Minerals Separation, Ltd. v. Hyde

Background

A patent owner and its general licensee sued a defendant for using a method to concentrate ore without permission. The patented method, developed by experienced London metallurgists, uses a minute amount of oil — a fraction of one percent on the ore — plus strong agitation to beat air into the mixture. That action produces a stable froth of air bubbles with only trace oil that carries 70–80% of the mineral particles to the surface. Earlier methods used much larger oil quantities or relied on oil buoyancy. The District Court had sustained many claims and found infringement, but the appeals court reversed and ordered dismissal, leading to this Supreme Court review.

Reasoning

The central question was whether this low‑oil, agitation froth process was a new invention over prior patents and experiments. The Court found the key advance was using critical, vanishingly small oil proportions and vigorous agitation so air bubbles, not oil bulk, lift minerals. The Court relied on extensive experimental records, expert testimony, and evidence the method had rapidly come into widespread use. The patentees ran extensive tests using high‑speed Gabbett mixers and tabulated results showing a durable froth carrying most of the minerals. The Court held claims 1, 2, 3, 5, 6, 7 and 12 valid and infringed, but found claims 9, 10 and 11 invalid as too broad.

Real world impact

The ruling lets the patent owner enforce protection for the specific low‑oil froth technique, allowing stops against competitors using that method, while narrowing the patent to prevent overbroad claims. The opinion noted the process had already been adopted worldwide and emphasized that the patent is confined to the "critical proportions" described. Claims 4, 8, and 13 were not decided here.