Патент USA US2110418код для вставки
Màrch .8, 1938. S. S. GREEN 2,110,418 ELECTR IC METER Filed March 26, 1936 .'5 Sheets-Sheet l Mmh s, 1938. s, s. GREEN ELECTRIC METER mmm lènguggpnm 2,110,418 -Marçh 8, 1938. 2,110,418 S. S. GREEN ELECTRIC METER Filed March 26, 1956 QNS 3 Sheets-Sheet 3 "l @P ’Patented Mar. 8, 1938 ' 2,110,418 _UNITED STATES PATENT OFFICE 2,110,418 _ Enno'rmo METER „Stanley S. Green, La Fayette, Ind., assignor to Duncan Electric Manufacturing Company, La Fayette, Ind., a corporation of Illinois Appiication March ze', 193s, serial No. 70,951 " 17 Claims. (Cl. ITI-'5264) \ In the past, one common way of producing ad This invention relates to velectric watthour meters and has been illustrated as being embodied jacent fields of opposed polarity and adequate in a two-element meter. In most of its aspects strength was to provide'a large magnet having it is equally suitable for single element meters, both of its poles above the disc, with an arma Y5 and in fact one of the important advantagesof ture below the disc opposite said poles, the ilux 5 the illustrated form ,is the readiness with which y passing downwardly from one pole into the arma it may be converted to a single element meter. . ture and upwardly from the armature to the other For many years efforts have been made to pro duce metersy so that they would be'not only more 10 satisfactorylin operation but also more econom ical in manufacture and more economical in use , from the standpoint of taking up the minimum pole. This was a fairly economical manner of attaining this result, but it had several draw backs which caused 'it to be discontinued com mercially. L > Due to the fact that the magnets, in order to be large enough to have adequate strength, ex amount of Wall space. In my copending »appli cation Serial No. 33,116, I disclosed a polyphase tended close to the sides of the meter case, it was impossible to mount several meters side by side meter Which takes up only the Wall space hereto fore required by a single phase meter, while at in closely spaced relationship without introduc ing what was called an “adjacency error”, be the same time conforming to present high stand ards in electrical performance. That application' cause large portions of the damping magnet of covers the «interference-proof disc for polyphase one meter were so close to those of another meter that there would be appreciable flux leakage be 20 meters, and a novel arrangement of the major tween the two magnets. According to the pres parts which is -more eñlcient and satisfactory, especially from the manufacturing standpoint and ent invention this is overcome by using a small in requiring‘the minimum of Wall- space. The and properly positioned magnet made of a high present application is intended to cover various coercive magnetic material instead of a large magnet `of a metal conventionally used in watt 25 improvements, most of which are made possible hour meters, such conventional metals having by using this latter feature, and involve the use 'of very high coercive permanent magnet steels. relatively low coercive characteristics; This Although the metals themselves are not new, their small but high-coercive magnet is placed at a use in kilowatt-hour meters is new -and has var 30A ious advantages which are peculiar to electric meters. - ' l The type and arrangement of damping mag position suiilcientlyf removed from the periphery of the meter case, as shown at 32 in Fig. 1, so 30 that there is no appreciable meter adjacency error; At the same time the efficiency obtained nets is an importantfeature of this invention, by having two opposed fields from one magnet but to make its significance clear, it is necessary .is retained by having both poles on one side of the disc, as seen in Fig. 6. This is in contrast to 35 to briefly explain the action of damping magnets in an electric'meter. A damping magnet sets up another prior practice in which'the adjacency a magnetic ñeld for opposing the rotation of the error due to the use of one large magnet was disc to make its speed proportional to the power avoided by using two smaller magnets, one for vconsumptionmeasured by the meter. _ The disc ' 40 does not touch the> magnets, and in fact rotates With as little friction as possible. It is.common practice in damping magnet arrangements to provide` two adjacent fields of opposite polarity through `which the,- meter disc rotates. The 45 ldamping effect depends upon the speed of change of vilux in a given portion of the disc as it passes vthrough these ñelds. This speed of change de pends, in turn, not only on the total magnetic. ñux in these fields, but- also on their concentra tion and proximity. The most important parts of the two ñelds are those parte which are ad jacent to one another, since the stronger these two parts are, the more rapid will be the change yof iiux’through a given portion of the disc as it 55 from one to the other. ‘ . each of the two opposed iields,v each magnet straddling the disc, having one pole above the disc and the other below, and the two magnets being alined and positioned almost end to end. > Thisconstruction, however, was more expensive, partly because of the difllculty of accurately mounting the two magnets as well as the -extracost of fabricating two magnets, instead of one. Such a construction is alsoespecially unsatis factory when economy of space about the disc is necessary. Nevertheless this isthe practice which has been universally followed in recent years in all meters ofthehighest quality. ` The large single magnet of the discontinued prior art also failed to make the best use of the available magnetic flux, since it failed to -con - centrate the iiux from the two poles in the zones i 2 2,110,418 adjacent one another as thoroughly as this should be done. A According to the present invention the meter case, showing the meter element in side elevation. fluxes are very concentrated in these most ef fective zones, as seen in Fig. 6. _ meter adjusting armature. Fig. 5 is a horizontal sectional view through the One methodof accomplishing this is shaping the magnet so that only the faces of the poles are adjacent to the disc, the magnet extending upwardly from these poles instead oi’ substantially parallel to the disc as did the large single magnets ofthe prior art mentioned. Another feature which contributes same; and Fig. 6 is .a side view of a magnet comprising one feature of this invention, with an armature 'and a »fragment of a disc adjacent thereto, and the direction of flux indicated. Fig. 7 is a chart showing magnetic character istics of metals. Fig. 8 is a fragmentary plan view of a preferred form of meter disc. toward the same end of concentration of iiux is shaping the magnet so that its cross section ad jacent its poles is less than its cross section else 15 ` Fig. 4 is a Vertical sectional view through the where, especially at its central portion (the upper half of the magnete). It is obvious that except for leakage, the ñux of the/entire magnet is thus concentrated in the relatively small pole pieces. With the large prior art magnet mentioned, Although this invention may' take` numerous. forms, only one has been chosen for illustration. In this -form the meter includes any suitable meter base II and cover I2 as well as the meter mechanism mounted on said base and enclosed by said cover. 'I'he meter mechanism includes 20 one factor which detracted from concentration 20 of iiux in the most effective zones was the use of a round amature, this armature being round an inner driving unit having a laminated core I3 which is mounted on the base in any suitable ‘ so that it could be turned on a screw to be screwed toward or away from the meter disc and the manner, a frame I4 mounted on the _core I3 of the magnet beyond ,the disc for the purpose of adjust Y inner driving unit, an outer driving unit having 25 ment. According to the present invention the a laminated core I6 mounted on said frame Il, armature is made generally rectangular corre a meter~ disc 2| rotatably carried by the frame, spending in shape to the desired zone of con- ' the 'damping magnets 32 and their armatures centration, so that it need not have any parts . 41 and 48 forming an important part ofA this drawing the magnetism away from the zone of invention, and a register indicated diagram 30 concentration. For the purpose of adjustment, matically at 23. The driving units may be identi 30 the armature may be divided, and one part of it cal with those shown in my copending applica- . moved parallel to the disc relative to the other tion Serial No. 48,713, although the laminated part. The two parts of the armature are thus coresv I3 are preferably made»- up of a thinner `partially separated to impede the flow of flux stack of laminations than was illustrated in that application. Each driving unit includes a voltage 35 35 through the armature. Another drawback to the magnets heretofore coil 24 and a current coil 26. In the preferred used in meters is their requirementfor a. sub form the laminations are secured together partly stantial amount of temperature compensation, by spacer rivets 68 which also secure attachment which compensation takes the form of divert 40 ing part of the iiux of the magnet from its useful channels. According to the present invention the lugs 18 and 'I9 to the cores. 40 Arrangement of parts An important feature of the preferred forml magnets are made of a type of metal which -re quires relatively little temperature compensation of this «invention is the arrangement of the driv ing units and permanent magnets 32 as shown, with the driving units at opposite sides of the 45 disc and the magnets 32 between the driving units and at opposite sides of the disc axis from one another, with these damping magnets having both poles adjacent one face of the disc (by which is meant that both poles> are above or both poles and therefore can use a relatively greater amount ' 45 of their flux for the damping eiïect. An additional objection to the magnets of the ‘prior art is that to prevent their being per manently weakened by stray ñelds, as a ñeld from the current magnet if there should be- a short 50 circuit, it was necessary to protect the permanent` magnet from said field either by considerable are below the disc) and their armatures on the distance or by a suitable shield. Either form of opposite face of the disc and alined with their protection involved expense and inconvenience. poles. This arrangement 0f parts permits se According to the present invention the magnets . curing adequate damping torque for a two element meter in a minimum of space, without 55 55 are, of such nature that this protection is not any material adjacency error, and at exception ally low cost. 'I'his feature of arrangement is A necessary, a high-coercive material being used. The objects of. the invention are not only t0 covered in applicantfs copending application pre viously mentioned, and it should be borne in overcome the difficulties previously mentioned, ybut also 'to provide a more economical and satis 60 factory meter construction aside from these mind that many of the remaining features may be used without this feature. particular considerations. One speciñc object, for example, is to provide an improved form of Meter frame meter adjustment which, though very economical, is exceedingly delicate and accurate and capable 'I'he desirable'arrangement with damping mag-~ nets between drivingmagnets is attained largely 65 of utilizing substantially all of the available flux. Other ‘objects and .advantages of my invention will be apparent from the following description, taken with the drawings, in which: , Fig. 1 is a front sectional view of the form of 70 meter chosen for illustration, >taken approxi mately through the line I-I of Fig. V3, with a portion of the case broken away. g . f‘ ` Fig. 2 is aperspective view of the meter frame shown in‘Figl 75 1. ' ‘ ‘ ~ i - Fig. 3 is a vertical sectional view through the \ , through the use of the frame I4 which is secured to the spacer rivets 68 and 14 of core I3 in any suitable manner. 'I'he frame I4 is constructed as shown clearly in Fig. 2 and is cast of a non magnetic.v material such as aluminum. 'It in 70 cludes a pair of inclined seats 3| against which the magnets 32 are secured. There may desirably be a raised boss 33 on each of these seats 3|, through which is drilled a hole suitably threaded for a screw -which holds the magnet in place. 75 2,110,418 A washer‘36 of non-magnetic material may de sirably be provided between the head of the screw andthe magnet. The seats 3I are extended up wardly and integrally connected to mounting lug 38 and to brackets 4I. The brackets 4I sup port the upper disc bearing as is described below. Extending downwardly from -the seat 3| is an integral extension in the form of a loop 43, which , loop extends around and under the meter disc' 10 44 and includes at its bottom portion seats 46 on which are mounted the armatures 41 and 48 as explained below. The central portion of the loop 43 forms a support for the lower bearing holder 5 I. This bearing holder is not new with the pres 15 ent invention andi therefore need not be described . 3 . the segment 6I and> also in the segment 48 but, due to the differential pitch, it screws to the right inthe segment-6I faster than in the segment 48, and thus draws the segment 48 towards the seg ment 6I. _ _ Likewise when the screw 62 is turned in the `opposite direction, it screws to the- left in seg ment 6I faster than in segment 48 and hence it separates the segment 48 from the segment 6I. This movement is limited, however, b_y engage 10 ment of threads 64 with the segment .48 since the threads 64 will not ñt the threads in the seg ment 48 which engage the threads 63. It isvthus seen that the length of the unthreaded or re duced portion 65 between the threads 63 and 64 may be utilized together with the difference in pitch to determine the maximum amount of sepa-I ration of the two armature portions 48 and 6I. It should be observed that the diiîerential` er 5I preferably has a jewel bearing on which y thread arangement may be designed to give any the meter disc 44 rotates. The upper end of the desired degree of delicacy of adjustment, even shaft 52 of the meter disc is kept in the vertical though both of the threads may be fairly large position in a substantially frictionless manner ' and strong. If the pitch of one thread differs by an upper bearing pin which is held in a bear from that of the other by only a hundredth or a in detail. It passes through the bearing support portion 49 and screws into the same, having an annular shoulder which seats against the bot tom of the support portion 49. The bearing hold ing holder 54. v The preferred construction of . thousandth of an inch per revolution, the arma 25 this bearing holder is adequately illustrated in tures will be separated by only the corresponding my said copending application Serial No. .48,713. y amounts. Expressing this differently and giving This bearing support 54 screws into a plate 56 a typical preferred example, if the thread 64 has which is shown as secured to the brackets 4I as a pitch of twenty-four turns to an inch, and the thread 63 has a pitch of thirty-two turns to an 30 30 by suitable screws 51, though the plate may be inch, then in one revolution oi' the screw it will 4an integral part of the frame I4. Y move one twenty-fourth of an'inch in the block \ Damping magnet armatures 6I, but it will/move one thirty-second of an inch lThe armature 41 is preferably a rectangular _in the other block 48. The net movement of the 35 35 block of metal. of high magnetic permeability block 48 will therefore be one twenty-fourth of an such as commercially pure iron. Its upper face >inch minus one thirty-second of an inch, or, in is preferably directly opposite the faces of the other words, one ninety-sixth of an'inch. poles of the adjacent permanent magnet 32 and vOperation of adjustable armature coextensive with the outer edges of the poles. 'I-'he armature 41 is secured in place'in any de The operation and effect oi the adjustable ar sirablemanner as by screws 56 extending through maturegare quite simple. As the two portions are the~ seat 46 and screwing into the armature 41.v separated,- the reluctance ofthe armature flux It is evident that the disc 44 rotates between the path is increased and therefore less iiux passes magnet 32 andthe armature 41. ` ' ’ from themagnet through the disc to the arma The armature 48 may be 'the same as the arma vture and back through the disc to the magnet ture 41 but it is preferredA that it be in two rela than with the armature portions closer together. tively movable parts to provide for adjustment of It follows that the damping effect is reduced. It the meter, unless other adjustment of this type is is possible that part of the reduction in damping provided. It should be understood that it is com effect is vdue to shifting the position of the fluxy mon practice to adjust' meters by varying the as,well as to decreasing the amount of the' flux, amount of damping ñux which passes through inasmuch as when the portion 48 is moved away the meter disc. In the present instance this 'is . from the portion 6I itis no longer directlyoppo accomplished by shifting that part of the arma- ‘ site the face of the pole of the magnet 32 and ture to which the numeral 48 is applied toward therefore the iiux` may no longer be concentrated or away from the other part which is designated at its most 'effective position. by the number 6I. The portion 6I may be se Mounting of frame cured` to its seat 46 inthe same manner as the armature 4'_I is secured to the other seat 46. The The frame ' I4 is secured at its top to the core I3 portion 48 may slide on the seat 46 and is ad of one driving unit by means of a bracket 66 justable towards and away from the armature which may be secured to the 1ug`38 by a screw portion 6I by means of a screw 62 engaging both 6.1 and to spacer rivet 6_6, by a screw 63. The y portions of the armature.- Various screw are bracket 66 may desirably have a leg 1I extendingrangements’may be used such as having the screw beyond the spacer rivetv 68 and against the core threaded in one member and simply pivoted in 'I3 for further rigidity. The frame I4 is further the other member `without being longitudinally secured to the core I3 by screws 12 which may` movable therein. To permit more delicate ad '_ desirably pass through bosses 13 formed on the justment, however, the ent shown' in frame, and screw into spacer rivets 14 on the Figs, 4 and 5 is preferred. ‘ According to this construction the screw 6_2 70 has two differential or independent threads 63 and 64 formed thereon, both-of which are right hand threads, though both may be left hand threads. The thread 64 has slißhtly greater pitch than the thread 63. It follows »that when the 75 screwisturnedclockwisaitscrewstotherightin laminated core structure I3. ~ y ' 45 50 55 60 - Mounting of front driving unit The front driving unit is secured to the frame in a manner _similar to the mounting of the in ner unit, or rather it is secured to-a link 15 se cured to post 16 which is formed on the lug 38 75 4 2,110,418 -of frame It, and to _the posts Tl formed on the looped portion of the frame i6. -The driving unit -I6 is provided with an attachment lug 'I8 through which a screw is passed and screwed into the bracket 1E. It is likewise provided with out- . metals are able to force much more flux through the meter disc than chrome steel or others of its class, if each were made up in a magnet of a given size. ' Although various general characteristics of standing attachment lugs ‘I9` through which these metals have been known almost asV long as screws may be passed and screwed into posts 11. the metals themselves, the metals have certain It will be observed that the two core structures` advantages peculiar to kilowatt-hour meters not i3 and I6 are identical, even as to the lugs pro ' known before the present invention. This is vided for mounting. As a mattei' of fact, spacer partly because all the higher coercive materials rivets 0l on the front core i6, similar to the spacer are much greater in cost on a weight basis than rivets it, may be used for mounting the register 23 and name plate 82, both of which are secured the commonly used chrome variety. Radical changes in mode of application to the watthour to mounting plate 83 which is secured directly to meter mechanism have been necessary to make 15 said spacer rivets. .their use commercially possible, since high-co ercive steel used along the lines of recent meter Damping ‘magnets designs would have had much more total coercive For many years a chrome steel of relatively low force than could be used effectively, and hence coercive force has been used in meter magnets much higher cost than would have been justified. 20 because the meter designs were not such as to The primary change has been the use of a new 2 take advantage of the high-coercive steels which - magnet of short total length compared with the have been available in thelast few years. ` One gap length. With the chrome steel the ratio of typical such steel contains 8.50 percent chro useful magnet length to gap length has usually mium, .90 carbon, .33 manganese, .101 phosphor exceeded 50 to 1. In the present preferred form 25 us, .015 sulphur, .29 silicon, .20 nickel, and the of the invention I have found a ratio of even as rest iron. ` l low as ten to one to be sufficient. - This has been \ Some of the permanent> magnet steels which . the basis ~for the selection of a small length mag have become available commercially having much net oi' general horse-shoe shape but of heavy higher coercive force values, are the high cobalt ‘ cross-section in which the flux is forced through 30 steels and the nickel aluminum steels. Qne form the disc gap twice, thus, in reality, doubling the of the latter group which vhas become available actual length of gap as far as the flux path is commercially is known by the trade designation concerned. Such extra gap length is the means of “Alnico” because in addition >to about 20% by which the high coercive force of the steel is nickel and about 12% aluminum it also contains utilized. It may be noted at this pointv that if 35 about 5% cobalt, the rest being iron. A good the armature is fixed with respect to the magnet, survey of the iield of such available materials >to Vas is armature 41, the available coerciveforce in gether with a bibliography is contained in an ar a magnet may be more fully used, since it is not ticle by C. S. Williams in the January, 1936, issue necessary to provide an excess to take care of of Electrical Engineering and need not be further adjustment. For this reason other means of ad discussed here. Therel are numerous patents justment than varying the, armature may be pre purporting to relate to high-coercive steels, in ferred. _The departures in fundamental gap re cluding Patents Nos. 1,633,805, 1,947,274, 1,989, lations and shaping have resulted' in a damping 551, 1,968,569, 2,027,994, 2,027,995, 2,027,996,2 magnet so radically different from former watt 027,997, 2,027,998, 2,027,999, and 2,028,000. ' hour meter practiceas to introduce entirely new For reference, the following table of typical space Aand arrangement problems in its applica 45 coercive values of different» common materials is tion to the meter disc. The solution of these has included: » ï ’ resulted in a meter ofl great flexibility, light weight, low cost, and simplicity of assembly, to Coercive Aälä‘ääïœ -force in - 50 Low-coercive steel: 55 eo . oerqœds residual tlux elsewhere. i in kilcgauss The use of a smaller magnet permits the most advantageous positioning of these magnets, es ` 60 to 64 - . 36% cobalt steel _____________ _. 240 to 250 420 to 440 _ ` 9. 4 within the space above the disc rather than pro~ 10. 2 jecting outwardly beyond the disc, and thus it » Alnico ......... ____ __________ __ ' pecially in that it permits their being included o Old or usual form of chrome steel- -.._ Higlrcoerclve steels: gether with the other advantages mentioned It will be observed that the chrome steel can overcomes the'tendency to adjacency errors when two meters are located closely together. To get the best use of a given weight of metal, not be considered as in a class with the latter two the magnets are preferably shaped substantially materials, since these are characterized by having as shown in Fig. 6, in which it is seen that thev a coercive force value of at least three times that of the chrome variety that of Alnico being over six magnet, though of general horseshoe shape, is thicker at its center top portion than at its poles. times. There are, of course, steels _between those mentioned above, such as 17% cobalt steel, but The larger cross section of the magnet near the 65 this table _shows the diñerence between low and flux which crosses the gaps,'but also the leakage high coercive steels. It will be noted from thev second column that the residual flux values of the Alnico are some what lower than for the other materials but this 70 is more than made up for by the highl coercive value for the material when used in accordance with this invention because the structure, gap and shaping of the magnet in this case is such as to capitalize on or take advantage of this factor 75 .rather than to throw itv away. 'I'he- last two midpoint must carry not only the useful ldamping iiux between the poles. Thus the crossvsection near the poles need not be as great to secure op eration of the magnet at the „most efficient point of substantially uniform ñux densityfthroughout its length. Moreover, this taperinggof the-polesy has the additional advantage of causing the flux density at the poles to be as great as further back in the magnet and, as has been pointed-out, this concentration of flux density at the gap' greatly increases the damping effectiveness 'of a 7| 2,110,418 given amount of ñux, especially when the concen trated flux zones of opposite direction are closely adjacent to one another. The shape of the mag net shown would give approximately uniform flux density throughout the magnet. ’ Referring to Fig. 6, it is seen that to the left of the line A-A the flux is all downward, and to 4the right of the line A-A the flux is all upward. Thus as a given. portion of the disc 2"I lies under the pole S, the flux> will be passing downwardly 5 perature compensating clip 9| may be provided. These clips may be secured underneath the washers 36, one ,under each washer, an'd may be ‘somewhat U-shaped if desired so as to 'extend closer to the faces of the poles of the magnet, 5 thus straddling the horizontal portion of the frame Il as do‘ the magnets themselves. The washers 36 may be specially shaped, being ñat tened along their lower side so as to fit above the horizontal portion of the frame I4 and, ii' 10 desired, being recessed on their inner faces to through it, but when said portion moves to lie receive the clips- 9i. As is Well known, these _ under the pole N, the ñux will be passing upward ly through it. It is this change in the direction of temperature compensating clips may be made of flux passing through a given portion of the meter any magnetic metal having a negative tempera disc which produces the damping eiïect, and the ture coefiicient such as nickel steel. One >well 15 more rapid the change is, the greater is the damp ’ known steel widely used for this purpose con ing effect. In other'words, it is the intensity of tains 29.5% nickel and approximately 69.5% iron. » Certain important advantages of mounting the flux just to the leftA of the line A--A and just to the right of the line A-A‘ which is most impor- ' damping magnets above the disc and with arma- ` tures below, have already been discussed: ,it per- 20 tant in the damping effect. Due to leakage be tween the poles S and N, it is not possible to get mits avoiding adjacency error, makes a compact ' high concentration of flux exactly adjacent to the arrangement of parts possible, >and provides ad li?e A---A, but it is possible to concentrate the jacent opposed ñelds from a single magnet. 'I‘here flux approximately under the faces of the poles are, however, at least two other important ad vantages as comparedr to using two adjacent 25 Ul by means of the use of the armature 41. Since greater concentration of the flux close to the line magnets each having one pole above and one be »A-A‘ produces greater damping effect, it- follows low the disc. One is obtaining the desired width that by tapering the poles, the iiux is less spread of gap and the other is in the adaptability of a out and is l'therefore concentrated under the two-elementl meter to a single-element meter. poles, and hence closer to the line A-A than if- Resistance of damping magnets to magnetic disw 30 `the poles, not being tapered, extended further turbances away from the line A--A. In order to obtain a magnet having this tapered shape economically, When meters are installed under practical it is preferred to use a magnetic metal which may be cast or molded to this shape. It should be" noted that the proportions shown in Fig. 6 are approximately those of an alnico magnet which has been found to be satisfactory. The outer face conditions on the utilities’ supply lines to service customers, they are likely to be subjected to two 35 classes of magnetic disturbance. In the iirst of these, a short circuit occurs- on the load side of the magnet is tapered too much, its eñiciency rated current of the meter to ñow through the the meter (that is on the consumer’s side) which ’is shown, and is slightly'longer than the inner ‘ may cause a transient current of from one hun- i face on account of the slant of the magnet. If dred'to even one thousand or more times the 40 might be impaired on account of increased ñux leakage. p ‘ » , current `coils, (depending upon the short-circuit capacity of the supply system and the severity of The use, in accordance with this invention, of the short-circuit). In the second of these classes of magnetic disturbances, the potential circuit 45 the rectangular armatures 41 and 48 substantial ly no larger than the spread of the poles, also l of the meter is subjected to a transient over-volt contributes to the concentration of flux, since if age of very' short duration, usually- because of a the armature extended beyond the area of de sired concentration it would draw some of the flux away from this area'. As a matter of fact. it may be desirable to have the armature slightly smaller inthe direction concentric with the disc than the dimension across the pole faces of the magnet in this direction. It might also be better to have the outer opposite sides of the poles and of the armatures radialrather than parallel. From Fig. 1 it will be observed >that the mag nets 32 are slightly inclined. The chief advantage of this is thaty the average spacing between ad jacent magnets .of adjacent meters is greater, although the faces of the magnets are kept at the most effective position close` to the edges of surge caused iby lightning. "These lightning surges may be of all‘magnitudes up to a value sufficient to burn. up the meter, but the great 50 majority of surges are insufiicient to do this, and dissipate themselves by causing abnormally large transitory currents in the potential windings. When either one or a combination of the above two classes of abnormal surges occur, strong mag- ` 55 netic ñelds are set up around the meter coils and their core structuresmay become completely saturated, causing strong leakage fields. These transient fields may be of the order of hundreds or even thousands of times the normal value .of 60 the leakage fields to which the damping mag nets are subjected in usual operation. These transient fields are usually produced by alter the meter discs. As a matter of fact, it is pre nating current (and in consequence are demag ferred that the corners of the poles of the mag ' . nets extend approximately to the edge of the netizing. In prior art meters, designers have always disc so as to obtain the greatest damping torque. As previously stated, magnets made with the guarded against such fields by keeping the damp ing magnets as far away as possible from the elec preferred metal have very little temperature er tromagnet coils (usually on the diametrically op ror, since they have a relatively low temperature coeiñcient with respect to the magnetic ilux posite side of the meter disc). Even further than 70 this, they have (in. the best quality of meters) al which they produce. They do have a slight tem perature error, however, and the remaining parts ways provided some form of shield vof magnetic of the meter such as the cores I3 and I6 also , material (usually cast iron) between the electro have very slight temperature errors. To compen magnet and the permanent magnet'. Thus, prior sate for these errors and overcome them, a tem art meters have often or usually had the frame 75 6 ariane of the meter of lcast iron. The shielding eiïect has only guarded against magnetic surge elfects partially as it is practically impossible to com pletely guard against a magneto-motive-force by magnetic shield means.- (Distance between the electromagnet coils (where the disturbance origi nates) and the permanent magnets has been an Vchrome _____________________________ _'_ 33-42 Amico _______________________________ „_ 831-100 ' not function eiîectively).V It is therefore evi dent that the two most important safeguardsv of the prior art are completely absent, and a com mercially acceptable job in the reduced space 20 would be impossible except for the greatly aug mented use of a third safeguard. .This third safeguard may be more easily un derstood by reference to Fig. 7, and especially the .left hand portion thereof. Chrome steel `has usually been magnetically “aged” before its ap plication to a meter. This “ageing” has consisted 'in the application of a demagnetizing force (usually in the form of a magnetic ñeld produced 30 ~ ,40 45 50 Ui. Ul 60 In this example the'Alm‘co had not been knocked down nearly to the point Y but instead was be ing operated at a point at about Z. .ObviouslyI if it is no_t necessary to go to Y, there is some econ omy by operating at a point such as Z-" It can be shown by expert and detailed analysis that the knockdown ampere mms per unit of length are a close measure of the degreev of im munity of a given magnet to demagnetizing in iiuences such as the aforementioned surges. Therefore it can be seen »that »the Alnico mag net,--depending upon what A. C. knockdown isy deliberately given to it,'-.can be made atleast two times as resistant as magnets of the prior art while producing almost as much ilux, even in 'a closed circuit, or three or more times as re sistant while having much greater energy value. Actual tests vhave vshown that the utilization of this third and last factor, to the necessary de by an alternating current). This force has gree, is the most reliable way of guarding against usuallyI been one sufficient to bring the residual ' surges. The inventor has constructed and tested 30 flux down to approximately the point X on the ‘a meter with spacings and arrangement accord curve. It will be seen that this point is at the ing to this invention which was actually more re value of B and -I-I where the maximum energy sistant to surges than any prior art meter, not product PX is produced for the chrome steel. The withstanding the close spacing. maximum energy product of a magnet is the high- v The present invention marks the ñrst time that est product obtained by multiplying the coercive damping units and driving units have ever been force at any point on its hysteresis curvev iFig. 7) successfully used in close proximity and Without by the flux intensity at that point. At the top of shields between them of magnetic material. the curve the product is 0 because the coercive \ Material used in meter frame yf_orce is 0. At the bottom of the curve the prod 40 uct is 0 because the flux is 0. Somewhere be It has previously been mentioned that the tween there is a maximumenergy product. Of meter frame is made of aluminum. Of course course X could be brought down still further on many other non-corrosive non-magnetic metals the curve but not much further without consid of adequate strength which can be cast to shape erable sacriñce in energy product and hence in may be used as well. As has just been discussed, 45 damping eiîectiveness. \With the chrome steel the use of a high coercive material ln the damp this demagnetizingforce applied is about forty ing magnets makes possible this use of a frame flve oersteds (gilberts per centimeter). Against which does not act as a' shield for the magnets, demagnetizing forces up to but not exceeding this, although the arrangement of parts is so compact the magnet would be immune.> that shielding would be necessary otherwise. 50 'With Alnico, the demagnetization 'can be> con 'I'here are numerous advantagesl in the use of tinued without great sacrince of damping eili this type of frame which greatly enhance the ciency to the point Y where a value of about 320 value of the use of the high coercive metal which , oersteds is obtained (or over seven times the value permits the use of the frame. For the ñrst timev with chrome steel), with approximately the max it has been possible to get along without added ëö imum energy product Py. . y clamp members or the equivalent. Now itis pos Of course it may not always be necessary to go sible to secure the permanent magnets directly to the extreme of descending on the Alnico curve to the frame without increasing the flux leakage. to the point Y but if necessary it can be done. 'I'he manner ofvobtaining gap accuracy is ex 'I'he result would be a magnet immune to demag plained under _the next heading. " 60 _ netizlng forces up to approximately 320 oersteds. In this connection it should be noted that some of the available coercive force of the magnet is consumed in driving the useful or damping flux across the gap, but in general- much of it re mains to be fully available as a safeguard against demagnetizing stray ñelds. . Some examples may make this matter of age ing more clear. A chrome steel magnet in wide use (by the applicant’s company) has a devel oped length of six inches, a single gap of .100", and withstands from 200 to `250 ampere turns of alternating current demagnetizatlon (or knock doyvn, as it is commonly'called) . 75 veloped length for' the two are: i the prior art. room for the addition of magnetic shields (and 15 without greater space as well, the shield could i) .125"> each and Withstands 250 to 300 ampere turns of alternating current knockdown. The knockdown ampere turn values per in_ch of de even more important factor than the shielding of In the present invention the damping magnets are placed in- close proximity to the electro magnet coils. Moreover. the frame of the meter is'preferably of cast aluminum, and there is no 10 vention, has the same damping power, has a de veloped length of three inches, with tWo gaps of An Alnico magnet, preferred in the present in» Another advantage is the elimination of trou blesome magnetic particles which always are l likely to get into the meter with any machined parts made of a magnetic metal such as the old cast iron frames. These particles could not be removed reliably in any commercially practi cal way, and in a meter they were especialy like ly to accumulate on the poles of the magnet, thus affecting the speed of 'the disc. < - Another advantage is that the frame does not` 70 need to be painted, since it is inherently non-cor rosive. AThere has always been trouble in the past with paint chipping oil? and getting in the bearings or gap as well as leaving the frame ex posed to corrosion. yIn this connection it may be 75 2,110,418' 7 mentioned that the Alnico magnets are also rust - rather than to limit the invention to these fea tures, except- as the prior art may require. ' proof, so that paint may be omitted from- them - also. I claim: ` ’ The advantage in reduction of weight in the use of an aluminum frame 4(andinthe use of any 'ï 1. An electric Watthour meter including a con tinuously rotatable disc, a, plurality of driving units acting on said disc and having approxi frame of its skeleton nature)~ is obvious.> mately parallel core' structures adjacent diametri Obtaining desired gap width ' cally opposed peripheral portions ofthe disc, and With the magnet arrangement shown, it is not an upwardly extending damping magnet located 10 necessary to grind the gap between the poles to the desired size as when the disc must rotate through this gap. With the present construc between the cores with its pole pieces adjacent one face of the disc, and an amature adjacent the other face of the disc and alined with said tion, the desired gap width can be obtained with' adequate accuracy simply by applying the arma pole pieces,_ said magnet slanting from the disc` ‘ tures 41 and 48' and magnets before the disc is in place. A spacer gauge is placed on each arm metal having a `coercive strength higher than one inwardly,v and said- magnet being formed oi' a hundred eighty oersteds. ature and the corresponding magnet 32 is slid->`--- " 2. An electric Watthour meter mechanism in along its seat 3| until its rests on the spacer cludingh a disc mounted for continuous rotation> about a given axis,- a plurality of driving units gauge and then the screw 3l is tightened to main acting on said disc and having approximately 20 20 tain- this spacing. The gauge is then removed parallel core structures adjacent diametrically - Í`and the assembly of the meter is completed. opposed sides of the disc, a damping magnet sub- - Uonversz'on to single-element meter Another advantage of the type of magnets 25 here used, and one which is newly attained by stantially within a cylindrical _space subtended by the disc extending steeply away from the disc, and having its poles close’together and both ad 25 - the present invention is that a two-element meter l ’jacent the same face of the disc and spaced sub mechanism such as Vthe polyphase meter illus trated, may be converted to a single element me stantially equally from `said axis, and an arma ture opposite said polesv and adjacent the oppo ter simply by removing the front driving unit site face of said disc and constituting a low re 30 I6 and the lefthand one ofthe damping mag _ luctance path for causing the ñux to pass through 30 nets 32., Perhaps more important than this from ` d the disc in opposite directions in passing from one ' the lstandpoint of the user of meters, a single phase type can be changed into a polyphase meter by Aadding the front electromagnet element and one damping magnet, and of course changing pole of the magnet to the other, said damping magnet being made of a magnetic material >having a coercive strength of at least“ 180 oersteds and b‘eing in a magnetic state corresponding to 35 the connections for the outside circuit according - its having been previously magnetized and then `ly. Also, a manufacturer can make either> single subjected to a knockdown force equivalent to at . phase- or polyphase` meters from the same stock least 120 oersteds. 3. A watthour meter includinga driving unit of parts.- As a matter of practice, the disc will usually be changed, since for the polyphase meter for rotating a disc,` a suitably ysupported frame of it is preferred to use an interference proof disc non-magnetic metal. a disc mounted on said - such as that shown in Fig'. 8 having live insulated laminations, each- having ñve radial slots ex tending from the outer edge nearly to the center of the. discs. Such discs are expensive and are not necessary in single phase meters. The ad frame for continuous rotation, a damping magnet secured directly to 'said frame and having both poles adjacent one face of the disc for retarding the rotation of the disc, said frame extending around to the opposite face of the disc from said magnet, and an armature secured to said frame vantage of havingv the other parts standard for both single phase and polyphase meters is very opposite said magnet but adjacent said opposite important nevertheless. face of the disc. 50 ` l I , ‘ 4. A watthourmeter comprising a torque pro ducing electromagnet, a disc drivenby the elec Torque-balanced disc ., . lAnother novel result of the illustrated arrange ment of parts is that the forces around the disc are balanced in such a way that there is no radial pull on the disc shaft when the two driving ele ments are measuring equal power consumptions, no matter how great the torque may be. The two driving elements act on the disc as a whole 'in exactly opposite directions (one to the right 60 and one to the left), and the two damping mag nets also act in exactly opposite directions, so l_that each set of forces is balanced except as to torque. With suitable bearing design, this saves wear on the bearings of the disc, as compared to a construction in which both the damping mag tromagnet andcapable of continuous rotation, anda damping magnet for said disc, said'magnet being of general horseshoe shape with its end faces comprising pole faces both of which are ad“ 55 jacent one face of the disc and having an arma ture cooperating with said pole faces adjacent the opposite face of the disc, said magnet being made of a material having a coercive force of at least 180 oersteds and being of such size and so posi tioned with ` respect to the armature that the ratio of the length of the flux path in the co ercive portion of the magnetic circuit to the com bined length of the> air gaps in the path through the 'air to the armature and return is less than v . . net and the driving element being on opposite 25 to l. 5. A watthonr meter comprising a torque pro sides of the disc, tend to shift the disc bodily in ducing electromagnet, a disc driven by the elec one direction so that the bearing has to counter . tromagnet and capable of continuous- rotation, act this force. Although but one embodiment of my invention and a damping magnet for said disc, said mag 70 has been herein“ shown and described, it is to net being of general horseshoe shape with its end. . be understood that the invention is not limited faces comprising pole faces both of which are thereby, but is 'to be limited only` by the prior art. adjacent one face of the disc» and having an The following claims are intended to point out armature cooperating with said pole faces adja 75 some of the features now recognized as new, cent the opposite face oí the disc, said magnet 8 andere being made of a material havingacoercive force face of the disc, said magnet being formed of a and so positioned with respect to the armature that the ratio of the length of the flux path in the 'coercive portion of the magnetic circuit to the combined length of the air gaps in the path through the air to the armature and return is than 180 oersteds and capable of operating above the point of its maximum energy product after being knocked down with a force corresponding less than 15 to 1. meter mechanism mounted on said base, said oi at least 180 oersteds, and being of such size ` magnetic material of coercive strength. higher _ 6. A watthour meter> comprising a torque pro ducing eiectromagnet, a disc driven by the elec tromagnet and capable of continuous rotation, and a damping magnet for said disc, said magnet beingA of generalhorseshoe shape with its end faces comprising pole faces both oi' which are adjacent one face of the disc and having an armature approximately coinciding in shape with the outer edges of the pole faces cooperating with. said pole faces adjacent :the opposite face of the disc, said magnet being made of a material 20 having a coercive force of at least 180 oersteds and being of such size and so positioned with respect to the armature that the ratio of the length of the iiux path in the coercive portion of the magnetic circuit to the combined length of the air gaps in the path through the air to the armature and return is less than 25 to 1.` 7. A watthour meter comprising a torque pro ducing electromagnet, a disc driven by the elec-_ tromagnet and capable of continuous rotation, a 30 damping magnet for said disc, said magnet being made in general horseshoe shape with its legs'ta to at least 120 oersteds. 10. A watthour meter including a base and a mechanism including a driving unit, a unitary frame formed'of a non-magnetic material re 10 movably secured' to said driving unit, a pair of spaced bearings carried by said frame, a disc ro tatable in said bearings and positioned by said `frame to be inductively acted upon by said driv ing unit, and a damping magnet carried by the frame with closely spaced poles adjacent one face of said disc, said frame extending around the. edge of said disc adjacent the pole portions of said magnetkand an armature carried by said frame opposite said magnet but adjacent the op 20 posite face of the disc. ‘ 11. A watthour meter including abase and a meter mechanism mounted on said base. said mechanism including Va driving unit, a frame formed of a non-magnetic material removably se 25 cured to said 4driving unit, a pair of spaced bear ings carriedby said frame, a disc rotatable in said bearings and positioned by said i'rame to be inductively acted upon by said driving unit, and damping magnet means carried bysaidl frame- 30 on the outside thereof and including closely pering toward their ends over a substantial por spaced opposed pole portions adjacent the same tion ofd their length and with its end faces com-> prising pole faces both of which are adjacent 'one face of said disci; said frame extending from the inside of .said damping magnet meansr between face of the disc and having an armature cooper said opposed pole portions and aroundlthe edge 35 ating with said pole faces adjacent the opposite of said disc. 7 face of the disc, said magnetl being made of a material having a coercive force of at least 180 oersteds, and being of such sizeand so positioned 40 with respect to the armature that the ratio of the length of the flux path in the coercive portion of the magnetic circuit to the combined length of the air gaps in the path through the air to the armature and return is less than 25 to 1. 8. A Watthour meter comprising a torque pro-y ~ 12. A watthour meter having a continuously rotatable disc, an electromagnet driving unit having current and voltage windings subject to abnormal surges, a damping magnet in close 4,0 proximity to such windings and in substantially unshielded relation with respect thereto. said damping magnet being in a magnetic state cor responding to its having been previously sub jected to knockdown force of at least '10 ampere 45 turns per -fnch of developed length of the mag-' Itromagnet and capable of continuous rotation, net and suilicient in magnitude for the magnet and a damping magnet for said disc, said magnet to withstand, with immunity ,from permanent being of general horseshoe shape with its end - weakening, the magnetic surges to which it is faces comprising pole faces both oi' which are ad- ' likely to be subjected in service in its environ 50 ment in the meter, the magnetization of said jacent one face of the disc and having an arma ture cooperating with said pole faces adjacent magnet being still above ,a value at which it has the opposite face of the disc, said magnet being approximately its maximum energy product. 13. A watthour meter having a continuouslyv made of a material having `a coercive force of at least 180 oersteds, and being of such size and so rotatable disc, an electromagnet driving unit hav-à 55 positioned with respect to the armature that the _ing currentand voltage windings subject to ab ratio of the length of the flux path in the coercive normal surges, a damping magnet in close prox portion of the magnetic circuit to the combined imity to such windings and in substantially un length of the air gaps in the path through the shielded relation with respect thereto, said damp ing magnet being made of a material having a 60 60 air to the armature and return is less than 25 to coercive strength of at least 180 oersteds and 1, and the entire magnet being located a sub stantial distance from the peripheral boundary being in ,a magnetic state corresponding to its >of the meter case wherebyl adjacency error is having been previously subjected to a knockdown . ducing electromagnet, a disc driven by the elec substantially eliminated. , i 9. A watthour meter forpolyphase measure-' ments comprising a plurality of independent y torque producing electromagnets, a disc driven bythe electromagnets, capable of continuous ro tation, and including a plurality of overlapping .sections substantially electrically isolated from force of at least 70 ampere turns per inch of developed length of the magnet and suiilcient 65 in magnitude for the magnet to withstand, with immunity from permanent weakening, the ymag lnetic surges to which it is likely to be subjected in service in its environment in the meter. 14. A watthour meter having a continuously one another and each acted upon by only one of » rotatable disc, and an electromagnet driving unit the driving magnets at a time, damping magnet > having current and voltage windings subject to means forming two adjacent opposed fields pass ing through said disc, and including at least one 75 magnet having both poles adjacent the same abnormal surges, a damping magnet system in close proximity to such windings having a mag- ‘ netic circuit forming an air gap through which 75 2,110,418 the disc rotates and including a magnet made of a material having a coercive strength of at being in a magnetic state _ least 180 oersteds and corresponding to its having been previously mag netized and then subjected to a knockdown force of at least '70 ampere turns per inch of developed length of. the magnet; the remainder of the magnet system having substantially no coercive strength, and the ratio of the length of the coer cive portion of the magnetic circuit to the total 10 air gap length in the magnetic circuit being less than 25 to 1. „ 15. A watthour meter including a continuously rotatable disc, a driving unit for rotating said 15 disc, and a damping magnet system including a tarding the rotation of said disc, said damping magnet being made from a magnetic material of coercive strength higher than one hundred eighty oersteds, having closely spaced poles ad jacent one face of the disc and being positioned substantially between vertical planes on each side of the meter passing through the periphery of the disc, and an armature opposite said magnet, adjacent the other face of the disc and directly 10 bridging the poles. 17. A watthour meter including a continuously rotatable disc, a driving unit for rrotating said disc, and a U-shaped damping magnet for re tarding the rotation of said disc, said damping` magnet being made from a magnetic material of' coercive strength higher than one hundred eighty closely spaced poles adjacent damping magnet for producing opposed and ad having one face of the disc and being positioned sub jacent concentrated iields cutting the disc, said‘V loersteds, damping magnet being made from a magnetic material of coercive strength higher than one hundred eighty oersteds, and said damping mag 20 net system being positioned between vertical »planes on each side ot the meter passing through the periphery of the disc. 16. A' watthour meter including a continuously a driving unit for rotating said g5_ rotatable disc, disc, and a U-shaped damping magnet for re stantially between vertical planes on each side of the meter passing through the periphery of the disc, and an armature opposite said magnet, adjacent the other face of the disc and approxi mately coinciding in shape with the outer edges of the pole faces of the magnet. 25 STANLEY S. GREEN.