Inventors Can Learn About Patent Claim Construction from the NCS v. Kobold Case
Understanding how patent claims are interpreted can make or break your intellectual property rights. A recent decision by the Federal Court of Appeal in NCS Multistage Inc. v. Kobold Corporation (2025 FCA 187) offers valuable lessons for inventors and businesses looking to protect their innovations through patents.
In this post, we’ll break down what this case teaches us about dependent and independent claims, how courts interpret them, and why getting your patent claims right is crucial to defending your invention.
What Was the Case About?
NCS Multistage Inc. and Kobold Corporation are competitors in the oilfield services industry. Both companies design and manufacture downhole tools used in hydraulic fracturing (fracking). NCS sued Kobold and its supplier, Promac Industries Ltd., for infringing five of its patents. In response, Kobold counterclaimed that NCS had infringed its own patent, Canadian Patent No. 3,027,571 (the “571 Patent”).
The Federal Court sided with Kobold, finding that NCS had infringed the 571 Patent and awarding Kobold a significant sum in legal costs. NCS appealed, arguing that the trial judge had misunderstood how to interpret the claims in the 571 Patent.
The Heart of the Dispute: What Do the Patent Claims Really Cover?
At the center of the appeal were four “Asserted Claims” in the 571 Patent: claims 6, 11, 12, and 16. These claims describe a shock-absorbing system for a sliding sleeve used in fracking tools. The key issue was whether these claims covered only one type of design (a “gap embodiment”) or both the gap and a “seal embodiment”.
The Federal Court had ruled that the claims only covered the gap embodiment. But NCS argued that this was a legal mistake because of how dependent and independent claims work in patent law.
Understanding Independent and Dependent Claims
To understand the court’s decision, let’s first clarify what independent and dependent claims are:
- Independent claims stand on their own. They define the broadest version of the invention.
- Dependent claims refer back to an earlier claim and add more specific features or limitations.
For example:
- Claim 1 (Independent): A tool with a sliding sleeve and a fluid chamber.
- Claim 12 (Dependent): The same tool, but with a specific type of barrier that moves with the sleeve.
- Claim 13 (Dependent on 12): Adds that the barrier includes a seal.
This structure means that Claim 12 must be broad enough to include both versions—with and without the seal—because Claim 13 narrows it down to just the sealed version.
What the Appeal Court Decided
The Federal Court of Appeal agreed with NCS. It found that the trial judge had misunderstood the legal relationship between dependent and independent claims.
Here’s what the Appeal Court clarified:
- Claim 12 includes both the gap and seal embodiments. Claim 13 simply narrows Claim 12 to only the seal version.
- Claim 16, when depending from Claim 12, also includes both embodiments.
- The trial judge wrongly excluded the seal embodiment from Claim 12, which led to further errors in deciding whether the 571 Patent was valid or infringed.
This mistake had a domino effect. Because the trial judge thought the Asserted Claims only covered the gap embodiment and concluded they were different from Kobold’s earlier patent (the 830 Patent), which covered the seal embodiment. That led the trial judge to reject NCS’s argument that the 571 Patent was invalid for double patenting—a rule that prevents inventors from getting multiple patents for the same invention.
The Appeal Court found that, properly interpreted, the Asserted Claims do overlap with the earlier patent and may not be patentably distinct. It sent the case back to the Federal Court to reconsider whether the 571 Patent is invalid for double patenting.
Key Takeaways for Inventors
This case offers several important lessons for anyone drafting or reviewing patent claims:
1. Dependent Claims Narrow, Not Broaden
A dependent claim adds limitations to the claim it refers to. It cannot expand the scope of the independent claim. If Claim 13 adds a seal, then Claim 12 must already include both sealed and unsealed versions; and so must claim 16 when depending from claim 12.
2. Claim Differentiation Is a Guide, Not a Rule
The principle of claim differentiation suggests that each claim should add something new. But it’s not a hard rule. Courts won’t assume that a dependent claim’s limitation is excluded from the independent claim unless there’s a clear reason to do so.
3. Get Claim Construction Right—It Affects Everything
How a court interprets your claims can determine whether your patent is valid, whether it’s been infringed, and whether you can enforce it. A mistake in claim construction can unravel your entire case.
4. Double Patenting Still Matters
Even though divisional patents (like the 571 Patent) now expire at the same time as their parent patents, double patenting is still a valid reason to invalidate a patent. If two patents claim the same invention or obvious variations, one may be struck down.
5. Be Clear and Precise in Your Claims
Ambiguity in your claims can lead to misinterpretation. Use clear language and ensure that each dependent claim logically narrows the scope of the claim it depends on.
Why This Matters to You
If you’re an inventor or business owner seeking patent protection, this case is a reminder that how you write your claims is just as important as what your invention does. A well-drafted patent can protect your innovation and give you a competitive edge. A poorly drafted one can leave you vulnerable to challenges and litigation.
Whether you’re filing your first patent or managing a portfolio of intellectual property, it’s essential to work with experienced patent agents who understand the nuances of claim construction and patent law.
Final Thoughts
The NCS v. Kobold decision underscores the importance of understanding the legal framework behind patent claims. It’s not just about having a great invention—it’s about protecting it properly.
If you’re considering filing a patent or want to ensure your existing patents are solid, now is the time to consult with a qualified patent agent. The right guidance can make all the difference in securing and defending your intellectual property.
Want to Read the Full Case?
You can access the NCS v. Kobold decision here.
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Updated October 2025
