Tesla Split-Phase Patent Litigation (Feb. 17, 1906)

On January 19 Judge Kohlsaat rendered an opinion in a suit on final hearing involving the validity of the 1893 Tesla split-phase patents, the parties to the suit being the Westinghouse Electric & Manufacturing Company, complainant, and the Electric Appliance Company, defendant. The defenses in the suit were, first, that the claims at issue in the two 1893 patents are void for double patenting by reason of the grant to the same inventors of an earlier patent dated April 16, 1889; and second, that each of the patents in suit expired in the year 1903 by the reason of the expiration in that year of two British patents granted in 1889.

The court in its opinion stated that according to established judicial precedents, if the difference between the claims of the 1893 patents and those of the 1889 patent are only colorable, then either the former patents are void or the latter patent is void, but in fact, the later American patents were entirely unlike the earlier American patent, the latter being on means and the former a method.. Assuming that Tesla had taken out the 1893 patents in advance of the 1889 patent, he would in them have disclosed all the elements of the latter patent, but being the inventor in both cases he would have had a right to proceed in this particular manner. To hold the two 1893 patents in suit to be identical with the 1889 patent would be to do violence to the facts and the rule of law; the contention of double patenting does not apply since the earlier patent covers a method for operating a motor by the means disclosed in the later patents. This being so, the 1893 patents were also in no wise affected by the expiration of the English patents, since these were nothing more than improvements upon the 1893 patents. The finding of the court was for the complainants.