US469441A - Electro-magnetic reciprocating engine - Google Patents

Description

4 Sheets-Sheet 1 (No Mac 161.)

M. J.,'WIGHTMAN.- 1521-.BG'I3R0 MAGNETIC REGIPROGATING ENGINE,

0. 469,441. Patented Feb. .23, 1 92;

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' 'M. J. WIGHTMAN ELECTED MAGNETIG REGI'PROGATING ENGINE. No.'469,441.

Patented Feb. 23, 1892.

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ELBOTRO MAGNETIC REGIPROOATING ENGINE. .No. 469,441. Patented Feb. 23, 1892.

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(No Model.) 48heets-Sheet 4.

M. J. WIGHTMAN... ELEGTRO MAGNETIC REOIPROGATING ENGINE. No. 469,441..

Patented P011 23, 1892.

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MERLE J. WIGHTMAN, OF SCRANTON, PENNSYLVANIA.

ELECTRO-MAGNETIC REC-IPROCATING ENGINE.

SPECIFICATION forming part of Letters Patent No. 469,441, dated February 23, 1892.

Application filed February 5, 1891. Serial No. 380,269. (No model.)

To all whom it may concern:

Be it known that I, MERLE J. WIGHTMAN, a citizen of the United States, and a resident of Scranton, in the county of Lackawanna and State of Pennsylvania, have invented certain new and useful Electro-Magnetic Recip rocating Engines, of which the following is a specification.

The object of this invention is to produce a powerful and compact electro reciprocating device for any purpose in which a reciprocating motion is desirable.

A further object of the invention is to secure a perfect control of such reciprocating device, making it possible to alter the length of the stroke, the number of strokes per minute, and the relative strength of the force of the going and returning motion.

My invention is especially applicable to reciprocating" electro -magnet.ic drills; and it consists, first, in the construction hereinafter described and claimed, whereby a magnetic circuit for the part which I shall term the armature of the machine is furnished almost entirely through iron, as hereinafter described, and then specified in the claims.

My invention consists, further, in a reciprocating electro-magnetic engine in which reciprocation of a movable core or armature is produced by a novel combination of coils in which continuous and alternating electric currents flow, as hereinafter more particularly described and claimed.

My invention consists, also, in novel methods and means for controlling the action of the apparatus for the purpose of altering the length of stroke, the number of strokes, and the relative strength of the forward and return stroke, and in other details of construction and combinations of parts, as hereinafter more particularly described and claimed.

In the accompanying drawings, Figure 1 is a longitudinal section through an apparatus embodying my invention, and also illustrates diagrammatically a means for obtaining the continuous and alternating currents from the same primary source. Fig. 2 illustrates, diagrammatically, a means which may be employed for altering or determining the relative strength of the going and return strokes of the oscillating member of the machine. Fig.

8 illustrates a modification in the disposition of the coils which excite the armature and fieldmagnet of the machine. Fig. 4 is a diagram showing the different conditions of the magnetic wave under different adjustments of the relative strength of the continuous and alternating magnetizing influences. Fig. 5 illustrates an extension of the number of coils in the machine to get increased force. Fig. 6 illustrates, diagrammatically, a means for controlling the relative strength of the going and return strokes. Fig. 7 illustrates a modification in the means for producing the magnetic field for the reciprocating armature-core. Fig. 8 illustrates diagrammatically, a method and means for determining the length of st'roke. Figs. 9, 10, 11, and 12 illustrate, diagrammatically, other modifications to be hereinafter more fully described. Fig. 13 is a cross-section through the iron cylinder on the line of one of the coil-holding grooves.

Referring to Fig. 1, 0 indicates an iron tube, shell, or case made in one or more longitudinal sections fastened between the heads A A within which shell, case, or cylinder the iron core or plunger B, fitting the bore of said case, reciprocates. The core B may be connected directly or indirectly to the tube or other instrument to be operated upon and forms in the organization hereinafter described the element of theelectro-magnetic reciprocating engine that may for simplicity be termed the armature of the machine.

The core B is furnished with one or more exciting-coils, such as a, which are let into a groove in said core, have a magnetic axis coincident, substantially, with the longitudinal axis of said core or armature, and are flush or sunk below the outer cylindrical surface of the core, so that the iron of the latter may be at all times in close proximity to the iron of the cylinder or case 0. The core A is by preference a laminated core-that is to say, is subdivided in the direction of its magnetic axis in order that when excited by alternating currents it may readily change its magnetic condition.

The core B may be guided by suitable stems or rods cl (1, projecting from it at opposite ends, and said stems may be utilized as the means for conveying the exciting-current to the coil or coils of the core B. For this purposeI propose to insulate one of the heads, as A, from the iron shell or case 0, as shown, by suitable insulation, thus insulating it from the opposite head A in which the stem (1 slides. The stem (1, attached to the core B, is insulated from said core and therefore is electrically insulated from the stem (Z, which is attached directly to the core. If now the terminals of the coils on the core be connected one to the body of the core or to the stem (Z and the other to the stem d, it is obvious that by making the electrical connection with the guides in which said stems move current from any source may be passed into and out of the coil. The connection may be made either directly to head A or to the body Connection to the opposite terminal or pole of the circuit is made from the head A, as clearly shown, and, if desired, the formation of elec trical connection with the stems may be assisted by using a spring or springs bearing on the stems, as indicated at (P.

The exciting coil or coils which form the field-coils of the machine are applied in grooves or recesses formed at the inside of the iron shell or case 0, as clearly shown in Fig. 1. These coils are applied so that their inner diameters shall be equal to or somewhat greater than the smaller inner diameter of the case (J; or, in other words, they do not project radially inward beyond the iron of the case 0. It will be observed that by this construction the iron of the core is at all times close to the iron of the case and that any magnetic circuits from one pole to another of the iron core are through the iron of the fieldmagnet made up almost entirely of iron.

In constructing the instrument the coil or coils lying on the interior of the case or shell 0 are first wound and the sectional core applied over them and the sections fastened in the proper relative position by attachment of the heads A A \Vhen the machine derives both its armature and its .field excitation from the action of the coils, it comprises, fundamentally, three elements-to wit, two field-coils and one armature-coil or two armature-coils and one fieldcoil-this fundamental orsimplest form of the invention being obviously capable of extension to a large number of field and armature coils combined, however, substantially in the manner in which the three elements herein described are combined.

In the subjoined description the stationary coils are spoken of as field-coils and the movable coils as armature-coils. The two coils may be likewise regarded as sections of a single coil so spaced and arranged, however, and so connected to theirexciting-circuits that when traversed by the exciting-current there will be at any given instant a consequent pole produced between them in the iron of the shell or the core. The coil or coils constituting the field element or field-coils of the machine and the coil or coils which form the ar- In the arrangement shown in Fig 1 the field coil is made in two sections 12 I), when there is but one armature-coil a. The obvious modification of this arrangement (illustrated in Fig. 3) would comprise two armature-coils a a and one field-coil b. The action of the two coils or section of coil b b in Fig. 1 when traversed by a current of any given polarity is to form an intermediate consequent pole and exterior poles of polarity (indicated by the letters N S) in the iron of the case or shell 0. If then the coils l) b be traversed by a continuous current of proper polarity to produce the magnetic polarities indicated and an alternating current be circulated in the armature-coil a, so as to produce polarities of alternately-opposite sign at the opposite ends of the core B, the result will be an oscillation of said core and coil due to the changing attractions and repulsions between the armature and the field. It will be quite obvious that the same action would be produced if a continuous current circulated in the coils a and an alternating current in the coils i) Z), and also that the same action will be produced in the arrangement shown in Fig. 3 whichever elementof the apparatus be traversed by the continuous or alternating currents.

The construction heretofore described is the simplest form of my invention; but, as will be obvious, the armature and field coils might be multiplied, as indicated in Fig. 5, giving a result the same as if a number of devices like that in Fig.1 were arranged end to end to operate as one powerful engine. By the arrangement shown in Fig. 5 it is possible to obtain a short and very powerful oscillating effect and by properly increasing the number of coils it is obvious that a'strolce of almost unlimited force can be obtained.

To operate the machine the continuous and alternating currents required may be derived from any desired source, and it would be within my invention to produce the oscillations by taking a continuous current sup plied from any prime generator and interposing a current-rcversing appliance in the circuit between the same and the element of the machine in which reversals of magnetism are required, such continuous current generator, combined with the polechanger, forming together the source of alternating currents. I prefer, however, to obtain the alternating and continuous current from the same prime source, consisting of the arma- IIO IIR

ture of a dynamoelectric generator or ma-' chine, for which purpose I employ an organization which is illustrated diagrammatically in Fig. 1 and which comprises, essentially, an armature having a closed electric circuit for its coils, such as the windings of a Gramme armature or a Siemens armature, in combination with the usual commutator, from which continuous currentsmay be supplied and fixed or permanent connect-ions taken from points in the Winding of such armature where there isa difference of electrical potential, such permanent connections being led through suitable rings and conductors to the alternating-current portion of the apparatus.

I have illustrated diagrammatically an arrangement suitable where a Gramme armature is employed. The field-magnets of such an armature are indicated by the letters G G and the armature of the machine by theletter IL. The brushes of the continuous-current commutator are typified at I 1 the commutation being eifected by the contact of such brushes with the coils of the continuous winding in succession as they move with the rotating armature-core. This arrangement is merely typicalof anyclosed-circuit or Gram me armature wherein a commutator of the usual construction is provided for taking oil? the continuous current, and it will be understood that in practice a commutator of any ordinary or suitable form would be employed. The brushes I I connect to the part or element of the machine, as coils b b, in which the continuous currents are to flow. A suitable current-controlling device consisting of an artificial resistance or other mechanism is typified at h and is interposed, as indicated, in the circuit of the coils b b. Permanent connections to the alternating-current portion of the apparatus from points of the closed armature-winding, as l0 10, which are of different potential, are furnished by means of collecting-rings gf, insulated from one another and connected, respectively, with the two points 10, and by brushes gf', bearing on said rings continually and themselves connected to the circuit of the coil a, in which alternating currents are to flow. I

It will be obvious that alternating currents are collected from the armature as from an ordinary generator, there being two alternations when the two field-poles are employed for each whole revolution of the armature. At the same time the same armature will be furnishing the required continuous current for exciting one element or portion of the machine. The alternating current furnished may pass through a suitable controlling device consisting of a rheostat i or other means for regulating the current.

a To obtain a variable number of oscillations per minute of the core B an ordinary motorarmature might be used in place of the generator-armature and the speed of the motor varied according to any of the well-known methods, as indicated in Figs. 11 and 12, to be presently described.

A special and important feature of my invention consists of the method which I have devised for varying or adj usting the relative strength of the strokes of the engine in opposite directions. By myinvention the strength of the stroke in one direction may be made stronger than in the other and may be ad justed to any desired strength. This is especially useful in reciprocating rock-drills. It is obvious that when the instrument is operated by alternations of magnetic polarity in one or the other element of the instrument produced by the alternating currents having equal positive and negative value the stroke of the piston or armature would be equal in both directions.

My invention consists in compounding the excitation of one or the other element of the machine with a continuous and an alternating magnetizing influence and varying the relative strengths of such influences, as hereinafter described, so as to vary the relative strength of the positive and negative resultant magnetizations which respectively produce movement in the two opposite directions; or, in other words, I sub ect the alternating portion of the machine to a continuous magnetizing influence of one polarity, superposed upon which is an alternating influence, and vary the strength of one or the other,or both, as desired,.to change their relative strengths, with I( o the result of changing the force with which the oscillating member of the machine moves.

I have illustrated this feature of my invention in Fig. 2, as carried out in connection with an organization wherein the oscillating memher, as the armature or core B,is one in which the alternations of magnetic polarity are produced, and for the sake of simplicity shall further describe the invention as carried out by giving said armature a certain continuous I TO magnetization of fixed amount and superposing upon this magnetization an alternating magnetic force or influence produced by the alternating currents and of variable amount.

As will be seen from thediagram, the arma- I 15 titre-coils a, being connected in series with the coils b b, which are connected to the continuous-current source, will be themselves. traversed by a continuous current, which will be assumed to be of substantially constant effect. Passing also through said coils a is a local alternating current derived from the source f" g and regulable in amount by means of regulator 71. By thismeans there can be produced an excitation in the armar25 ture-field, which would be represented by the curve, Fig. 4. If the magnetizing effects of the continuous and alternating currents upon the core B are equal, the curve would take the form indicated at A 13 which means that 1 0 the magnetism does not reverse in the armature, but simply rises and falls from and to zero. If now the alternating current be in-' creased in strength by the adjustment of i,

the return or reversing magnetism may be made to rise to any degree desired. A slight reversal of magnetism might be suflicient to bring the armature into position ready for the blow, and the strength of the blow as com pared with the recovering force would be as the area inclosed by the curves C D on one side of the zero-line and F F on the other.

It is quite obvious that the same effect would be produced by diminishing the continuous current instead of' increasing the alternating current or that the same action would ensue from the simultaneous adjustment of the strengths of the two magnetizing influences to change their relative strength and permit the alternating currents of the sign which opposes the continuous current to overcome such continuous current, so as to produce an actual reversal of magnetic condition in the armature. that by thus differentiating the influence which is of constant eifect or tends to give the core B a magnetism of the same polarity with an alternating influence and varying the relative strengths of such influences, s6"

as to give to the alternating influence of either sign a predominating effect, the force of the blow or stroke in one direction or the other may be varied or adjusted, as desired.

It is obviously not necessary that the continuous magnetizing influence should be applied to the core B or to other part of the instrument by means of the same coil through which the alternating currents produce their effect, and the armature might for the purposes of this part of my invention be wound with two separate coils, one carrying the continuous and the other the alternating current; or the magnetizing influence which tends to produce a magnetism continuously of the same polarity or sign might be a permanent magnetism.

Fig. 6 illustrates a modification of my invention wherein the two coils or sections of coil 1) b are traversed by an exciting-current from any source, as I 1 in multiple. In a connection between the two branches in which said coils lie is an artificial resistance R provided with means, as a regulating-lever R for connecting any part of the resistance to .the continuation of the circuit, and thereby adjusting the relative flow of current in the two sections Z) Z). This affords a simple means whereby the relative strength of the two coils or sections of coil 1) b may be varied and the relative strength of the forward and return stroke of the core thereby adjusted. It is obvious that the two sections of coil Z) Z) might be either the field or the armature coils, though, for constructional reasons, it is preferable to make them the field-coils. It will also be obvious that either the coil a or the coil 1) Z) may be traversed by the continuous current, the other being traversed by the alternating current.

Fig. 7 shows a modification of my invention wherein the magnetic field is produced It will be obviousby two permanent magnets L L, having the polarities indicated and closely embracing the reciprocating armature-core B. The polarity so provided by these permanent magnets is obviously the same as that which would be produced by the single coil 1), Fig. 3, and the iron of said magnets furnishes the magnetic circuit'for the magnetism developed in the iron of the core B by the coils therein.

Fig. 8 shows an arrangement whereby the oscillation of the armature or the length of the stroke in one direction can be varied or adjusted. The field-coil, as indicated, is divided into a large number of sections, which are connected in series to a number of switch contact plates or points 25, the terminals of the sections of coil being,'however, connected to one pole of a suitable generator. An intermediate portion of the coil may be connected to the other pole of the generator by means of a movable switch, the contact-spring of which'is indicated at M, said spring being mounted on a movable block moving on a slide and being connected, as indicated, to the generator. Itis obvious that a polarity of substantially the same nature as indicated in Fig.1 will be produced in the iron of the case 0 and that the position of the pole N will vary with the position of the spring M. I have shown the field-coils in this case as supplied from the continuous-current source, while the coil a on the armature is supplied from the alternating-current source; but it is obvious that the arrangement might be reversed. The shifti-ng of the brush M will obviously determine the position of the fieldpoles relatively to the core B.

Fig. 9 illustrates a way in which the eXcit-' ing-coils of one portion of the apparatus may be used as a reactive resistance for the alternating currents exciting the other portion. The armature-coil a is supplied from any source, as indicated, with an alternating electric current, While the coils Z) Z), forming the field-coils, are supplied from any continuouscurrent source. In the circuit of the alter nating-current source is a greater or less portion of the field-winding b, as indicated, and more or less of said winding is introduced into the said circuit by means of the switchlever S moving over contacts connected to sections of said coil. The reactive induction or kick set up in said coils b to the alternating currents may by this means be varied to adjust the strength of the alternating currents supplied through the armature-coils a.

Fig. 10 illustrates a modification in which the source of the alternating currents consists of a continuous-current generator combined with a pole-changer. The prime generator is any source of continuous currents, and the pole-changer, of any suitable type, (indicated at R is placed in the circuit between said generator and the portion of the apparatus in which an alternation of the exciting influence is to be produced. The polechanger is mechanically operated by suitable l'IO connection with the reciprocating portion of the apparatus-es, for instance, the core B.

The coils on said core are connected to secof the polarity induced therein by the coils is shifted also, so that the relative location of armature and field polarity is maintained and the repulsive effects are produced with the maximum efficiency at all positions in the movement of the core.

Figs. 11 and 12 illustrate the manner in which the alternating currents may be obtained from a continuous-current or closed circuit armature when the latter is used as the armature of a motor. G is a source of energy, as a dynamo-machine, which supplies the current for running the motor. The continuous-current coils b b are fed from said generator, as indicated, through a con trolling-resistance h or other governing device. The armature H of the motor and the field-magnet coils for said motorare included in a circuit through which current is passed from the generator G. In this instance the motor-armature turns under theaction of the current circulating in the field and armature, and the speed of the motor may be changed by means of a variable resistance R included in the circuit of the field. The alternatingcurrent portion of the circuit is fed, as before, by means of the continued connection with points 1O 10 of different potential in the closed circuit of the armature-coils. The revolution of the motor-armature will, it is obvious, cause alternating currents to be furnished through the brushes f g to the circuit in which the alternating currents are required, while at the same time a continuous current flows through the commutator portion of the armature-circuit, which is connected to the mains or wires in which the continu-' inspection, one circuit fed from the mains or wires kept at constant potential or substantially constant potential by the generator Gr includes the closed-circuit armature H and the coils b I), while another circuit fed from said mains includes only the fieldmagnet coils of the motor and the regulator of the speed R That particular combination of apparatus illustrated in Figs. 11 and 12 designed to supply the combined alternating and continuous currents from the same general source, as well as the arrangement for varying the relative strength of the going and return stroke illustrated in Fig. 0, are not herein .claimed, as they form the subject of claimsin another application for patent filed by me July 15, 1891, Serial No. 399,571, as a division of the present application.

What I claim as my invention is 1. In an electro-magnetic reciprocating engine, an iron cylinder and an iron core fitting the bore of said cylinder, in combination with electric coils in grooves or recesses in the interior of the cylinder and the exterior of the core, respectively.

2. In an electro-magnetic reciprocating engine, the combination, with the movable core carrying an exciting-coil, of guide-stems projecting from opposite ends thereof and insulated from one another, said stems being connected, respectively, to the opposite ends of the coil-circuit on said core.

3. In an electro-magnetic reciprocating engine, the combination, with the movable core carrying an exciting coil or coils, of the stems projecting from opposite ends of said core andinsulated from one another, and the guideheads for said stems insulated from one another and connected with the poles of the supply-circuit.

4. The combination, substantially as described, of the reciprocating core carrying an exciting-coil, an iron shell surrounding the same, the heads A A insulated from one another, and the stems cl d, projecting from opposite ends of the core and insulated from one another, said stems being connected, respectively, to the terminals of the exciting coil or coils on the core.

5. In a reciprocating electro-magnetic en gine, the combination, with the reciprocating magnetic core, of an exciting coil or coils 111 a groove or grooves upon the same, anda fieldmagnet consisting of an iron cylinder which closely embraces said core and is provided with an internal groove or grooves for the field-coi1s,'as and for the purpose described.

6. In an electromagnetic reciprocating engine, the combination, with an iron casing having coils in a groove on its inside and an iron core reciprocating therein and having coils on its outside, of a continuous-current source connected to the coils of one and a prime generator of alternating currents connected to the coils of the other.

7. The combination, with the iron cylinder made in one or more sections divided from one another on lines parallel to the axis of the or more coils on both portions of the apparatus, the coils on one portion having a contin- ICC nous excitation and the coils on the other an alternating excitation.

8. In an electro-magnetie reciprocating engine, the combination, wit-h an iron cylinder made in two or more longitudinal sections and having one or more interior grooves or depressions, of an iron core having an exterior groove or grooves, coils in the grooves of the cylinder or core applied to produce consequent poles in the iron between the grooves, and means for furnishing an alternating current to the coils on one portion of the apparatus and a continuous current to the coils on the other portion.

9. In a rock-drill, the combination of a fixed iron cylinder having an interior coil-carrying groove or grooves formed in the iron of the cylinder and a reciprocating tool-actuating core having one or more exterior coil-carrying grooves.

10. The combination, with an electric motor having a continuous-current field-magnet and an alternating-current armature, or vice versa, of a continnous-current generator having a closed-circuit armature and commutator supplying the continuous'current portion of the motor, and continual or permanent connections from points of the closed armature-circuit of different potential to the alternatingcurrent portion of themotor forsupplying an alternating current thereto;

1]. The combination, with a reciprocating engine or motor having field-magnet and armature circuits supplied by continuous and alternating currents, of a continnous-current generator having a closed-circuit armature and commutator connected to the continuouseurrent circuit, and permanent connections from points of the armature-circuit of different potential to the alternating-current circuit of the engine.

12. In an electro-magnetic reciprocating engine in which one of the elements of the machine has a continuous and the other an alternating magnetism, the herein-described method of varying or adjusting the strength of the stroke in one direction or the other, consisting in super-posing the alternating influence upon a continuous magnetization of one polarity and varying the strength of the alternations to change the relative strength of the forward and return stroke.

13. The herein-described method of varying the relative force of the forward and return stroke in a reciprocating electro-magnetic engine, consisting in compounding the excitation of one or the other element of the machine with a continuous and an alternating magnetizing influence and varying their relative strength, as and for the purpose described.

14. In a reciprocating engine, an armature having a magnetic stress or bias continually tending to make the same of one polarity, in combination with a magnetizingcoil for said armature traversed by alternating or reversed currents, and means for varying the strength of said alternating currents.

15. The herein-described method of obtainin g a difference between the forward and back strokein a reciprocating engine having a con-- tinuous field and an alternating armature, consisting in giving the armature an excitation of constant polarity from any source and varying the relative strength of the constant magnetizing influence and an alternating influence which produces in said armature alternations of magnetic polarity.

1b. In a reciprocating electro-magi'ietic engine operated by variations of magnetism in one or the other element of the machine, the combination, with the alternating element having a magnetic stress or bias continually tending to make the same of one polarity, of an alternating-current coil acting on said element, and means for changing the relative strength of the forces tending to alternate the magnetism and to keep the magnetism of the one polarity, as and for the purpose described.

17. In a reciprocating electro-magnetic engine system, the combination, with the same element of the machine, of a continuous-current source, an altcrnating-current source, and means for varying the relative strength of said currents, as and for the purpose described.

18. In an electro-magnetic reciprocating engine, the combination, with an armature and field-magn et, one of which hasa coil traversed by a continuous current and is constantly of the same magnetic polarity, of a continuouscurrent source and an alternatingcurrent source, both connected to a coil or coils upon the other, and means for varying the relative strength of said currents, as and for the purpose described.

19. The combination, with an electric motor having a continuous-current field and an alternating-current armature, or vice versa, of a closed-circuit revolving armature and commutator therefor, having connections from the wires leading to or from the continuous-current portion of the motor, and continual or permanent connections from points of the said' closed armature-circuit of different potential to the alternating-current portions of the motor for supplying an alternating current thereto, as and for the purpose described.

20. In a reciprocating eleetro-magnetic engine, the combination, with a sectional fieldcoil having its terminals connected to one pole of the generator, of means for connecting the other pole of the generator to various intermediate points of the series of coil-sections.

21. In a reciprocating electromagnetic engine, the combination, substantially as described, of a'sectional field-coil wound and connected to have a consequent pole, an armature having an exciting-coil, means for supplying an alternating current to one coil and a continuous current to the other, and an exciting-coil, a series of coils surrounding the same and Wound and connected to produce a consequent pole, an alternating-current source connected to the coils of one element, a continuous-current source connected to the coils of the other element, and means for varyin g the connections of the series of coils, so as to change the position of the polesproduced thereby.

24. In an electro-magnetic apparatus having coils in separate circuits traversed, respectively, by alternating and continuous currents, a reactive resistance for the alternating currents of one circuit, consisting of coils in the other circuit, as and for the purpose described.

25. In an electromagnetic reciprocating-engine system, the combination, substantially as described, of a coil or set of coils exciting one element of the device by continuous currents, a coil or set of coils exciting the other element by alternating currents and having circuit through the first-named coil, and inde-' pendent sources of alternating and continuous currents, as and for the purpose described.

26. The combination, substantially as described, of the reciprocating core havinga coil traversed by alternating currents, and the fixed coils traversed by continuous currents and also by the alternating currents flowing in the first-named coil.

Signed at Scranton,in the county of Lacka- Wanna and State of Pennsylvania, this 31st day of January, A. D. 1891.

MERLE J. WIGHTMAN.

Witnesses:

HORACE E. HAND, H. BERGHOLTZ.

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