Tesla's Split Phase Motor Patent Decision

Judge Hazel, of the United States Circuit Court of the Western District of New York, has handed down an opinion sustaining the two Tesla fundamental patents (Nos. 511,559 and 511,569), covering the split-phase motor. The suit was instituted by the owners of the patents against the manufacturer of a wattmeter, and the court held that the wattmeter infringed the patents for the reason that it depended for its action on two currents differing in phase, derived from a single supply circuit.

The patents involved were the same that figured in the Catskill case, in which suit they were sustained by the Circuit Court, but declared invalid upon appeal. This reversal was on the grounds that the publication of a magazine article on April 22, 1888, by Prof. Galileo Ferraris fully described and disclosed the system covered by the patents. This publication was held to be prior to the date of the invention in suit and constituted an anticipation.

Judge Hazel, in his opinion, disagrees very materially with Judge Townsend, who wrote the opinion on appeal, declaring the patents invalid. The conflict arises from the different weight which the two judges gave to the testimony of the several leading witnesses, this testimony being held by Judge Townsend to be inconclusive, and by Judge Hazel to establish clearly that Tesla conceived the invention prior to the publication of the Ferraris article. Judge Hazel considers that, according to the testimony, Tesla conceived his split-phase invention in his laboratory at 89 Liberty Street, New York, and completed the same in the month of September, 1887; and that he made the disclosure thereof to others during the fall of 1887, especially to Mr. Brown and Mr. Nellis, and subsequently in the month of April prior to the Ferraris publication to his solicitor, Mr. Page.