US2203695A

US2203695A - Reciprocating electric motor

Info

Publication number: US2203695A
Application number: US759508A
Authority: US
Inventors: Thomas J Murphy
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-12-28
Filing date: 1934-12-28
Publication date: 1940-06-11
Anticipated expiration: 1957-06-11

Description

June 11, 1940. rr. J. MURPHY RECIPROGATING ELECTRIC MOTOR 2 Sheets-Sheet 1 Filed Dec. 28. 1934 INVENTGR BY y ATTORNEYS Flgfi 49 4a 44 43 June 11, 1940.

T. .1 MURPHY RECIPROCATING ELECTRIC MOTOR Filed Dec. 28. 1934 2 Sheets-Sheet 2 g/|NVENT0R ATTORNEYEZ Patented June 11, 1940 UNITED STATES PATENT OFFICE RECIPROCATING ELECTRIC MOTOR Thomas J. Murphy, Stamford, Conn.

Application December 28, 1934, Serial No. 759,508

14 Claims.

This invention relates to a razor blade sharpener. particularly one operated by an electric current for sharpening safety ,razor blades.

It is an object of the invention to provide a sharpener of this type which is small and easily portable, and can be readily held in the hand and plugged in to any standard outlet of a house wiring system for operation.

Another object is to provide such a sharpener which will sharpen a blade in a rapid and accurate manner, and produce a superior cutting edge.

A further object is to provide an improved operating mechanism which does not require any rotating elements or make and break devices, and therefore will operate indefinitely, will be of simpler construction, and furthermore will operate with less vibration and less noise than devices employing such features.

Other objects will become apparent from the following description taken in connection with the accompanying drawings, it, however, being understood'that variations and modifications may be employed within the principles of the invention and the scope of the appended claims.

. In these drawings:

Fig. 1 is a vertical transverse section substantially on line l-l of Fig. 2;

Fig. 2 is a top plan view with certain parts broken away to more clearly show the construction, the section of the vibrating element being substantially on line 2-2 of Fig. 1;

Fig. 3 is a longitudinal vertical section taken substantially on the line 3-4 of Fig. 2;

Fig. 4 is a top plan view of a blade holder on an enlarged scale;

Fig. 5 is a detailed section thereof substantially on line $-5 of Fig. 4;

Fig. 6 is a detailed plan view of one mounting for the pivot of the blade support;

Fig. 7 is a section through one of the sharpening tables substantially on line 1-1 of Fig. 2;

Fig. 8 is a top plan view of one end of an armature;

Fig. 9 is a section substantially on line 9-4 of Fig. 3 showing various elements in elevation and with a portion of the casing broken away to show one of the vibrating elements;

Fig. 10 is a detailed section substantially on line ill0 of Fig. 3;

Fig. 11 is a horizontal section substantially on line ll-Ii of Fig.8;

Fig. 12 is a diagrammatical view showing the arrangement of the armatures with respect to the magnetic cores; and

Fig. 13 is a diagrammatical view showing a somewhat modified arrangement.

The device shown on the drawings on an enlarged scale comprises an enclosing casing ii of any suitable material such as metal or a molded material such as a phenolic condensation product. This casing has an open upper end which is closed by a cover I. As will be seen the casing encloses all the elements except the two vibrating or reciprocating elements carrying the sharpening tal0 bles, and the holder for the blade being sharpened, these elements being exposed on the top of the cover where they are easily accessible and where the sharpening operation can be readily controlled and observed.

The device in the broadest sense comprises two opposed sharpening elements reciprocating synchronously in opposite directions and arranged to respectively operate on the bevels on the opposite sides of the cutting edge of a safety razor blade 20 which is held in such a way as to be pressed against the surfaces of the sharpening elements alternately and at the proper angle for best cutting eil'ect, and to grind or burnish the entire length of the cutting blade uniformly and in the 25 same manner.

On the opposite sides of the cover ii are upwardly extending lugs I1 and I0 forming bearings for a longitudinally slidable and turnable blade holder supporting shaft I! provided at one end 30 with a hand knob 20 to be grasped between the thumb and finger for sliding and turning the shaft I! in its bearings I1 and it for a purpose later to be described. Mounted on this shaft is a holder for the blade being sharpened. This 35 holder comprises a bodyor support 2| and a clamp 21 pivoted to the body 2| by any suitable means such as a hinge 23 at one end. This body or support 2| is mounted on the shaft is by means of a curved central ear 24 which embraces the 40 shaft but has an internal diameter somewhat larger than the diameter of the shaft so as to be loose on the shaft and permit the holder to have limited oscillating movement about an axis at right angles to the axis of the shaft. This lug is I secured to the shaft so as to turn with it and to have this limited oscillating movement by means of a pin 25 projecting from the shaft through an opening in this car. The body II also carries ears 28 spaced on opposite sides of the ear 2i and 50 forming stops to engage the shaft and limit the oscillating movement of the holder. This body and-cover may be stamped from sheet metal, if desired. The body is provided with locating lugs or studs 21 to fit in the openings in the razor blade 28 to properly locate the blade, and when the cover or clamp 22 is in clamping position they project through correspondingly located openings 29 in the clamp 22. These locating studs insure that the blade is always held in the holder in the proper position. At the opposite end from the hinge 23 the clamp is provided with a spring clip 38 to engage over the opposite end of the body to hold the clamp in closed position, and this clip is extended as indicated at 3| to form a finger grip. When it is desired to release the blade all that is necessary is to press with the thumb on the stud 21 and lift up on finger piece 3| with the finger. This will open the clamp after which the blade may be easily removed. If desired, a dowel pin 2Ia is also provided on the body 2| extending into the clamp 22 and through an opening in the blade. It is located nearer one of the studs 21 than the other. This makes sure the blade is always put in the sharpener in the same manner so angles on blade edge will be kept perfect.

The blade is sharpened by resting alternately on two reciprocating tables 32 mounted below and on opposite sides of the shaft [8. These tables are so located that when the shaft 18 is turned so that the cutting edge of the blade rests on one of these tables the blade is inclined at the proper angle, as indicated in Figs. 1 and 9, to correspond with the proper bevel "on the opposite sides of the cutting edge. These two tables are mounted on blocks 34 by any suitable means such as screws 35, which blocks are each in turn supported on upright spaced parallel spring elements 38, preferably of substantially flat strips. The table block 34 is recessed on its opposite sides as indicated at 31 to receive the upper ends of these spring elements, and the blocks are secured to these elements by any suitable means such as the rivets 38. This provides a portion of the block between the spring elements against which they are clamped so that the bending in the springs is at the lower edge of the block instead of at the rivets, which would tend to cause the connection to work loose. These blocks extend through openings 39 in the cover l8 so that the tables 32 are supported above this cover, the openings 39, however, being of sufilcient size to permit the desired oscillating or reciprocating movement of the tables and the blocks. Secured to the underside of each of these blocks is an armature 40 of any suitable magnetic material such as soft iron, and is secured to the blocks by any suitable means such as the screws 4|. The armature is generally of rectangular cross section and has a central opening through which the spring elements 38 pass and in which the reduced portion of the block between the recesses 31 is located as shown in Fig. i. This therefore helps to hold the spring elements against the sides of the blocks and insure bending of the spring at the lower side of the block and the armature instead of at the rivets.

The spring elements 38 are clamped and supported at their lower ends by a transverse bolt 42 to a support 43 which is fastened to the lower end of the casing l5 by any suitable means such as a screw 44. Clamped between the inner spring element and the block on each side thereof are the ears 45 of a core support 48, and against the outer spring element 38 is a support clamp 41 which is of general U-shape to embrace the springs, the ears 45 and the supporting block 43, and are clamped thereon by the bolt 42. The free ends of the legs of the clamps are provided with ears 48 which are secured together by any suitable means such as the screws 48. With this arrangement the various elements are all securely clamped to the support 43.

It will be noted from Fig. 1 that the spring elements 38 are mounted in spaced relation with a stop element 58 between them and extending from their lower supported ends upwardly for a suitable distance between the two spring elements. The spring elements are, however, spaced from this element 50 a suitable distance by spacers 5| which may be in the form of square washers. The member 50 may be provided with an elongated slot 52 whereby it may be adjusted up and down to vary the magnitude of vibration of the spring elements or reciprocation of the tables 32 as will later be described.

Located between and at the outer sides of the vibrating spring elements 38 are mounted

laminated cores

53 and 54 of good magnetic material such as soft iron, and they are preferably of substantially E-shape to provide center poles or

legs

55 and 58 and outer poles or

legs

51 and 58. The upper ends of these poles or legs are adjacent the armatures 40, the armatures being spaced a short distance above the tops of these legs. These cores are clamped together by transverse bolts or rivets 59 passing transversely through them, and the two outer cores 53 are held in proper spaced relation from the intermediate core 54 by suitable spacers 80 which may be strips of sheet metal with their ends bent around the rivets 59 as indicated at 8| in Fig. 3. These cores are mounted on a pair of supports 48 which have spaced side members 82 located on opposite sides of the intermediate core 54 to which they are clamped by any suitable means such as the rivets 83. They also include laterally extending ears 48a located between the ears 48 and between which they are clamped by screws or bolts 49. (See Fig. 10.) By this arrangement it will be seen that the cores and associated parts are securely mounted on the supporting block 43. Also, at the upper ends of the legs 58 are other supports or brackets 89 which have a body portion 80 clamped on the outside of the outer poles 58 by transverse rivets 9! which also clamp the cores together. There is one support 88 for each pole or leg 58 giving four in all. Each support also has an ear 92 to which the cover 18 is secured by screws 93. The body portion 90 is also provided with lugs 94 extending at opposite sides of the legs 58 to hold the supports in upright position. By this arrangement the elements are all secured together and to the cover and casing, and by tightening screw 44 the cover is clamped on the casing and all the parts securely held against rattle or shifting out of position in the casing.

Embracing the

center legs

55 and 58 of the cores is a coil 84, this coil being connected by

suitable leads

85 and 86 to a source of A. C. supply, these leads being an extension of the leads in any suitabe type of cord 81 having a plug-in cap (not shown) for plugging into any suitable outlet from a house wiring system in a manner well known. In one of the leads, as the lead 88, is located a control switch 88 of any suitable type, that shown being of two

spring elements

88 and 18 having contact points H and mounted on a suitable insulating support. In that shown there is a bracket member 12 clamped to one of the outer cores by the lower rivets 59, this bracket forming a support for the switch. It has a laterally extending arm !3 to which the spring members or arms 39 and 10 are mounted as by a screw 14 passing through openings in these arms, and insulated from it by an insulating bushing 15. The arms are insulated and spaced from each other by. insulating washers 13 with other insulating and spacing washers 11 at the outer sides thereof. There is also preferably provided a metal switch arm cap 18 of substantially U- shape embracing these elements and clamped thereto by the screw 14. passing through the clamp. This clamp is of substantially U-shape with side arms 19 extending past the edges of the elements to prevent the switch arms 69 and I from turning on the support. outer arm Ill is a push button 80 of insulating material projecting through an opening in the side wall of the casing. It is provided with an enlarged head or flange 8i limiting movement inwardly, and a stop 82, such as a spring wire ring in a groove 83 in the button, is provided to engage the inner wall of the casing to limit outward movement. By pressing inwardly on the outer end of this button the contacts H are engaged to close the circuit through the coils 64 and oscillate the tables 32. As soon as pressure on this button is released the resilient arm will separate the contacts II to open the circuit.

The tables 32 are provided with flat surfaces 84 against which the bevels 33 of the blade engage during the sharpening operation and these surfaces are provided with shallow recesses or pockets 85 which contain a grinding compound. This may be a paste including a very fine abrasive, such for example as rouge or emery. With this arrangement by passing a finger over these table surfaces a small amount of the grinding compound is carried from the recesses to the surfaces of the table and rubbed against the blade as the tables reciprocate back and forth in a direction transversely of the edge of the blade, as indicated by the arrow 86, Fig. 1. The first action is a honing action due to the abrasive, but as the abrasive is rubbed off the surface 84 it is clear so the next or final action is a lapping operation which gives a very fine shaving edge.

In operation after the blade is clamped in the holder 2!, 22 and the tables started reciprocating by closing the switch H, the operator by manipulating the handle 7 blade laterally until it rests on one of the tables 32, and he can move this blade longitudinally back and forth along this table by sliding the shaft [9 back and forth in its bearings l1 and I8 as indicated by the dotted lines 81, Fig. 3, and 88, Fig. 6. This will provide for uniform action and sharpening of the entire length of the blade by swinging the shaft in the opposite revolution to bring the bevel on the opposite side of the blade against the top of the table on the other side of the shaft, and the blade sharpened in the same manner by sliding the shaft back and forth. The normal'operation would be for the operator after passing the finger over the surfaces of the two tables to bring a small amount of the grinding compound on to the surfaces thereof and after mounting the blade in the holder, to swing the blade back and forth between the two tables while sliding it longitudinally on the tables to alternately operate on opposite sides of the blade until the desired sharpening has been effected. This sharpening is very rapid and requires only a very short time. As the blade holder is loosely mounted on the shaft l3 it can rock sufficiently to allow the blade to find itself and assume its proper position on the tables so that the entire Carried by the or knob 20 turns the provided with a flat at 20a to engage the spring.

The tables 32 are reciprocated by the action of

cores

53 and 54 on the armatures 40. These cores are magnetized by the A. C. current in the coil 64, and it will be noted there is a magnet or core on the opposite sides of each armature. As the armature is always slightly displaced when at rest nearer to one or the other of these magnets it is displaced in favor of one magnet. When the circuit is closed through the coil the armature will be attracted to this magnet during onehalf of the A. C. cycle. As said cycle comes to zero current the armature will tend to take a central position between the magnets due to the resilient action of the spring supports 36, but due to its momentum it will overswing toward the other pole or magnet to which it will be attracted by the magnetic flux in the magnet caused by the other half of the cycle. This gives a greater amplitude to the armatures and releases power because the attractions of the armatureare on both sides of the armature alternately. It will thus be seen that the armature moves in synchronism with the frequency of the applied current, that the current is zero when the armature is in the central or intermediate position and that the current is at a maximum, and therefore produces maximum attraction on the armature, when the armature is well out of the field of one magnet and well in the field of the other. With this arrangement the armatures and the attached elements, that is the tables 32, are reciprocated at sufficient 'magnitude for the sharpening operation and in synchronism with the frequency of the applied A. C. current. As the armatures practically never come to rest at the exact central position between the two magnets the device is Self starting as soon as the circuit is closed through the coil 64. If it should happen that the armature comes to rest on the exact intermediate position any slight jar due to handling will cause it to move slightly to one side so that it would start to vibrate immediately, or the other armature being off the intermediate position would start vibrating and start the first armature.

It will be seen from Fig. 1 that as the two pairs of spring supporting elements 36 are clamped together attheir lower ends, or that is, are tightly clamped to the same support, they are mounted in tuning fork arrangement so that the two armatures vibrate in synchronism and in opposite directions. In other words they both move toward the central magnets at the same time and toward the outer magnets at the same time so. that they neutralize each other to reduce vibration to a minimum and there is practically no noise. This is the preferred arrangement but I am not restricted to this arrangement but could mount both tables on a single armature. As the two spring supports 36 are in substantially parallel or rectangular arrangement the armatures and the tables are always maintained in the same relative positions and they reciprocate in a substantially straight line.

It is desirable to have a certain mass in the table, armature and block to get a certain stroke. There is a full stroke over and back each cycle of the A. C. current. With the construction shown there is about one-eighth of an inch movement on each side of the center position or about one quarter inch stroke, but this can be varied by adjusting the stop members 50, or by making them of different lengths. In the present case the opening 52 in these members is elongated so they can be adjusted up and down after loosening bolt 42. Their position determines the amplitude or width of movement of the armatures and the tables 32. They Should be set so that when the tables are at their innermost position the edge of the blade will just pass over the rounded outer edge 32a of the table. Otherwise the stroke would be inaccurately centered and if the blade did not ride over the table edge the surface of the table would be worn down forming a ridge or shoulder against which the cutting edge of the blade would be forced and ruined. These adjustable stops 5!) permit regulation of the amplitude of vibration of the tables either together or in relation to one another without in any way changing their respective heights. This is much better than an abutment would be as the operation is quiet, and the adjustment non-changing during operation.

Another feature which tends to reduce vibration and noise is that the ends of the armature are slotted or recessed as indicated at We. This causes a sort of braking action, because when the armature approaches and before it reaches the end of its movement, a reduced portion "b at each end of this armature passes over the outer poles or legs 51 or I. so that maximum pull or attraction of these poles is reached before the armature reaches the end of its movement, and as the resistance of the spring supports 36 is increasing it causes a slowing up or retarding of the armature movement. In other words before the armature reaches the end of its movement it is retarded as maximum flux density or saturation in the reduced end portions of the armature, and therefore maximum attraction of the outer leg of the core, is reached before the armature comes to the end of its movement, and the increasing resistance of the spring supports 35 causes a slowing up or retarding of the armature movement.

In Fig. 13 is shown a slightly modified arrangement in which the armatures 40 and their spring supports 36 are located between the

center legs

55, 56 and

outer legs

51, 58 of the cores, instead of between the cores as shown in Fig. 12 and the other figures of the drawings. The operation would be the same in this latter arrangement, the single coil 64 being around the central legs 55-46 of the cores the same as in the other form, and the lower ends of springs 38 being secured to a common support 85.

It will be evident with the electrical operating device disclosed there are no rotating parts and no make and break device functioning during its operation. The device is therefore quiet in operation, vibration is reduced to a minimum, and it will operate indefinitely without attention.

Having thus set forth the nature of my invention. what I claim is:

1. In combination, a reciprocable armature, means for supporting the armature comprising a pair of spaced upright spring arms rigidly mounted at their lower ends on a support, magnetic poles on opposite sides of the armature comprising separate magnetic circuits, windings for mag netizing the poles to reciprocate the armature, a limiting element extending upright between the arms from the support, said element being of less height than the arms and spaced therefrom to limit the amplitude of movement of the armature, and means for connecting the windings to a source of alternating current.

2. In combination, a pair of armatures mounted to reciprocate toward and from each other, magnetic poles on opposite sides of each armature and comprising different magnetic circuits, a support for each armature including a spring arm rigidly connected to a support and tending to move its armature to an intermediate position between the adjacent poles, alternating current windings for magnetizing the poles to shift the armatures against the action of their respective arms to reciprocate the armatures alternately toward and from their respective poles so that they pass alternately from one magnetic circuit to another, and means for connecting the windings continuously with a source of alternating current supply during operation 50 that the armstures are reciprocated in synchronism with the frequency of said alternating current.

3. In combination, a reciprocable armature, means for mounting the armature including a pair of spaced spring arms mounted on a rigid support, magnetic poles on opposite sides of the armature, a spacing and limiting element extending from the support between the arms toward the armature spaced from the arms and terminating short of the armature to limit the amplitude of movement of the armature, windings for magnetizing the poles to cooperate with said arms to reciprocate the armature alternately toward and from the respective poles, and means for connecting the windings to a source of alternating current.

4. In combination, a reciprocable armature, magnetic cores having poles on opposite sides of the ends of the armature and comprising different magnetic circuits, a support for the armature including a spring arm tending to move the armature to an intermediate position between the poles, windings for magnetizing the poles to shift the armature against the action of said arm to reciprocate the armature alternately toward and from the respective poles, and said armature being provided with slots at the ends extending transversely the direction of movement to assist in retarding the movement of the armature at the extremes of its movement.

5. In combination, a pair of spaced reciprocating armatures, magnetic poles between the armatures and at the opposite side of each armature, the-poles between the armatures being in a separate magnetic circuit from the magnetic circuits of the poles on the opposite sides of the armatures, resilient means for positioning the armatures between their respective poles, alternating current windings for magnetizing the poles to shift each armaturealternateiy from one magnetic circuit to another, and means for continuously connecting the windings to a source of alternating current during operation. to magnetize the poles to reciprocate the armatures in Synchronism with the frequency of said alternating current.

6. In combination, a reciprocable armature, a plurality of substantially parallel magnetic core elements spaced laterally from each other and each comprising three poles spaced from each other and arranged adjacent the armature with the poles of'one element on one side and the poles of the other element on the other side of the armature, resilient means'tending to position the armature intermediate the poles of the respective elements, a single alternating current coil wound about the center poles of both elements, and means for connecting the winding through a continuously closed circuit to a source of, alternating current during operation, the resilient means being tuned to substantially the frequency of the current supply.

'I. In combination, a pair of armatures mounted to reciprocate toward and from each other, a plurality of groups of magnetic pole members one on each of the opposite sides of each armature and means for mounting and laterally spacing said groups so that they comprise different magnetic circuits, a support for each armature, resilient means tending to move each armature to an intermediate position between the adjacent poles, an alternating current winding wound about similar pole members of each of said roups for magnetizing the poles to shift the armatures against the action of their respective resilient means to reciprocate the armatures alternately toward and from their respective poles so that they pass alternately from one magnetic circuit to another, and means for connecting the winding continuously with a source of alternating current supply during operation so that the armatures are reciprocated in synchronism with the frequency of said alternating current, the resilient means being tuned to substantially the frequency of the current supply.

8. In combination, a. reciprocable armature, means for supporting the armature comprising a spring arm rigidly mounted at one end on a support, a plurality of magnetic elements spaced from each other and positioned one on each of the opposite sides of the armature and each having a plurality of spaced legs forming poles located adjacent the armature, an alternating current winding wound on a leg of both of said elements to magnetize the" poles to cooperate with the spring arm to reciprocate the armature alternately toward and from the poles of the respective elements, and means for connecting the windings through a continuously closed circuit to a source of alternating current during operation said spring arm being tuned to substantially the frequency of the current supply.

9. In combination, a pair of reciprocating armatures, means for mounting the armatures comprising upright spring arms rigidly connected to a common support at their lower ends, a plurality of magnetic members each having a plurality of spaced magnetic legs providing poles on each of the opposite sides of the armatures and located adjacent the armatures, means for laterally spacing andmagnetically separating said members so that the poles on one side of an armature comprise a different magnetic circuit from those on the other side, an alternating current winding wound about similar legs of each of said members magnetizing said poles to reciprocate the armatures toward and from each other so that they pass alternately from one magnetic circuit to another, and means for connecting the windings through a continuously closed circuit to a source of alternating current during operationso that the armatures are reciprocated in synchronism with the impressed frequency of the alternating current, said spring arm being tuned to substantially the frequency of the current supply.

10. In combination, a reciprocable armature, a

plurality of metallic magnetic circuits, each circuit comprising a plurality of spaced legs forming poles on each of the opposite sides of and located adjacent the armature with the poles on one side located in a different magnetic ci'r cuit from those on the other side, means for mounting said members in laterally spaced relation and magnetically separating them so as to form separate magnetic circuits, resilient means for positioning said armature between the poles of the respective magnetic circuits, a winding wound on similar legs of both magnetic circuits for magnetizing the poles of both circuits to shift the armature alternately from one magnetic circuit to the other, and means for connecting the winding through a continuously closed circuit to a source of alternating current during operation, said resilient means being tuned to substantially the frequency of the current sup- P y- 11. In combination, a plurality of magnetic elements forming separate magnetic circuits each including a plurality of spaced magnetic legs forming poles, an armature located adjacent said poles and movable alternately toward and from the poles of the respective elements, means mounting the armature positioned between the poles of the respective circuits so that as the armature moves toward the poles of one magnetic circuit it moves away from the poles of the other magnetic circuit and vice versa to pass from one magnetic circuit to the other, an element actuated by the armature, resilient means for positioning the armature in an intermediate position in its path of movement, an alternating current winding wound on similar legs of both magnetic circuits to magnetize the poles of both circuits, and means for connecting the winding through a continuously closed circuit to a source of alternating current during operation, said resilient means being tuned to substantially the frequency of the current supply.

12. In combination, a reciprocable armature, a plurality of magnetic elements spaced laterally and positioned one on each of the opposite sides of the armature and each having a plurality of legs forming poles located adjacent the armature, resilient means for positioning the armature intermediate the poles of the respective elements, an alternating current winding wound on similar legs of both of said elements to magnetiae the poles to cooperate with said resilient means to reciprocate the armature toward and from the poles of the respective elements, and means for connecting the winding through a continuously closed circuit to a source of alternating current during operation, said resilient means being tuned to substantially the frequency of the current supply.

13. A vibrating motor comprising at least two groups of magnetic members, each group having a plurality of substantially parallel extending magnetic legs, means for mounting said members in lateral and substantially parallel spaced relation and for magnetically separating said members, the legs of said members extending in the same direction forming a plurality of poles, a single coil placed about one leg of one member and extending around a similar leg of the other member, and means for energizing said coil with alternating current, an armature, means for mounting the armature for swinging motion adjacent the ends of the poles,said means being tuned to substantially the frequency of said alternating current.

termediate the two magnetic circuits. a winding wound on similar legs of both magnetic circuits for magnetizing the poles of both circuits to shift the armature alternately from one circuit to the other, and means for connecting the winding through a continuously closed circuit to a sourcc of alternating current during operation, said resilient means being tuned to substantially the frequency of the current supply.

THOMAS 'J. MURPHY. 10