by Dennis Crouch In the patent context, functional limitations describe inventions in terms of their function or intended use, rather than their specific structure or components.Such claims have been subject to much debate and litigation throughout the history of the US patent system.Notable Supreme Court cases like O'Reilly v. Morse, 56 U.S. (15 How.) 62 (1854) and Halliburton Oil Well Cementing Co. v. Walker, 329 U.S. 1 (1946) significantly impacted patent practice and the balance between functional and structural claim drafting.