Tesla Split-Phase Patent Sustained

Judge Archbold, of the United States Circuit Court for the Eastern District of Pennsylvania, has handed down a decision in a case involving the Gutmann wattmeter, which sustains the fundamental Tesla split-phase patent. The principal defense was a publication by Ferraris in 1888 on the rotary field and of the means for obtaining polyphase from single-phase currents. These disclosures were made in a paper read by Prof. Ferraris before the Royal Academy of Sciences of Turin, Italy, in March, 1888, a portion of which was published on April 22 following, in L’Elettricita. The Tesla patents in suit were not applied for until December 8 following, but the court held that the testimony in the case showed conclusively that Tesla had, early in May, 1888, a complete grasp of the split-phase idea; and not only is the invention beyond question carried back by it to that period, but the patent not being able to be worked out in a day, ground is thus laid for an earlier date if there is fair evidence to warrant it. The court holds there is such evidence, testimony showing that Tesla disclosed the principles of his invention at a date prior to April 22 to his patent solicitor, the date being somewhere between the 8th and the 18th of April. This evidence is supported also by the testimony of a former business associate of Mr. Tesla, who states that Tesla spoke to him of the idea in the summer or fall of 1887. The date claimed by Tesla of his discovery was September, 1887.

After reviewing at great length the testimony as to priority between Ferraris and Tesla, and deciding in favor of the latter, the court considered at equal length the question of infringement of the Tesla split-phase patent by the Gutmann meter. Its conclusion is that the construction of the meter is in effect a motor in which the armature is operated upon by two independent interconnecting circuits produced by passing through them a divided and dephased alternating current derived from a single source, this apparently realizing the patents in suit. After further consideration of the principles of the meter in suit, the court decided that the meter infringed the Tesla patent. The finding is that the patents in suit are valid and have been infringed.

An interesting portion of Judge Archbold’s opinion is that in which he gives a history to date of the opinions rendered in suits involving the Tesla split-phase patents. Judge Townsend, in reviewing the fundamental patents, discussed the alleged disclosures of Siemens, 1878; Bailey, 1879; Deprez, 1889, 1884, and Bradley, 1887, and the claims advanced for them as anticipations, which he held to be unfounded, and these conclusions were affirmed on appeal. The essence of the invention was declared by Judge Townsend to be “the production of a continuously-rotating or whirling field of magnetic forces for power purposes by generating two or more displaced or differing phases of the alternating current, transmitting such phases with their independence preserved to the motor, and utilizing the displaced phases as such therein.”

The same patents came up before Justice Brown and a similar result was reached. The Dumesnil (1884) and the Cabanellas (1885), two French patents, which had not been brought forward before, were particularly relied on as anticipations, but were distinguished from those in suit in a carefully-expressed and convincing opinion. These French patents, however, according to Judge Brown, established that Tesla was not the first to employ alternating currents out of phase with each other for power purposes, so that the expressions in previous cases which attributed this to him would have, as he thought, to be qualified if not recalled. But it was at the same time pointed out that in neither the Dumesnil nor the Cabanellas was there a resultant magnetic force, the distinctive feature of the Tesla invention; each of the others named providing for the independent action of separate alternating currents operating on different ends of the motor armature without any play of the magnetic and electric forces in between. “As it stands, the Cabanellas patent is unintelligible to me, but taking it as it is explained by the defendant’s experts and illustrated by the exhibit in evidence (of the correctness of which, however, I have much doubt), there is nothing more at the best than a mechanical combination of the two operative devices like the opposite cranks on the same axis of a locomotive driving wheel. There is no conjoint operation as in a Tesla motor of the two energizing circuits by means of a combined magnetic influence to produce a common result. It is important, however, to observe that while in no sense anticipations, the Dumesnil and Cabanellas serve to limit the invention of Tesla — if not, indeed, so limited in his patents themselves — to a device in which a magnetic resultant of dephased alternating currents exist, the mere use of alternating currents out of phase with each other made otherwise effective being something aside and different.”

The derivative patents in suit were first considered in the Dayton Fan & Motor case and affirmed, and a decision rendered in substantial accord with those which had preceded it. One defense there, as in the present suit, attempted to be made, was that it involved no inventive skill when once the practicable use of alternating currents of different phase was established, to substitute the dephased split current which was a well recognized equivalent; but it was not so held, nor could it be in the present case. This question was practically put at rest in this court by the decision of Judge McPherson in a case where two of the earliest Tesla split-phase patents were sustained. But aside from that, and upon an entirely independent consideration of it, Judge Archbold says the same conclusion must be reached.

The patents in suit were also before Judge Lacombe, and in addition to the attack made upon them in other cases, it was further urged that, in the paper read by Prof. Ferraris before the Royal Academy of Sciences, of Turin, Italy, March 18, 1888, a portion of which was published on April 22 following, at Milan, in L’Elettricita, a journal devoted to electrical subjects, not only was there a full disclosure of the transmission of electric power by means of alternating currents of different phase, but also the use for the same purpose of a dephased split current derived from a single source, the same as in the patents in suit. Upon a due consideration of the opposing proofs, the invention of Tesla was held to be carried back of this publication; but on appeal the decision was reversed, the evidence brought forward by the complainants not being considered sufficient for that purpose; a conclusion which was followed by Judge Colt in a case by the same plaintiffs against the Stanley Instrument Company, in the First Circuit, not yet in print. This, said Judge Archbold, in concluding his review, and the matter of infringement, are the overshadowing questions in the present case.

Discussing the contention that a meter is not a motor, and that on this ground of itself no infringement can be charged, Judge Archbold said that, as pointed out by Judge Lacombe in the Catskill case, while the Tesla patents contemplate the production of power, they are silent as to the amount of it; and as a meter armature rotates against the action of a permanent magnet and turns a spindle which operates the registering devices, the production of some power is necessarily involved. It is somewhat aside from the question, but still it is a circumstance that Gutmann himself, in accordance with whose patents the meters in question are constructed, recognizes and claims therein that this device may be used for power purposes also. No doubt the strict object of a meter of this class is to measure and record the element which passes through or actuates it, gas, water, the electric current, or whatever it may be; but where, as here, it is, in mechanical construction, nothing more than an adapted motor with meter attachments, it cannot escape infringement on the plea. Judge Archbold holds that there is nothing in conflict with this, when rightly considered, in what is said in an opinion cited relating to a water meter. The attempt there made was to defeat a special safety appliance of a water meter by references drawn from the general motor art, and it was in that connection that it was held that the two were not the same.