In Kellogg v National Biscuit Co it was ruled that once a utility patent expires the patentee can never make a trademark-like claim to the exclusive use of the source-identifying function of the shape of products made using the patented machine.

What do they mean by the parts in bold?

1 Answer 1


Kellogg v National Biscuit Co is the foundation for the functionality doctrine. Essentially, this ruling means that product designs that are intrinsic to functionality cannot be protected under unfair competition or trademark laws.

The expiration of the patent term has no bearing on this--at no point can a trademark claim be made on these functional designs, even during the patent term, or if no patent exists or has been applied for. (However, if there is a valid patent covering the functional design, the patent owner can exclude others from using that design based on their patent rights.)

  • So as long as the functional design is not essential/indispensible to its functionality then it can be patented?
    – S J
    Dec 21, 2018 at 1:42
  • @SJ nope, the functionality doctrine applies to trademark protection, not patents. The purpose of utility patents is to protect functional aspects. Dec 21, 2018 at 16:09
  • So as long as the functional design is essential/indispensible to its functionality it cannot be trademarked?
    – S J
    Dec 21, 2018 at 17:35
  • Right. Trademark law does not prevent market competition. It says that you can't compete using someone else's trademark. Purely functional elements of a design can't be trademarked. Dec 21, 2018 at 17:39

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