UNITED STATES SUPREME COURT DECISIONS ON-LINE

Letters patent No. 143,600, dated Oct. 14, 1873, and granted to John J. Vinton for an improvement in the manufacture of iron from blast-furnace slag, are void inasmuch as the process and appliances described in his specification and claim were known and in common use before the date of his alleged invention.

The bill of complaint alleged that Hamilton and the other defendants were infringing certain letters patent, No. 143,600, dated Oct. 14, 1873, and granted to John J. Vinton, one of the complainants, for an improvement in the manufacture of iron from furnace slag, and it prayed for an injunction to restrain them from further infringement, and for damages and an account of profits.

The answer denied that Vinton was the original or first inventor or discoverer of the patented improvement, and it denied infringement.

Upon final hearing, the bill was dismissed because the process described in the letters patent was known and in common use before Vinton's application for them, and the same were therefore null and void.

The complainants thereupon appealed the case to this Court.

The specification of the letters patent declares as follows:

"My invention relates to the production of cast-iron from the slag, or refuse of the smelting or blast furnace. Heretofore a large percentage of good metallic iron has been thrown away with the slag and become lost to commerce so far as its use as metallic iron is concerned. This is more particularly the case with rich ores, such at the Missouri and lake ores, which from their nature flux imperfectly in the ordinary smelting furnace. When imperfectly fluxed, the slag assumes a thick consistency, and cools with a general grayish color, and though the presence of metal in it cannot be detected by the eye, yet the slag will be found to be of comparatively great specific gravity, and in fact contains a very large percentage of good metallic iron, often as great as the amount of metal reduced from the ore in the process of smelting. "

Page 104 U. S. 486

"To reduce this metal from the heavy slag of the smelting furnace, and thereby increase the production of iron from the same amount of ore, is the object of my invention. To accomplish the desired result, I employ a cupola furnace, but furnaces specially adapted to the purpose may be constructed and conveniently used in connection with the blast furnaces where the iron is smelted."

"The heavy slag is first pulverized or broken up into small pieces, or it may be made granulous or spongy by passing water or air through it when in a molten state or in any of the well known ways. A bed of coke or other suitable material is first placed in the cupola, and on the top of the coke a small quantity of scrap or other oxidized iron (preferable scale or black oxide of iron) is sprinkled."

"The slag to be operated on is then introduced as evenly as possible on the top of the coke and iron oxide, and on the top of the slag I sprinkle a small quantity of limestone broken up into small pieces, then a layer of coke, followed with scrap and scale slag and lime as before alternately until the whole cupola is charged."

"The fuel is then ignited, and when the fire is above the tuyeres, the blast is turned on to the full. Owing to the presence of the iron oxides, the heat is very great when brought in contact with the slag, and the latter is speedily reduced, and as the operation goes on, fresh charges of the materials are supplied from the top of the cupola, provision being made for the passage of the remaining slag from the furnace at a point below the tuyeres."

"In this way, it will be seen that the process is continuous, and the furnace is not permitted to get cool."

"The charge is made up in about the following proportions, but may be slightly varied as occasion requires: after the furnace is in operation, first, three bushels of coke; second, fifty pounds iron oxide (scrap or scale); third, eight hundred pounds slag; fourth, one-fourth of a bushel of limestone, thrown into the cupola in succession, and from time to time as required."

"When there is much sulphur in the iron, a small quantity of the black oxide of manganese may be blown in through the tuyeres, and salt or litharge, or a mixture of any two or all three of these ingredients, may be used in this manner with good effect. The iron thus obtained is run into moulds in the usual way."

"What I claim as my invention and desire to secure by letters patent is the herein-described method of reducing iron from the slag or refuse of blast or smelting furnaces, substantially as set forth. "

Page 104 U. S. 487