The Polyphase Patent Situation

Last week we referred to a list of patents issued by the owners of the recently expired Tesla fundamental rotary field patents. A notice accompanying the list stated that certain manufacturers are offering to supply polyphase induction and synchronous motors and apparatus for use therewith because certain of the Tesla patents have expired, and intending purchasers of polyphase apparatus are notified that numerous other patents relating to these subjects are still in force. Below is given an analysis of the various patents named in the list, together with a brief account of the litigation in which some of the patents have figured. In addition to the patents in the list above referred to are several others which in a minor way have also figured in this same litigation.

TESLA PATENTS.

Of the Tesla patents the most important are the two fundamental patents on the split-phase system. These are Nos. 511,559 and 511,560, issued December 26, 1893, on applications filed December 8, 1888. Both of these patents have been in litigation for some years.

Judge Thompson, of the Southern District of Ohio, filed an opinion February 6, 1901, sustaining the patents in a suit brought against the Dayton Fan & Motor Company. The courts held that the first-mentioned patent covered the case of an alternating current passing through one energizing circuit and inducing a second current in the other energizing circuit; and also the case of two motor energizing circuits connected in derivation or multiple arc with the main circuit from the source. The second patent was held to cover apparatus for carrying out the method by derivation. It was also held that the retardation of phase by artificial means and its conversion from an element of disadvantage to one of usefulness in the transmission of electric power, must be regarded as evidence of invention. The court also pronounced against the defense that the inventions of the two patents in suit are covered by a prior patent issued to the same inventor, No. 416,193, issued December 3, 1889, on an application filed May 30, 1889. The claims of this patent are for an alternating-current motor having two or more energizing circuits, the coils of one circuit being composed of conductors of large size or low resistance and those of the other of fewer turns of wire of smaller size or higher resistance; also the combination with long and short field cores of energizing coils, including in independent circuits, the coils on the longer cores containing an excess of copper or conductor over that in the others; also, a field magnet composed of magnetic plates having an open center, and pole pieces or cores of different length, coils surrounding the cores and included in independent circuits, the coils on the longer cores containing an excess of copper, the longer cores being set in recesses in the iron core formed by the plates. It was held that in this latter patent there is claimed only a specific form of construction and not the method or process by which all motors of its class are operated. This decision was sustained on appeal in an opinion filed November 5, 1902. Judge Severen, who wrote the opinion, defined patent No. 511,559 as relating to a method or methods of transmitting alternating currents proceeding from one original source to both of the energizing circuits of a motor, and at the same time retarding the phases of the current in one circuit to a greater or less extent than in the other. The second patent was defined as relating to means employed in the transmission of electrical power to a motor through divided currents derived from a single current proceeding from the generator; the said divided currents being so regulated with reference to each other as to arrive at their destination in the motor-alternator.

In an opinion filed August 22, 1901, in a case in which the Catskill Illuminating & Power Company was defendant, and in which the Sheeffer meter figured as the alleged infringing device, Judge Lacombe held that two claims of the first patent were infringed and the first claim of the second patent. The second claim of the latter patent was stated to be restricted to apparatus in which the energizing currents are connected in derivation of multiple arc with the supply circuit, and this claim was declared not to be infringed. The Catskill suit was appealed and in an opinion written by Judge Townsend and filed February 25, 1903, the court below was reversed. It was held that the two patents were invalid on the ground that the system covered by the patents in suit was fully described in an article by Prof. Ferraris printed in an Italian journal April 22, 1888, which date was prior to the invention by Tesla.

The same two patents figured in litigation in the Massachusetts Circuit Court. On March 11, 1903, Judge Colt dismissed a bill alleging infringement of the patents by the Stanley Instrument Company on the ground that it had been shown by Judge Townsend that the Tesla patents were anticipated by the Ferraris publication. Upon appeal, in an opinion written by Judge Putnam, filed September 9, 1904, Judge Colt's decision was reversed, it being held that the testimony of a witness, Mr. Page, had established that Tesla had conceived the invention prior to the date of the Ferraris publication. Owing to the conflict in the two decisions on appeal, the case came before the United States Supreme Court on petition for a writ of certiorari. This was denied on the grounds that the two courts had before them substantially different records and therefore there was no conflict. The two patents were sustained in the United States Circuit Court for the Eastern District of Pennsylvania in a suit involving the Guttmann wattmeter. The opinion was rendered by Judge Archbald, who dismissed the defenses based upon patents issued to Dumesnil and Cabanellas and on the Ferraris publication, declaring the two patents to be valid. In another case before the United States Circuit Court for the Western District of New York, decided February 9, 1904, involving also the Guttmann meter, Judge Hazel held the two above patents to be valid, the defense being the Ferraris publication.

In still another case involving the Sheefer meter, Judge Kohlsaat, in an opinion filed March 26, 1904, sustained the patents, basing his decision upon previous decisions in their favor. Judge Buffington, in the United States Circuit Court for the Western District of Pennsylvania, on March 28, also sustained the patents in a case involving the Sheefer meter, basing his decision upon prior decisions sustaining the patents.

No. 416,194. — Electric motor, December 3, 1889. Application filed May 20, 1889. An induction motor with field and armature of equal strength when energized by a given current; the combination with field and armature coils of equal mass, of energizing coils containing equal amounts of copper. The specification states that such a motor will give the maximum output for the material used.

No. 445,207. — Electromagnetic motor, January 27, 1891. Application filed May 20, 1889. The motor is of the split-phase induction type, and is a self-starting, single-phase machine. There are on the motor two energizing circuits, one of which is connected directly to the source of supply of current, while the second circuit is placed in inductive relation to the first, the two circuits being constructed with different time constants. In the operation of this motor the current impulses in the first, or primary, coils produce currents in the secondary coils, and by the conjoint action of the two an unsymmetrical revolving field is obtained. There are three claims. In the Scott and Janney case it was held that this patent did not conflict with the patents there in suit, as it carried a distinct invention.

No. 459,772. — Electromagnetic motor, September 22, 1891. Application filed April 6, 1889. The seven claims relate to the combination of an induction motor used as a starting device for a synchronous motor. The induction motor is mounted on the same shaft with the synchronous motor, the number of poles of each being so chosen as to give to the former motor a speed greater than that of the latter. The use of a self-starting, split-phase induction motor is disclosed in the drawings, but not referred to specifically in the claims.

No. 487,796. — System of electrical transmission of power, December 13, 1892. Application filed May 15, 1888. The four claims cover a multipolar generator with independent armature circuits used in combination with a motor having independent energizing circuits, the type of neither the generator nor the motor being specified. The drawings show two-phase generators and motors, all of which are of the synchronous type. The claims dwell upon the use of a number of motor poles greater or less than the number of generator armature circuits.

No. 511,915. — Electrical transmission of power, January 2, 1894. Application filed May 15, 1888. No. 555,190. — Alternating motor, February 25, 1896. Application filed May 15, 1888. These two patents figured as a single issue in a suit against the Scott & Janney Co., decided September 27, 1899, in the United States Circuit Court of the Eastern District of Pennsylvania. Judge McPherson, in his opinion, held that the invention of the patents was for a specific method of obtaining difference of phase, namely, by induction instead of self-induction, and therefore they did not conflict with the fundamental rotary field and the fundamental split-phase patents. The motor has two independent energizing circuits through only one of which current from the source is passed. In the second circuit the current is produced by the inductive effect of the current in the first circuit.

STANLEY PATENTS.

No. 469,809. — System of Electrical Distribution, March 1, 1892. This is known as the Stanley transformer patent, issued on an application by William Stanley, Jr., filed August 15, 1888, and has been subject to litigation. On April 26, 1901, Judge Coxe handed down a decision in two suits of the Westinghouse Co. against the Saranac Lake Electric Light Company, alleging infringement of two patents on transformers, one issued to Rankin Kennedy, the other being the present patent. An abstract of the decision in this case was given in our columns in the issue of May 4, 1901. Judge Coxe held the Kennedy patent to be void, and upheld the Stanley patent on the ground that in this patent Stanley first described how to make a regulating transformer. He discovered that he could remedy existing faults by regulating the length of the wire on the primary coil of the transformer and laid down the following rule: "He determines the correct length of the primary coil by winding on wire after the transformer, in circuit, is connected with the dynamo until the loss of voltage represented by the formula C²R equals the predetermined loss of energy to be suffered in the system." The patent came up on appeal from this decision, and Judge Lacombe, on January 14, 1902, wrote an opinion sustaining the lower court. Judge Lacombe stated the Stanley rule as follows: "It says you may determine the proper length of the primary coil by connecting the transformer in circuit with the dynamo with which it is to be used, and then wind on the wire until the loss indicated by the formula C²R within the secondary can equal a certain loss of degree." He also held that this rule is part of the invention disclosed and claimed in the patent. The same patent is now in course of litigation, the defendants being the Montgomery Electric Light & Power Company. On June 18, 1904, Judge Coxe handed down an opinion in this suit again sustaining the patent, holding, first, that Stanley made a valuable invention; second, that the invention is described in the patent with sufficient clearness to enable skilled electricians to practice it without difficulty; and third, that the defendant had appropriated the invention, though its transformers were not designed in the manner pointed out by Stanley. An abstract of this opinion appeared in our issue of July 23, 1904. An injunction was granted but, as noted in our columns last week, the order for the injunction has been reversed on appeal on the grounds that in view of the large importance of the controversy the rights of the party should be reserved for decision until the final hearing of the case, which will come up in due course. In this case the alleged infringing device was a Wagner transformer.

No. 508,188. — Alternate-current electric motor, Nov. 7, 1893. Application filed Oct. 23, 1888. The motor is of the single-phase commutator type, and is similar to a repulsion motor in that the stator field winding constitutes the primary circuit. The secondary (rotor) circuit, however, is not closed upon itself directly, but is connected to a supplemental coil, which surrounds the armature, and through which there flows current, produced by induction from the primary circuit, in a direction to assist the polarizing effect of the current in the armature coils. There are four claims covering the combination shown in the accompanying illustration.

LAMME PATENTS.

No. 519,862. — Method of and means for starting synchronous motors, May 15, 1904. Application filed April 5, 1893. The invention contemplates the applying to the armature of the motor a starting current of low potential and large volume, thereby causing the armature to excite the field magnets by induction, and then gradually increasing the potential of the starting current to that of the supply circuit. The 9 claims, in addition to the general method of operation, cover the means for obtaining the variable potential. This patent is now in litigation, with the Indianapolis, Shelbyville & Southeastern Traction Company as defendant.

No. 582,132. — Alternating-current motor, May 4, 1897. Application filed October 30, 1895. The motor is of the induction type, having a revolving primary and stationary secondary. The invention relates to the construction of the stationary member. A starting resistance of proper value is included in the secondary circuit, and means provided in order to short-circuit the resistance when the motor reaches normal speed. The 15 claims cover the construction of the stator of the Westinghouse Type B motor.

No. 599,940. — Non-synchronous electric motor, March 1, 1898. Application filed April 30, 1894. The invention deals with the shape and size of the primary coils of an induction motor. Each coil of the distributed primary winding embraces an arc which is either greater or less than that resulting from dividing the entire circumference by the product of the number of poles and the number of phases. The object is to produce a sinusoidal distribution of field magnetism. There are four claims.

No. 609,990. — Means for controlling non-synchronous alternating-current motors, August 30, 1898. Application filed March 11, 1896. This patent relates to the use of a variable primary impressed e.m.f. for varying the speed of the motor. The four claims are for the combination with a primary member of a secondary member provided with a comparatively high-resistance winding directly short-circuited on itself, and means for varying the e.m.f. applied to the primary whereby the speed of the motor is varied; a small degree of magnetic leakage between the primary and secondary; means for varying the speed of the motor consisting of a transformer for supplying current to the primary and means for varying the relation between the primary and secondary, thereby varying the e.m.f. supplied by the secondary; and means for varying the active lengths of the transformer secondary, whereby the e.m.f. applied to the primary of the motor is varied.

No. 609,991. — Method of and means for securing constant torque in polyphase motors, August 30, 1898. Application filed February 10, 1898. The motor is of the induction type, and has a comparatively high resistance in the secondary winding and a low degree of magnetic leakage, so that normally its torque increases continually with decrease of speed, and becomes maximum at standstill. In each of the supply circuits is placed a reactive coil, the core of which becomes saturated by a predetermined amount of current, the result being that the torque remains practically constant (at a reduced value) from standstill to that speed at which the current flows, causing the saturation of the cores of the choke coils. There are four claims, the first of which reads as follows: The combination with an induction alternating-current motor having a comparatively high resistance, secondary winding and a low degree of magnetic leakage, of a reactive coil in each of the supply circuits the core of which becomes saturated by a predetermined amount of current whereby a substantially constant torque is secured.

No. 610,067. — Induction motor, August 30, 1898. Application filed July 22, 1897. This patent relates to the construction of squirrel-cage secondary windings for the rotor of an induction motor, and the four claims refer to the use of ventilating blades on the resistance rings.

No. 633,856. — Distributed winding for electrical machines, Septem- ber 26, 1899. Application filed February 6, 1899. The patent relates to mechanical details of the end connectors for the windings, which are covered by 8 claims. J. P. Mallet is a co-patentee. As usually constructed the portions of the armature conductors located in the slots of the core are in the form of bars, the ends of these bars being properly connected outside the core by means of end-connectors of suitable form, which are riveted and soldered or bolted to the ends of the bars.

No. 644,865. — System of electrical distribution, March 6, 1900. Application filed June 14, 1899. The invention refers to the method of obtaining e.m.f.'s lower than the normal voltages of a two-phase system by connecting the coils of the receiver between adjacent leads, or between adjacent single leads and a joint intermediate lead of the supply system. There are eight claims covering the various combinations of e.m.f.'s in quadrature obtainable from symmetrically and unsymmetrically disposed two-phase circuits. The cut shows the method by which can be obtained a voltage seven-tenths of normal value, at which e.m.f. the exciting volt-amperes for an induction motor, when lightly loaded, will be approximately one-half of the normal.

No. 759,183. — Method of utilizing single-phase, alternating-current energy, May 3, 1904. Application filed December 26, 1901. The invention refers to the use of the commutator type of single-phase motor, which was described fully in our issue of February 13 of last year. There are 8 claims relating to the proper proportioning of the field and armature windings.

HUTIN AND LEBLANC PATENTS.

No. 592,272. — Alternating-current electrodynamic machine, November 13, 1904. Application filed August 20, 1892. The invention relates to damping devices for preventing oscillations in the speed of synchronous motors and generators. There are six claims which cover the use of paths of low electrical resistance located within the path of the magnetic flux of the machine, at the margin of the interpolar space. This patent is now in litigation, the Bullock Electric Manufacturing Company being defendant.

No. 553,469. — Alternating-current motor, January 21, 1896. Application filed November 17, 1892. According to the patent, the secondary resistance of an induction motor is to be decreased in direct ratio with the frequency of the secondary circuit, so as to maintain the rotor torque at a constant maximum whatever may be the speed of rotation. Although the resistance is to be varied mechanically and the five claims cover means for producing the variation, the specification discloses no means other than the manual operation of a rheostat.

No. 12,223 (reissue). — Alternating-current transformation, May 24, 1904. Original, No. 754,371, March 8, 1904. There are two separate transformers in which the individual magnetic fluxes are in time quadrature. Two-phase e.m.f.'s may be obtained (or supplied) by winding similar coils on the cores of the two transformers, while three-phase e.m.f.'s may be supplied (or obtained) by passing around one of the magnetic cores for one of the three phases a number of turns proportionate to the sine of a certain arbitrarily chosen angle, and around the other core a number of turns proportionate to the cosine of the same angle; and for the other two phases using numbers proportionate to the sine and cosine of the same angle plus 2π/3, or minus 2π/3, respectively. The six claims cover the method in general without reference to specific apparatus.

DUSINBERRE PATENTS.

No. 763,379. — Alternating-current induction motor, June 28, 1904. Application filed February 27, 1904. The starting resistance of the revolving secondary is mounted in the form of a helix concentric with the shaft of the rotor, and variation in the effective length is accomplished by means of a contact device movable longitudinally upon the shaft. There are 12 claims covering the constructive details.

No. 763,547. — Alternating-current induction motor, June 28, 1904. Application filed February 27, 1904. The invention relates to means for automatically decreasing the resistance of the secondary circuit as the speed increases. The auxiliary resistance is assembled in spiral form and mounted so as to rotate with the motor shaft, which shaft also carries a contact device operated by centrifugal force whereby the amount of resistance included in the secondary circuit is decreased with increase of speed. The four claims cover the constructive features.

NOLAN PATENT.

No. 582,481. — Fastening means for core plates of electrical machines, May 11, 1897. Application filed January 20, 1897. In a circumferential groove in the core spider there is placed a spring metal ring which extends outside the groove and against a shoulder on an annular plate between which and a flange on the core the laminæ are clamped. The construction is illustrated in Fig. 5 and is covered by four claims. This patent is now in litigation, the Bullock Electric Manufacturing Company being defendant.