Neilson v Harford

For an ordinary smith’s fire or forge, an air-vessel or receptacle capable of containing 1200 cubic inches will be of proper dimensions; and for a cupola of the usual size for cast-iron founders, an air-vessel capable of containing 10,000 cubic inches will be of a proper size.It was asserted that using the hot blast produced three times as much iron with the same amount of fuel as the cold blast did.

[6] In addition, the hot blast process permitted the use of cheaper coal instead of more expensive coke, which made it economical to exploit cheaper low-grade iron ore.[7] The Exchequer Court rejected the argument made by the defendants that the patent merely covered the principle that furnace temperature could be increased by injecting hot air instead of cold air into the furnace, for the principle of itself could not be patented.

Baron Parke observed, We think the case must be considered as if, the principle being well known, the plaintiff had first invented a mode of applying it by a mechanical apparatus to furnaces; and his invention then consists in this — by interposing a receptacle for heated air between the blowing apparatus and the furnace.

Some accused infringers used a network of pipes, which they claimed worked better than Neilson’s box-like receptacle, because of a greater surface area, which facilitated better heat transfer.

[15] Thus, if the implementation is concededly conventional, as it was in Flook, or trivial, as it was in Funk Brothers Seed Co. v. Kalo Inoculant Co.,[16] the subject matter cannot be patented.

This analysis was repeated in Mayo Collaborative Services v. Prometheus Laboratories, Inc. [17] In the Neilson opinion, however, there is no mention of whether the expedient of interposing a heated box in the air line involved an inventive step.