Discerning the Purpose and Means of Williamson v. Citrix

Discerning the Purpose and Means of Williamson v. Citrix

by Dennis Crouch

Functional claim language has long been a mainstay of U.S. patent law. In the historic case of O’Reilly v. Morse, 56 U.S. 62 (1853), the famous inventor of the single-line telegraph (Morse) claimed patent rights to the use of electro-magnetism for transmitting a signal–without limit to any “specific machinery or parts.” Id. The Supreme Court found the claim “too broad and covers too much ground.” Although Morse’s claim directed to a single functionally described element was deemed improper, patent attorneys quickly learned that a combination of functionally-claimed elements could work. An example of this is famously seen in the Wright Brothers early aircraft patents. See US821393.

The Supreme Court pushed-back again on functional claims–perhaps most notably in Halliburton Oil Well Cementing Co. v. Walker, 329 U.S. 1 (1946).  In Halliburton, the Supreme Court invalidated Walker’s means-plus-function claims as indefinite after holding that it was improper to claim an invention’s “most crucial element … in terms of what it will do rather than in terms of its own physical characteristics or its arrangement in the new combination apparatus.”  Id.

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