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

<p>What do they mean by the parts in bold?</p>

<p><em>Kellogg v National Biscuit Co</em> is the foundation for the <a href="https://en.wikipedia.org/wiki/Functionality_doctrine" rel="nofollow noreferrer">functionality doctrine</a>. Essentially, this ruling means that product designs that are intrinsic to functionality cannot be protected under unfair competition or trademark laws.</p>

<p>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.)</p>

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