US1186851A - Synchronizer. - Google Patents

Description

M. L. SEVERY.

SYNCHRONIZER.

APPLICATION FILED APR. 10. 1911.

1 1 86,85 1 Patented June 13, 1916.

2 SHEETS-SHEET I.

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Mai/M115 eve 1y M. L. SEVERY.

SYNCHRONIZER.

APPLICATION FILED APR.10, 1911.

l 1 86 85 1 Patented June 13, 1916.

2 SHEETS-SHEET 2.

N mfg/858981 N I, I Invenfir; WNW Z Ma vihlLSevery W a r710 MELVIN L. SEVERY, 01? ARLINGTON HEIGHTS, MASSACHUSETTS. V

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Specification of ltetters Patent.

Patented June 13, 1916.

Application filed April 10, 1911. Serial No. 620,002.

To all whom it may concern:

Be it known that I, MELVIN L. Snvnur, a citizen of the United States, residin at Arlington Heights, in the county of- Mi dlesex and Commonwealth of Massachusetts, have invented certain new and useful Improvements in Synchronizers, of which the following is a specification.

The object of this invention is the con-. struction of improved means for controlling with practically absolute precision the speed of driven mechanism, and particularly of the rotating, make and break devices for the production of electric pulsations adapted for the direct actuation of tuned sonorous bodies, as strings, in musical instruments.

I term this device a synchronizer for the reason that its primary purpose is to cause the pulsations of the make-and-break devices exactly to synchronize with the vibrations of the sonorous'bodies actuated thereby; for it should be realized that a string tuned to a predetermined pitch, vibrates an absolutely constant number of times per unit of time, and that to deliver electric impulses to the magnets actuating said string at the exact instants when the string is beginning its vibrational return toward such electromagnet, requires a degree of correspondence, or synchronism, between the impulse-producing means and the strings vibrations which is almost beyond belief. For: example, the vibrations of the upper treble strings of a piano are several thousand per second, and the synchronizing mechanism must not permit the pulsation producing devices to vary in speed a fractional part of one of such vibrations, for, if there is any such variation, a magnetic pull upon the string may occur just as the latter is beginning its vibrational swing away from the electromagnet instead of toward it; with the result that the actuation of the string will be weak, irregular, and worthless for all musical purposes.

In a mechanism so delicate as that employed in such electrically actuated musical instruments, all mechanical jolts and jars occurring from whatever cause must be reduced to a negligible minimum. One sperial cause for such jolts orjerks in mechanisms heretofore devised exists by reason of the means by which the energy of the driving means is communicated to the driven mechanism, it being physically impossible to eradicate this stuttering effect where the driving means has tangible, mechanical contact with the driven mechanism. The object of this invention is the effectmg of means for such'transmission of power which shall not be mechanical,that is, in which the transmitting means shall not employ a rigid drive or a mechanical friction, but rather a fluid one, such as that of a liquid, a gas or even some less ponderable factor as electricity.

In practice I find it preferable to employ an impositive electrical drive or means of transmission, that is to say, .one in which motion is transmitted from the driving to the driven member through the agency of an electromagnet or magnets carried by one of said members, acting upon the other of said members. In the specific embodiment here illustrated this is effected by providing one of said members with an annulus or with a disk arranged to travel between the the poles or within the field of attraction of a magnet or magnets. This annulus or disk may be made of copper or of magnetic material. When the disk or the annulus is made of copper and arranged to travel between the poles of the electromagnet, a reaction is set up between the two, due presumably to the cutting of magnetic lines of force or to eddy currents, and resulting in what is commonly designated eddy current drag. If the disk or the annulus be of magnetic material such as nickel or iron, there is a similar dragging of the driven by the driving member lncident to what maybe termed magnetic attraction and, apparently, due to magnetic lag in the disk or the annulus, tending to keep the center of the induced field retarded or behind that of the wound magnet core. Whether there be eddy currents in such case is not certainly known, but this is immaterial in any event, for it is definitely known that whether the disk or the annulus be of copper and pass between the magnet poles, or of a magnetic metal and travel within the magnetic field, motion will be transmitted from the driving to the driven member without any positive or physical contact between them. Where the disk or the annulus is of copper, the motion of the driven member will always be slower than that of the driving member, and this is practically if not absolutely true where the disk or the annulus is of magnetic metal.

Referring to the drawings forming part of this s ecification, Figure is a lan view, partly in section, of the simplest orm of the invention. Fig. 2 is a similar view of a formof the invention wherein additional controlling devices are employed. Fig. 3 is a face view of the variable resistance control. Fig. 4 is a sectional view of another form of certain parts of the invention.

As shown in Fig. 1, the electric motor 1 has mounted upon its shaft a disk or Wheel 2 carrying an annulus 3 ofcopper or other suitable material. While I prefer copper, since it is a non-magnetic substance, yet magnetic metals as nickel or iron may also be used. In exact alinement with the shaft of said motor is a second shaft 4 provided with a fly-.wheel5 upon which are located any desired number of electromagnets, but preferably two, are adapted to receive said annulus between them. When said electromagnets 6 and 7' are ,energized, the reaction, due probably to eddy currents set up in the annulus, where the latter is non-magnetic, 'or to the magnetic attraction where the annulus is magnetic, transmits more or less of the motion of the annulus to said electrom'agnets, and, through the latter, to the fly-wheel and other parts of the driven mechanism. It is of course evident that instead of an annulus as shown, said part 3 may be a disk, with the electromagnets suitably arranged to receive ihe same between thelr poles, asshown in 11 each case the annulus or the disk, whether ofmagnetic or of non-magnetic substance, constitutes in effect an armature,

moving as it does, through the field, owing to the relative or differential rotation of such annulus or disk and field.

It is obvious that a part directly geared to or otherwise ositively connected with the. driven mem r must have the same speed, or speed ratio, as the immediately driven member, hence the expression can ried by and revolving with the driven member used in certain ofthe claims following this description, is intended to apply to and include, interchangeably, such directly and indirectly driven member, by either of which the resistance varying means, hereinafter described, may be carried.

To lessen the magnetic energy of the electromagnets 6, 7, and so reduce the reactive grip or vary the per cent. of slippage between the driving mechanism and the driven mechanism whenever the latter tends to increase its speed above the predetermined. rate, the fly-wheel 5 is provided with devices by means of which more or less of the current is cut out from said electro-magnets the instant the predetermined speed is reached; the same including a centrifugal finger 8 and contact .9. v

the poles of each of which clicks.

The finger 8 is very light, and being resilient will, at anything below such predetermined speed, hold its contact-making end slightly away from or out ofactual contact with the contact '9. Being thus very light and also resilient, its action is exceedingly sensitive or delicate.

It will be noted that in the embodiment shown, the finger '8 travels in a vertical plane or path; hence with the contact 9 outside thecentrifugally-movable finger 8, gravity will tend to move said finger away from the companion contact 9 when said contacts are above the axis of shaft 4, and to move it toward contact 9 when below said axis. This force, though minute, contributes to the exceeding delicacy of action of the light spring contact 8, and insures a sharp and clean variation in resistance, evidenced in Operation by a very rapid succession of light So, too, when a relay is employed, a full or clear break is indicated, since the relay must either work or fail to work. .As a matter of fact, the relay is found to work very rapidly,many times a second,- which presumably it could not do in the absence of a clear or complete break.

It is obviously immaterial whetherv the finger 8 operate to weaken the coil or coils of the magnets as soon as the predetermined speed is reached, or to strengthen said coils as soon as the speed falls below such predetermined point. Hence contact finger 8 may be arranged as here shown and described, or to rest against the associated contact nor mally, and until a predetermined speed is reached sufficient to effect separation of the contacts through centrifugal action, and through such separation to shunt out a relatively low resistance path to the coil or coils of the energizing magnet or magnets.- In other words, I deem a mere reversal of the plan illustrated, the equivalent thereof, and regard it as comprehended within my invention and disclosure. Both embodiments have been used by me with highly satisfactory results.

When the driving mechanism is starting and when it isrunning at less than the desired speed, the electromagnets 6, 7 are energized by current fromthe source 12, the

circuit comprising the wire 13, bearing 14, fly-wheel 5 and electromagnet 6 which has one terminal grounded thereon, and thence through the wire 15 to the electromagnet 7, and back through the wire 16, a part of which is located within and out through an o ening'to the collar 17 which is insulated rom said shaft, and then through the brush 19, wires 20, 21, contacts 22, 23 and wires 24, 25 and part of 26 back to said source. Inasmuch as current is at the same time flowing from said source through the wire 27 to the relay electromagnet 29, the return being through the wire the hollow shaft 4,

30, resistance 31 and wire 26 back to said source, said contacts 22, 23 are held in engagement as above implied, and the circuit thereby maintained so long as the driven mechanism is below its predetermined speed.

The instant such predetermined speed is reached, however, the spring contact finger 8 carried by the fiy-wheel 5 is caused by centrifugal energy to engage the contact 9, and a circuit is thereby closed, which circuit consists of the wire 13 coming from the source 12, bearing 14, fly-wheel 5, said contacts 8, 9, the wire 10, insulated collar 11, brush 33, wire 34, resistance 31 and wire 26 back to said source. This circuit contains considerably less resistance than the one including the wire 27, electromagnet 29, wire 30, resistance 31 and wire 26, and consequently the larger part ofthe current will thereby be shuntedaround said electromagnet 29 and the latter receive insufiicient current to hold the contact finger 22 in touch with the sta tionary contact 23. Said'contacts 22, 23 being thus separated by the action of the spring attached to the swinging armature, only that amount of current permitted by the resistance 35 will be delivered to the elec-' tromagnets 6, 7, so that there will be weakened magnetic fields and a reduced impelling force between the annulus3 and flywheel 5, thereby lessening the driving moment and hence the speed imparted to said fiy-wheel. As soon as this speed slightly reduces, the contacts 8, 9, separate, the relay magnet 29 closes its contacts, increased ourrent is delivered to the magnets 6, 7, and again the driven mechanism is speeded up.

The speed of the fiy-wheel 5 being usually very high and its mass considerable, it is not easily affected by any slight influences. For this reason, the increments and decrements in the clutching power of the magnetic system'are exceedingly slight, and so very delicate in character that they are practically incapable of detection. The continued action of the finger 8 upon the contact 9 is moreover so frequent, being afiected not only by speed changes infinitesimal in amount, but also by gravitational influences where the device is run in a vertical plane, ,and this frequency of contact varying the I magnetic moment of the magnets 6, 7 which require a definite length of current-flow in order to rise to their full strength, that the whole system apparently strikes a balance in which the magnets 6, 7 are automatically varied in strength very closely in accord with the necessary power required to produce synchronism in the driven mechanism; thus still further assisting in rendering the speed changes slight in the extreme.

It is evident that in the construction shown in Fig. 1, the electromagnets 6 and 7 will,

when raised to a given magnetic moment for a definite length of time, exert a 4 thus leaving relative propelling force upon the fly-wheel 5 which will vary as the speed of the motorv varies. This variation, due to the fact of the mass of said fiy-wheel and the further fact that neither the magnetic moment of the magnets 6 and 7 nor the duration of the contact between the finger 8 and contact 9 is of fixed value, is ordinarily negligible. There are cases, however, in which it is essential or at least highly important, that the change in speed of the motor be rendered absolutely negligible in effect upon the driven mechanism. This is especially true where the variation, if any, is cumulative, as for instance in orientation of scientific instruments, ratus, and the like, it being understood of course that this invention is intended for use in connection with various classes of apparatus requiring the maintenance of synchronism or timing of one moving part or object with or in relation to another. Multiplex telegraphy, aerial telegraphy, ringing systems, and various others will readily suggest themselves as falling within such field as well as musical apparatus of the class here indicated. In order to render changes in speed of the motor thus negligible, I employ the devices shown in Fig. 2, Where the real driving force is transmitted through a spring the action of which is made absolutely constant upon the driven mechanism by the use of a fusee arrangement, during the free movement of such spring. In order that such spring may in operation be kept within its free limits, I provide a changeable resistance factor adapted so to vary the magnetic strength of the magnets 6, 7 that the motor and its disk and annulus shall, throughout all motor speed changes occurring in practice, urge the fiy-wheel with just the amount of energy necessary to keep the said spring approximately at its center of free motion. Under these conditions, said spring will drive the driven mechanism with perfectly constant urgency; and this urgency I prefer to make somewhat greater than ordinarily necessary to drive the driven mechanism at its desired speed.

To prevent the driven mechanism from racing, I employ a magnetic damping arrangement which is adjusted so as very nearly to consume the surplusage of power, a relatively small amount of damping workto be done by an intermittent electromagnet and its associated circuitopening and circuit-closing system.

In the last-named form of my synchonizer, the fly-wheel shaft 4 has loosely mounted thereon a fusee 40 having wound thereon the cord 41 connected with the free end of above-referred to spring 42 which is of crescent form and has its other end fixed to a post 43 projecting from a disk 44 rigidly mounted on said shaft. Carried by said as telescopes, with recording appafusee is a variable resistance member comprising resistance connected at different points thereof to insulated contacts 46 (Fig. 3), one end of the resistance being connected through an annular contact 47, brush 49 and wire 50 to the wire 51 joined to both the electromagnets 6 and 7. The latter have their other terminals grounded to the fly-wheel 5 and hence in circuit with one pole of the current-source, through the bearing 14 and wire 13. In touch with said contacts 46 is a brush 52 supported by a post 53 projecting from said disk 44; such brush being wired to the insulated sleeve 54 having a brush 55 in contact therewith which is connected through wires 56, 57 to the other pole of said current source 12. In this manner, any partial turnof the fusee cuts difi'erent sections of resistance into the circuits to the electromagnets 6 and 7; and by having the driven mechanism here represented as a circuit-interrupting rotor, 36, geared to said fusee through the gears 59, 58, any change in the speed relation subsisting between the speeds of the fly-wheel and shaft, and the driven mechanism, will react upon the spring 42, partially to turn the fusee and so vary the resistance. By suitably arranging said spring,- fusee and resistance, any relative increase in speed on the part of said fiy-wheel and rigidly connected parts is made to cut more resistance into the circuits of the electromagnets 6, 7, and any decrease in relative speed to cut out resistance. As in the construction first described, such variations in resistance in said magnets circuits cause them respectively to decrease and increase in magnetic energy, and correspondingly to receive less or greater moments of rotation from the annulus 3.

To apply suitable drags to the driven mechanism one of which is preferably constant and the other intermittent, said driven mechanism 36 (see Fig. 2) has geared there to a drum 60 carrying an annulus 61 of copper or other suitable metal, rotating between the poles of the constant but adjustable electromagnet 62 which takes its energizing current from the source 12 through the wires 57, 63 and 64 to itself, and thence through the wire 65 back to said source. In addition to said electromagnet 62, said annulus rotates between the poles of an intermittently energized electromagnet 66.

The last-named electromagnet takes its current from said source through the wires 57, 63, 67 and 69, stationary contact 70, contact finger 71, and wire 72 to itself, and thence through the wire 73, bearing 74 and connecting members of the machinery, bearing 14 and wire 13 back to said source. When said contacts are put in touch, the electromagnet 66 is energized and an added drag put upon the annulus and connected parts. For thus actuating the contact finger 71, its

connected armature is located in the field of a relay electromagnet 75 which is adapted to receive current whenever the driven mechanism 36 reaches or attempts to pass the predetermined speed. To do this, said magnet is connected with one pole of the source 12 through wires 57, 63 and 67, and with the other pole through the wire 13, bearing 14, framework and other parts of the machine to the wheel 60, centrifugal contact finger 76 contact 77, wire 80, sleeve 81, brush 82 and wire 83.

While I prefer to have the electromagnets 6 and 7 carried by the driven mechanism in order that their weight may, on the one hand be utilized to increase the inertia of the -wheel and other driven mechanism, and also, on the other hand, in order to free as much .as possible the rapidly revolving motor-armature from weight upon its bearings, yet I do not restrict myself to such arrangement, since it is evident that the motor 1 may be connected with said fly-wheel, and the copper member 3 connected with the driven mechanism 36, as shown in Fig. 4.

It will of course be understood that a prime motor of as nearly constant s eed as practicable will be employed, and t at the present invention is designed so to control the driving relation between the driving element on the one hand and the driven element on the other, as that despite slight variations in the-speed of the driving element (which are almost inevitable), the driven element and the associated timed pulsation-producing devices, or equivalent devices, shall be driven at a constant speed or a speed so near absolute constancy that the infinitesimal error, if any, shall be inappreciable to the human eye and ear, and negligible.

It will be observed that it is necessary to the perfect operation. of this apparatus, that the prime mover be capable of afiording power and speedsufiicient to drive the driven element up to its full required speed, and

preferably somewhat beyond such speed;

that until such speed is reached the supply of current to the electromagnet or magnets of the driving couplin is constant and practically unvarying; that the instant the driven element passes or tends to pass such predetermined speed, the current supplied to the electromagnet o-r magnets issharply speed of the driven element is rendered absolutely'.'constant, or so nearly constant that the variation or error is inappre'ciable and ne ligible.

n the embodiment here illustrated that element of the coupling carried by the motor constitutes the driving element of the coupling, and the co-acting element of the driven mechanism constitutes the driven element, and these terms will for convenience and brevity be used in the claims. As indicated, the coupling operates without any physical or positive connection or contact between the driving and the driven elements, for which reason I term it an impositive driving connection or coupling. As set forth in the opening part of this specification, such impositive connection may be established with a fluid or a liquid as the power-transmitting medium, and these as well as the electrical means are to be understood as comprehended within this invention in its broadest aspects. It is characteristic of couplings of this class that in certain of their embodiments the speed of the driven element is always less than that of the driving element, there being what is commonly termed a slip. In other Words, there is a differential motion produced, and under actual working conditions such slip, greater or less in degree, is always present in such couplings. By controlling this slip the speed of the driven element may be varied and controlled with the utmost nicety and precision, and without producing any ar, shock or concussion. The increments and decrements of speed may be so infinitesimal as to be incapable of detection by the eye or ear, yet are sufficient to bring into play the controlling means, and thus to maintain the requisite constancy of motion essential to perfect synchronism between the actuated body, as a tuned string or the like, and a pulsation-producing rotor controlling the periods of attraction of the electromagnet by which such string is vibrated. In the drawing 36 indicates a rotor composed-"of a series of'disks, carried by a common drum or support, each disk havingalternate conducting and non-conducting segments or sections, through which the circuit of an electromagnet 84. is alternately opened and closed at such point. Suitable keys as those of a piano keyboard, complete the circuit as required for the vibration of a given string, indicated as 85, in the manner well-known in the art, and shown in Patent No. 814,878 granted to M. L. Severy and G. B. Sinclair, March 13, 1906, among many.

In application Serial No. 619,633, filed in my name on the 7th day of April, 1911, I have shown and described apparatus embodying certain features of that here illustrated and described, but employing a friction, instead of an impositive, drive or coupling for transmitting motion from the rime motor to the ultimate driven parts. lhe present application is designed to cover and claim a structure having an impositive coupling or driving connection, as hereinbefore defined. Such features as are common to the two applications but are not specifically claimed herein, are reserved for said application Serial No. 619,633.

In certain other co-pending applications are shown, described and claimed, in some instances broadly and'in others more specifically, devices which are designed primarily for maintaining synchronism of movement of a plurality of bodies. All matters set forth and claimed in co-pending applications filed in the joint names of myself and George B. Sinclair, or in the name of either of us, and not definitely expressed in the claims hereof, are expressly saved and re served for one or another of said co-pending applications in which such matters are claimed or intended to be claimed. Among these co-pending applications may be noted body carried by one of said elements; one

or more electromagnets carried by the other element, said body being adapted to be rotated freely between the oles of said electromagnets; means for de ivering current to said electromagnets; and automatic means for diminishing the supply of current to said magnets when the speed of one of said elements reaches a predetermined rate.

2. In combination with a body requiring movement at a predetermined and precise rate per unit of time, an electromagnet for effecting such movement; means including a source of electric energy, a current pulsator, and a circuit in which said electromagnet is included, for producing pulsations in the magnet; a prime mover for imparting motion to the current pulsator; an impositive coupling interposed between said prime mover and pulsator, and comprising a driving and a driven element; and means carried by the driven element, and serving through variations in the speed thereof to determine the sli of the coupling or the relative speeds of its driving and driven elements.

3. In combination with a body requiring vibration at a predetermined and precise rate per unit of time, electromagnetic means for effecting such vibration; means includin a source of electric energy, a current 'pu sator, and a circuit in which said electrofor imparting motion to the current pul-.

'sator; an impositive coupling interposed connected with said mechanism,

between said prime mover and pulsator, and

comprising a driving and a driven element; and means carried by the driven element and serving through variations in the speed thereof to determine the driving moment of the coupling, substantially as set forth. 4. In combination with a tuned sonorous body and with an electromagnet for imparting vibration thereto, a source of electric energy; a circuit connecting said source and said eiectromagnet; a current pulsator included in said circuit, for producing pulsati'ons therein; a iIlOtOI' for movingsaid ulsator; an impositive coupling interposed between said motor and said pulsator, comprising a driving and a driven element;-and means carried by the driven element, adapted to control and vary the slip or differ'erlti'al movement of the drivmg and driven elements through and in accordance with variations in the speed of the driven element; whereby the current pulsator is caused to maintain a predetermined and ur'fif'orm speed, and thus to synchronize the current pulsations with the predetermined rate of vibration of said sonorous body.

5. In combination with a driving element and with a driven element, one provided with an electromagnet and the other with a disk or annulus movable within the field of said magnet; a control device carried by the driven element, and adapted to vary the intensity of the magnetic field in inverse relation to changes of speed of said driven element. a

6. In combination with a driving element and with a driven element, one provided with an electromagnet and the other with a disk or annulus movable within the field of said magnet; a control device carried b the driven element and ada ted throng the attainment of a predetermined speed by the driven element to weaken the intensit' of the magnetic field, and through the fal of the speed of the driven element below the predetermined point, to str'ieingthen the intensity of the magnetic fie 7. In combination with a driving element and a driven element, one provided with an electromagnet and the other with a metallic body movable through the field of said magnet; a circuit for said magnet including a source of electric energy; a resistance associated with said electric circuit; and means adapted to be brought into action throu h the attainment of a predetermined speed by the driven element, and serving when such speed is reached to introduce said resistance into the magnet circuit.

8. In combination with adriving element and a driven element, one provided with electromagnetic mechanism and the other with a member adapted to be impositivel of a centri ugally-actuated spring carried by the driven element, and adapted to vary the strength of the impositive connection in inverse relation to changes of speed of said driven element.

9. In combination with a driving element and an element to be driven, an electromagnet carried by one of said elements; a metallic body carried by the other of said elements and arranged to cut the field of said magnet; means for delivering-current to said electromagnet; and means for diminishing such current when the driven element attains a predetermined speed, such means includin a source of current and circuit, and a centrif ugally-actuated spring finger controlling said circuit.

10. In combination with a driving element and an element to be driven, an electromagnet carried by one of said elements; a metallic body carried by the other of said elements and arranged to cut the field of said electromagnet; a source of current and a circuit for said electromagnet; resistance included in said circuit; a centrifugal circuit-closer mov able by said driven element; a circuit including said source of current and the contacts of said centrifugal circuit-closer; a resistance in the last-mentioned circuit; contacts in a shunt about the second-named resistance; a relay electromagnet controlling the last-named contacts; a'connection between said relay electromagnet and a point in the first-named circuit, adapted to bring the resistance of said last-named circuit between such point and the nearest pole of said source; and a connection between said relay electromagnet and the opposite pole of said source.

11. In combination with a "motor and a body to be rotated thereby, an impositive coupling for transmitting motion from the motor to said body, comprising a driving element directly connected with the motor and a driven element having a shaft mounted in bearings; electromagnetic means carried by the coupling elements, and serving to cause the driven element to follow the rotation of the driving element; a source of energy for said electromagnetic means; a variable resistance device incircuit with said source of energy, for determining the intensity of the magnetic field; a gear wheel loosely encircling the shaft of the driven element of the coupling, provided with a fusw and carrying said variable resistance device; a spring carried by the shaft of the driven coupling-element; a flexible band connected with said spring, wound upon, and attached at one end to said fusee; and a gear wheel carried by the body to be rotated and meshin with the loosely mounted gear on the sha t of the driven couplingelement; whereby motion is transmitted from the driven coupling-element through the spring and fusee to the body to be rotated, and the resistance device is turned to different angular positions with relation to its contact brush, to vary the intensity of the magnetic field in accordance with the differential movement of said driven element and its loosely encircling gear.

12. In combination with a motor and with a body to be rotated, an impositive coupling for transmitting motion from the motor to said body; and a magnetic damping device to prevent racing of the rotated body, comprising a drum connected and rotatin with said body, an electromagnet, a metal ic annulus extending into the field of the electromagnet, one of said parts, the electro magnet or the annulus, being carried by said drum and the other fixed against movement, a circuit for said electromagnet, and a centrifugal circuit-closer carried by the drum, and serving when said drum attains a predetermined speed to close the magnet circuit and energize the magnet, thereby causing a reaction between the magnet and the annulus serving to dampen or retard the movement of the drum and of the rotated body.

13. A synchronizer comprising a driving mechanism, a driven mechanism; an impositive coupling between the two whereby the former rotates the latter; means operated by the speed of the driven mechanism for supplying thereto power sufficient to drive it beyond a predetermined speed; means operated by the speed of the driven mechanism for decreasing the power supplied thereto to a point insufficient to drive it to said predetermined speed, the last-named means operating instantly said predetermined speed is exceeded, and the first-named means operzfitilng instantly said predetermined speed a ls.

14. A synchronizer comprising a driving mechanism, a driven mechanism; an impositive coupling between the two whereby the former rotates the latter; and means for forcing said driven mechanism continually and rapidly, by an almost infinitesimal margin, to cross and recross a predetermined speed irrespective of any speed variations in said driving mechanism.

15. A synchronizer comprising, in combination, a driving mechanism; a driven mechanism; an impositive coupling between the two whereby the former rotates the latter; a centrifugally-actuated spring carried by the driven mechanism and bearing a contact; a second contact with which the first co-acts to complete an electirc circuit; and means whereby upon the completion of said circuit the impositive coupling is supplied with one degree of power, and upon the opening of said circuit it is supplied with another and materially different degree of power.

16. A mechanism for producing a substantially constant speed drive from a driv-' ing member subject to speed variation, which comprises a rotary field member and a rotary armature member associated therewith, said field and armature members being adapted to exert a rotary driving effect one upon the other, one being connected to said driving mechanism and the other being the driven member; a centrifugally-operated resistance-varying means carried by and revolving with the driven member; a source of electric current; and an electric circuit including said field member, said source of current, and said resistance-varying mechanism.

17. A mechanism for producing a substantially constant speed drive from a driving member subject to speed variations, which comprises a rotary field member and a rotary armature member associated therewith, said field and armature members being adapted to exert a rotary driving effect one upon the other, one being connected to said driving mechanism and the other being the driven member; a speed controlled resistance-varying means carried by and revolving with the driven member; a source of electric current; and an electric circuit including said field member, said source of current, and said resistance-varying mechanism.

In testimony that I claim the foregoing invention, I have hereunto set my hand this 6th day of April, 1911.

MELVIN L. SEVERY.

Witnesses:

GEORGE F. WALES, A. B. UPHAM.

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