Tesla Synchronous Motor Patents Upheld

In pursuance of a decision handed down by him on February 20th, in the United States Circuit Court for the Eastern District of Wisconsin, sustaining the contention of the Westinghouse Electric and Manufacturing Company that synchronous motors made by the National Electric Company were an infringement of the broad rights covered in Tesla patents Nos. 381,969 and 382,281, Judge Seaman, in Milwaukee, on February 24th, enjoined the National company from the sale of such motors. The decision in the suit is the first that has been obtained in the litigation begun some time ago by the Westinghouse company to prevent the sale of synchronous motors and rotary converters by American manufacturers not enjoying a license under the Tesla polyphase-motor patents. The hearing in the suit against the National Electric Company was conducted before Judge Seaman on February 6th and 7th, Thomas B. Kerr and Parker W. Page appearing for the Westinghouse company.

The Tesla patents involved in suit have been the subject of considerable litigation in the last few years. Other manufacturers have been enjoined from manufacturing induction motors, but the decision in the suit against the National company is the first court ruling that the synchronous motor is within the generic Tesla invention. Extracts from Judge Seaman’s decision are as follows:

“The defendant’s contentions are, in substance, that the Tesla invention, embodied in each of the patents, is the rotating-field mode of operation, which is ‘the production of the conjoint effect of out-of-phase currents of a progressive shifting by the polarity,’ and thus ‘identical in its effect with that of a rotating physical magnet’ that it is limited to a self-starting motor so operated, and both by the terms of the patents and the state of the art, the defendant’s synchronous motor with direct-current excitation is not within the invention; that the defendant’s synchronous motor is simply a reversed ‘two-phase alternating-current dynamo of the prior art used as a generator,’ adapted to alternative use; and that the claims of patents 381,969 and 382,281, which bring in ‘direct-current excitation producing synchronous operation,’ must be limited to such use ‘after the motor is started by the Tesla means and method and brought up to speed.’ If the invention is so limited by the prior art it is plain that the defendant escapes infringement. On the other hand, if not so restricted, it is equally clear that the claims of the patents are broad enough to reach the defendant’s means and method of operation.”

“The Tesla discovery for which these patents were granted revolutionized the art of electrical power transmission, as well demonstrated in the record from both judicial and scientific standpoints. Judge Townsend’s definition, in reference to the generic patents in the New England Granite case, repeatedly approved by other courts, is adopted for this consideration, namely, ‘Tesla’s invention, considered in its essence, was the production of a continually rotating or whirling field of magnetic forces for power purposes by generating two or more displaced or different phases of the alternating current, transmitting such phases, with their independence preserved, to the motor, and utilizing the displaced phases as such in the motor.’ So viewed, the patent monopoly was rightly granted for its brief term to the use of the means and methods thus discovered. While it could not exclude the known uses of the prior art, it is surely entitled to be protected against like motor structure and mode of operation, not clearly disclosed in the prior art, and the patent claims to that end must be fairly construed in conformity with the rule applicable to such inventions. I am of the opinion, therefore, that the several contentions for the defendant are either without force or untenable.”

“Whether the effect of the Tesla invention in its production of the ‘whirling field of magnetic force’ is identical with that of a rotating physical magnet, as argued by experts and counsel, does not impress me as material to this issue. Nor does it seem material that in the one form of motor ‘the rotation is produced by the unaided effect of alternating out-of-phase currents,’ as described by counsel, and that so applied a self-starting motor is obtained. The discovery was of means and method in the polyphase rotating-field motor to produce the whirling field of force, and employment thereof was patentable with or without direct-current excitation of the armature or secondary element. So the fact that its use produced a self-starting motor without the aid of such excitation cannot alone serve to limit the invention to that effect, and I find no such limitation in the terms of the patent. The quotations from the arguments of counsel and experts for the complainant in prior cases, urging the distinction of this self-starting effect in reference to the application of the generic patents to non-synchronous motors, are without force in the present controversy, and it is unnecessary to ascertain their consistency or inconsistency with the interpretation sought on this hearing. Unless limitation to self-starting motors arises out of the prior art none can be imposed upon the claims in suit.”

“The further propositions urged by way of defense — aside from the defense founded upon prior inventions of the synchronous type to be considered — are these — (1) that the synchronous motor of the defendant is the old generator of the art, simply reversed, and (2) that the Tesla invention is not present therein, because (as asserted) ‘the prepon-rating magnetization of the direct current displaced and obliterates the ‘shifting alternating-current magnetization,’ or Tesla’s ‘whirling field of force.’ However specious both propositions appear on their face and in the argument, neither of them impresses me as controlling.”

“I believe that no proposition in the able and extended arguments on the part of the defense have been overlooked in my consideration of this case, although it has not seemed needful to discuss all of them for the purposes of this opinion. My conclusions are that the defendant’s synchronous-motor structure and operation are within the generic invention as patented, and expressly covered by the claims of Nos. 381,969 and 382,281; that the invention is utilized in the defendant’s motor operation, notwithstanding the introduction of direct-current excitation to make it synchronous, in lieu of the full realization of the revolving-field effect for self-starting; that such supplemental aid does not escape infringement, with or without advantage in such associations; and that, in any view, the combination patents referred to are not limited to after-effect of the direct-current excitation, but apply to the defendant’s combination. Decree will be entered accordingly as prayed in the bill.”

The National Electric Company has given notice of appeal from the injunction. On its behalf, it is also declared that the patents expire in May of this year in any event.