In the 1894 U.S. Supreme Court case of Risdon Iron and Locomotive Works v. Medart, the court examined a dispute over patent rights for improvements in rolling mill machinery. The plaintiff, Risdon Iron and Locomotive Works, alleged that Medart had infringed on their patent by using an invention similar to theirs without permission or payment of royalties. However, the defendant argued that they were not infringing because their design was significantly different from what was described in the plaintiff's patent claim. The Supreme Court ruled in favor of Medart after finding substantial differences between his machine and those covered under Risdon's patents. They noted that while both machines performed similar functions (i.e., reducing metal into sheets), they achieved this through fundamentally different mechanisms - thus making them distinct inventions rather than variations on a single concept. This ruling reinforced principles around "non-obviousness" as a key criterion for determining whether something constitutes an infringement upon existing patents: even if two products serve identical purposes or produce identical results, they can still be considered separate inventions if there are significant differences in how these outcomes are achieved.

In the dissenting opinion for Risdon Iron and Locomotive Works v. Medart, Justice Brewer argued that the patent in question was indeed valid and should be upheld. He disagreed with the majority's view that it lacked novelty or inventiveness, asserting instead that there were significant differences between this invention and previous ones which justified its protection under patent law. Furthermore, he contended that even if some elements of an invention are not entirely new, they can still be patented if combined in a novel way to produce a unique result - something he believed had occurred here. Lastly, Justice Brewer criticized his colleagues for failing to give due weight to lower court findings supporting the validity of this patent.