US448894A - Electric meter - Google Patents

Description

2 Sheets-Sheet l.

(No Model.)

E. TELOIVISOIY.y ELECTRIC METER.

No. 448,894. Patented Mar. 24, 1891.

PIM l, i

im" A A INVENTEIR.

(No Model.) 2 Sheets- Sheet 2.

E. THOMSON.

ELECTRIC METER.

No. 448,894. Patented Mar. 24, 1891.

@MMM-Tf UNTTED STATES PATENT OEEi-CE.

ELlllU THOMSON, OF S\YA\ll)SCO'l"`, MASSACHUSETTS, ASSIGNOR 'lO THE 'llllOhlSON-HOUSON ElilC'lRlC COMPANY, OF CONNECTICUT.

ELECTRiC METER.

SPECEFICATON forming part of Letters Patent No. 448,894, dated March 24, 1891.

Application tiled September 26, 1890. Serial No. 366,204. (No model.)

To all 'zo/tom, z'f may concern.-

Be it known that I, ELTHU Teensex, aeitizen of the L'nited States, and a. resident of Swampscott, in the county of Essex and State of Massacliusetts,liave invented certain new and useful Electric Meters, of which the following is a specilication.

My invention relates to electric meters for use on either continuous or alternating current circuits; and it consists in certain details of construction and combinations which in the main are more particularly applicable to meters wherein an electric motor is employed andthe consumption is indicated or registered by the speed of suoli motor.

One part of my invention relates to the construction of the commuiatorof the motor, the objectbeing to insu re reliability and regularity of action of the meter by eliminating as far as possible the element of friction and the deterioration of the com inutator-eontacts or change of any character therein which would tend to change the resistance or make the action of the apparatus imperfect.

Another feature of my invention consists in the introduction in that circuit of the motor wherein a constant strength of current should be maintained of an. artificial resistance external to the motor and made large in proportion to the resistance of the uiotor itself. This feature of my invention is of particular value when the armature and the field-magnet of the motor are traversed by separate currents, and the armature is made to carry the current of constant strength, the vfield being excited by current varying' with the consumption. The particular results accomplish'ed by this feature ot' my invention will be referred to more in detailhereinafter.

Myinvention consists,also,inotherfeaturcs, to be more particularly hereinafter described, and then specified in the claims.

The meter to which l have shown the iniprovements constituting my present invention applied is like that described in my prior application, tiled August 26, 1889, Serial No. 321,988, and comprises, generally speaking, a motor traversed by the current for propelling or rotating a shaft or other mechanism which operates a register and a retarder of the movement of the motor cousistin g, of a closed conductor in moving relation to a magnetic field, or vice versa.

ln the drawings I have illustrated the inc ter as connected upinthe manner preferable when it is to be employed for measuring the consumption of energy on a constant potential circuit, although the mechanical features and constructions hereinafter described are applicable to electric motors generally, and the resistance applied inthe circuit of the meter might be employed when the meter is connected up in other ways or upon other circuits.

In the accompanyingdrawings, Figure lisa perspective or isometrical projection of a meter having the general elements of construction described in my prior application before referred to, with modifications in the details constituting my present invention. Figs. 2, 3, l, and 6 illustrate parts of the commutating devices. Fig. 7 illustrates in vertical cross-section the bearings of the armatureshaft of the motor. Fig. 8 is a plan of the retarder mechanism inodilicd in accordance with niy present invention. Fig. 9 shows in perspective the armature structure carrying the armaturecoils and constructed in the manner preferred when the meter is employed for metering alternating currents. Fig. lO is a diagram illustrating one way of connecting up the circuits of the meter and the application to the meter of an artincial resistance in accordance with my invention.

Referring to Fig. l, S is the shaft which carries the armature A, constructed as hereinafter more particularly described, which armature revolves in a field produced bythe action of two coils C C', thelatter of which is here indicated in dotted lines. The movements of the armature are registered or counted by a register R geared to such armature-shaft. The armature inightbeof the ring type,though it is preferred to make it, as indicated, with a set of coils wound somewhat after the fashion of a Siemens armature, and connected to a commutator K, constructed in the manner to be presently described. The retarder D, carried by such shaft, consists of a disk of copper, which revolves past the polesof several permanent magnets M, mounted on the base B of the machine.

One of the features of my present invention Ais the arrangement of magnets M in such Way that the poles on the same side of they disk D shall alternate in polarity, as indicated in Fig. S-that is to say, the magnets are reversed in position as to their opposite poles, so that amagnet which hasanorth pole above and a south pole below the disk shall beA followed, proceedingr in the direction of revolution of the disk, by one Whose north and south poles are respectively below and above said disk.

For the purpose of varying the retarding efects produced by the traverse of the disk, plate, or conductor D with relation to the poles of the magnet, I mount or support one or the other element of the device so that it may be adjusted with relation to the otherin a plane parallel to the plane of movement-land insuch Way as to change the speed of the traverseof. one part past the. other, thereby changingrthe starengthof the induced or Foucault; currents set upand varying the` resistance to movement. Such adjustment may be; conveniently attained by pivoting one of such magnets, as indicated in 8, so. that by'swinging it on itsv pivot the. distance of its poles from: thecenter of the disk will be changed. Bythis adj ustment a calibration of the rotations of the motor-armature may bereadily effected.

B.- isan extension from the base B for supporting thev artificial resistance-coil placed in the; circuit ofthe motor,`- as hereinafter deT scribed, Whilel P is the` upper pivot for the shaft; S; andv J J are side standards from whichthe pivot and the register mechanism are supported.v

In order to provide for transportation of the; apparatus without injury, I apply to the low-er end of the shaft S lan adjustable lifting and` supporting device, such as indicated at P2, Fig. 7Whereby the shaft may be lifted and: supported off its pivot. The lower pivot of the shaft S- isindicated at P3, Fig. 7, while thetlift-er referred to, is indicated at P2, and is mounted as a` nut upon a screw-standard carrying thepivot-bearing, so. that by screwing upv they lifter P2' it may be brought into engagement with a cup-shaped: extension. F, carried at the lower end of, the shafts, below the, disk D. When supported by the lifter-screwPz, engaging with such cup-shaped` extensionthe pivotal bearings of the shaft are protected from injury, and lateral move-l mentof the shaft andpartsconnected therewith during transportation is prevented'.

lOne. of the gr eat obstacles to success in the operation of electric meters having electric motors-.with a comm utator has been the considerable friction which has heretofore ex-r isted-Yat the commutator, as well. asthe varia-V tions in the friction and the development of imperfection in the commutator and variationsof resistance thereatthrough the action off, thecurrent and minute sparks onthe coxn mutatorsurfaces.

for the bearing or contact surfaces of the revolving segments of the commutator and the brushes bearing on the same. To reduce the initial friction to the smallest possible point, the colnmu-tator-cylinder should be made of as small a diameter as is practicable, the contact-brushes beingmade to bear thereon 'with any extremely light pressure. This extremely light pressure becomespossible bythe use of pure silver for the commutator, since the velectric currents may be passed throughl it without burning and Without deterioration;

I'have found by experiment that silver used l in'` this manner does not corrode or form a i'lm ofV none-.conducting oxide inY the air. Hence the eect of slight sparking at the commutator is small, there being in substance no oxidizingeffect, or, rather, the effect-ofv the heat produced being tored-uce the oxide back to the pure silver. Owing tothe fact that silver is an excellent conductor of heat, any heat developed is rapidly carried off from the contacts. and dissipa-ted. A further advantage isthatthe metal is readily obtained in a pure state and is the best known conductor of electricity.

It is'not sufficient for thev purposes of my invention to make onepart only of thecommutator of silver and to use another metal for the other portion. Platinum I` find to be unsuitableY for the purposes, owing to the fact that theL contacts are spoiled by the deposition of platinum black when sparks. are formed', the substance being a non-conductor to almost the extent of platin um oxides. For the same reason I have found it impossible to makea meter which shall be practicable when copper is employed for the contacts, owing to\ the fact that copper oxidizes and does not remain bright, especially when there is a slight sparking. The difficulty from oxidation might be gotten ridi of by einploying gold; but such material is not suitf able, irst, because of its expense; secondly, because it is a poor conductor, and, thirdly, because it is more difcult to work in a pure state. Platinum, though easily worked, is a poor conductor, and is found to be unsuitable for the reasons above stated. Be-

sides introducing anelectrical resistance, Which isv undesirable', the platinum dust producedl when platinum is employed for the commutator causes an increased mechanical f friction of the surfaces.. This difliculty I find tobeentirely absent Whensilver is employed, the coeiiicientof friction of silverbeing prac- IOC IIO`

tieally the same during motion as at startiiw. Other experiments made by me on the use of copper with carbon, or of carbon for both parts of the commutator, gave results that were not satisfactory, the meters when subjected to trial eitherbreaking down after running for a greater or less length of time or failing utterly to yield uniform results, and it was clearlydemonstrated that it was futile to work with the substances ordinarily employed for commutators of electric motors, and that only by the employment of silver could good results and uniform work be secured. I find that it is also very desirable to construct the commutator K of the motor of just as small diameter as possible. ln fact, as near the diameter of the shaft or spindle upon which it is carried as it is possible to make it and maintain the insulation of the commutator-segments from the shaft. By resorting to this feature of construction l avoid a difficulty which has been heretofore niet with-to wit, the element of friction, which element, if too large, would render the meter altogether inoperative on small loads.

The details of the commutator are illustrated more fully in Figs. 2 to 6, inclusive. To construct such acommutator I preferably proceed as follows: T, Fig. 2, is a silver tube, which may be a drawn tube, and which is taken and divided by longitudinal slits, as indicated in Fig. 3, which stop short of the ends of the tube, as indicated, and divide the same into the required number of segments for the commutator. Such a tube is taken and forced upon the armature-shaft S, Fig. et, a thin layer of insulation (shown in black in the figure in exaggerated thickness) beinginterposed between the tube and the shaft. The segments are now bound down upon the shaft by means of two encircling bands, indicated in Fig. 5, which are of insulating material, or of conducting material lined with insulating material. The segments are by this means fastened in place, after which the ends of the cylinder are cut on?, leaving a series of segments insulated from one another and held together by rings on an insulating-support encircling the shaft closely. The ends of the segments or strips to which the armaturewircs are to be connected may be bent away from the shaft, as indicated in Fig. 5. lt is obviously not necessary to leave both ends of the tube unslit, since the proper relative position of the segments prior to the binding' of them upon the shaft will be preserved in a measure if one end only were left unslit. It is best, however, to leave both ends unslit, since the segments are thereby kept more rigidly in their proper relative position during the construction of the commutator.

The brushes indicated in Fig. S may consist of pieces of spring metal shed at the end with little plates of silver, or they may bemade entirely of silver, as is obvious. They should be constructed to bear upon the commutator with an extremely light pressure.

lf the meter is to be used for alternating and direct current measure interchangeably, it is obvious that the construction must be special to the case, and for this purpose I wind wire only without iron cores to be magnetized, thereby leaving simply an air-field t0 be produced by the field-coils and to be acted upon by the armature-currents in producing rotation.

To receive the coils of the armature, l construct a hollow frame, (exhibited in Fig. 9 and consisting of two insulated disks or disks of insulating material Q Q,) placed at a dis* tance apart on the shaft S and having polygonal outlines, preferably for ease of winding the armature-coils. The projecting pieces at the angles of the polygonal surfaces separate the coils during the winding operations and can afterward be removed or cut down. These disks are preferably separated by a few insulating-pillars, which, however, might be made of brass or other nonfmagnetic metal, and which are indicated at V V. The outside of this structure is now covered by winding coils, as shown, one coil alone being seen in the figure, the other coils making an angle with the coil shown, and wound in the manner of a Siemens armature, and all of the coils being connect-ed into closed circuit. Of course it is necessary that each face be occupied by two coils in such a winding, or at least that the spaces be in pairs, so as to complete the closed circuit, as is well known. l

TOO

thus secure a hollowframe, which enables the coils to be mounted and ventilated, and which gives slight spaces between the coils, so that no effects of increased temperature by the current iowing is felt, and the coils are made of very line wire compactly placed, so as to get the greatest electrical work out of them, taking into consideration the absence of any iron core in their interior. The armature-coils A, then, and the lield-coils themselves produce what may be called air-magnets, reacting upon each other to give rotation to the structure.

In Fig. lO the meter described is shown applied to a circuit. a b, on which electric lamps L li or other devices are operated in parallel, such circuit being one which supplies a current of approximately constant potential to said devices. The held-exciting coils C C of the motor are included in the main electric circuit with the translating devices, as shown, so that the strength of the field will vary with the consumption of energy on the circuit. The electric armature A is in a branch of high resistance across the mains, as indicated, so that it will, when normal and proper action of the meter takes place, be traversed by current constant in amount. This relative arrangement of the parts in the circuit is claimed in my prior application before referred to. W is an artificial resistance in the circuit of the armature, but external thereto, and made high in amount, so as to limit the current and avoid the necessity for IIO winding the armature of extremely-fine Wire to stand considerable poten-tial. By making this resistance very high in proportion to the armature-resistance, a practically-con stant current in such armature under conditions of change of speed is attained, owing to the fact that the variations of resista-nce4 and counter electro-motive force in` the armature itself will be so small in proportion toI the total resistance as to be practically negli-- gibl'e. The high resistance WV will therefore also-have ani-mportant function in practically abolishingv any variations in the action of the motor arising from any change of resistance at the commutator-con'tacts, and will for thisl and the reason above noted add greatly to; the regularity offaction of tl're` motorl y Y In the casek of a meter operated by alter; nating electric currents this resistance, which is external to the armature, is wound so as to and a commu tator for said motor, having both' its moving and stationary conducting-sur# 'faces made of pure'silver, as and for the purpose described.

2. In an electricl meter, an electric motor having a commutator the brushes andfsegments of which are bothmade of pure silver, as and? for the purpose described.

3.' In an electric meter, an electric motor having its commutator constructed'of as small diameter asY practicable and from someA non- 'oxidizing material,in combination with com'- mutator-brushes of non-oxidizable material bearing thereon with light pressure, as and for the purpose described.

4. The combination, with the armature shaft orspindle S, of thevcommutator-cylinder consisting of a nnmber'ot' strips of. thin' sheet metal. fastened directly upon: a thin layer of insulating material encircling the shaft and having their free ends bent outwardly for attachment of electricconductors. f 5. The herein-described improvement in constructing commutators, consisting in slit- .operatedA by ,alternating currentsof a noninductive'artificialv resistance placed in that lportion of the meter-circuits wherein a con-- l stant current is maintained andmade to form Vthe larger part of the resistance of said circuit.

ting'a tube longitudinally by slits extendingl a suiiicient distance tocomplete the separate commutator-segments, leaving one or bothV ends of the tube unslit, thereby completely forming the desired number of commutatorsegments, binding the slit portion of thetube at or near both ends down upon the shaft over an interposedl layer of insulatingmate rial, and' then cutting'od the unslit endj or ends.

6. The herein-described improvement in constructing commutators of small diameter,

consisting in taking a tube of greater length vthan necessary to form the complete commutator, dividing the same by longitudinal slits suicient in length to complete commutatorsegments of thel desired Width in the direc-V a` retarder consisting of a closed conductor inl movin g'rel'ation toa magnet adj ustable,as described; so as'to change the distance ofthe polesof such' magnet from the center of the movable disk.

8; The combination, in an electric meter, of a retarding mechanism consistingot' a disk or plateV of copper and" a'l magnet in moving relation to one another, one of` said' parts being adjustablev in a plane parallelI with the other for the' purpose of changing the relative speedof traverse of the one part with relation tothe other, and thereby varyingv the retarding eifec't.

9. The combination, with theretarding disk orrplate D, of a' pivoted magnet M, adapted to swing in a plane parallel' with the plane of the disk.

10. In an electric 1neter the combination, with a motor anda registering mechanism, of av retarding device consisting of a plate or conductor and a series of magnets the poles of which embrace the platev and alternate in polarity, as and for the purpose described.

l1". In an elect-ric meter, amotor-armature structu-re consisting of two disks of insulating material, having polygonal outline and fasten'ed together by pillars of non-magnetic material, and electric coils wound over such disks withventilating-spaces between the coils, as

and forthe purpose described.

12. In an electric meter, the combination, with an electricmotor and a register for countlng' the movementsthereof, of an artificial resi'stance external to the motor and placed in the circuit of such. motor wherein a constant curren-t is to be maintained, such resistance being the larger part of the total resistance l of such motor-circuit.

13. 'llhe'combinatiom with an electric meter 14. The combination, with an electric motor operated; by alternating currents, of a. regisg ter forcounting. the movements 0f 'said motor, and av non-inductive articial resistance eX-V `Iternal to'the'motor and placed in the meter 'circuit' including'the armature and commuf IOO IIO

tator, such artiileial resistance bein` made large iu proportion to the resistance of the normal resistance of the armature and coinmutator.

l5. The Combination, in an eleetrie meter, ot an electric motor having its eld traversed byeurrent varying,` with the consumption and an armature for such motor placed in a constant-current eircuit,in combination with an artificial resistance placed in the armaturecireuit external thereto.

1G. The combination, substantially as described, of an electric-motor field-coil, an electric-motor armature-coil provided with a coininutator and placed in an alternatingeurrent eireuit, ineluding a non-induetive resistance external to the armature and e01ninutato1,as and for `the purpose described.

17. In an electric meter for measuring alternating electric currents, the combination,

with that part of the inotor which is included 'in a consta-nt alternating-current circuit, of a non-ind uctive resistance external to such part ot the motor and niade large in amount in proportion thereto. Y

1S. In an electric meter, the combination, with the armature-shaft, of a cup-shaped ex tension at or near the lower end thereof and a screw-support P3, consisting of a nut upon a screw-standard which Carries the pivot-bearing,` for the shaft, as and for the purpose described.

Signed at Lynn, in the county of Essex and State ot' Massachusetts, this 23d day of September, A. D. lSQO.

ELIHU THOMSON.

Witnesses:

JOHN W. GIBBONEY, AXEL EKsTRoM.

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