US2541841A - Unidirectional flow in plurality chamber induction furnace - Google Patents

Description

3 Sheets-Sheet 1 F a g F i g. 4.

INVENTOR M 75m BY %ZWM ATTORNEY M. TAMA UNIDIRECTIONAL FLOW IN PLURALITY CHAMBER INDUCTION FURNACE Feb. 13, 1951 Filed June 20, 1947 Feb. 13, 1951 M. TAMA 2,541,841

- UNIDIRECTIONAL FLOW IN PLURALITY CHAMBER INDUCTION FURNACE Filed June 20, 1947 5 Sheets-Sheet 2 Feb. 13, 1951 M. TAMA UNIDIRECTIONAL FLOW IN PLURALITY CHAMBER INDUCTION FURNACE 3 Sheets-Sheet 3 Filed June 20, 1947 ATTORNEY Patented Feb. 13, 1951 UNITED STATES PATENT OFFICE UN IDIRECTIONAL FLOW IN PLURALITY CHAMBER INDUCTION FURNACE Mario Tama, Morrisville, Pa.,- assignor to Ajax Engineering. Corporation, Trenton, N. ..].v

Application .Iune2'0, 1947, SeriaI'N0. 7.55,,886

4 121Glaims.

This invention relates to an induction furnace and particularly to a multi-chamber induction furnace of the stationary and of the tiltable type. These furnaces are generally provided with two ormore' metal holding chambers or hearths and these chambers (or hearths) are connected by a system of channels or ducts forming the secondary melting loop; the channels are in the customary manner threaded by primary trans-.

former units.

The furnaces are frequently equipped with a rocking or rotating. device; the rocking of the furnace imparts to the molten metals an agitating and mixing action in order to equalize the metal charges held in the various chambers or transmission of theheat which is inductively created by the primary transformer unit or units to the metal charges in the various holding chambers.

' Prior attempts to impart to induction furnaces an effective and fast distribution of the inductively created heat to the molten metal charge and to produce uniform metal melts have been based on the production of a metal movement by the creation of temperature differences in the secondary melting channels, which for thi purpose were equipped with sections of a smaller and a' larger cross-area; it was assumed that" a higher temperature could be obtained in the places of smaller cross section whereby aonedirectionalmetal flow would be initiated. However, these and other attempts to create a unidirectional flowor circulation of the molten metal chargeininduction furnaces have remained entirelyunsuccessful.

-The' creation of a one-wayor unidirectional now of the metal is indeed highly desirable in induction furnaces and particularly in those of the submerged resistor type and many suggestions have been continuously made in the source of the past forty years to satisfactorily solve this problem.

2 These suggestions include: 7 The provision of" a plurality of separate and of moving electromagnetic fields,

Of open loop reservoirs for" the charge and closed loop channels connecting with the reservoir at remotely separated places.

The arrangement of hearth entering ends of the loop at vertically different levels,

The-gradual enlargement of the loop cross-area from one to the other hearth entering points,

The co-axial arrangement" of the primary and the secondary and The displacement from each other in an axial direction.

Some of the known constructions utilize the;

pinch-effect and some have been designed with the purpose to prevent the disruption ofthe metal flow'by the latter.

The above recited numerous endeavors demonstrate the importance of a satisfactory flow control of the molten metal in induction furnaces; but none of them has attained the status of practical usefulnessbecause they are based on constructional changes of the secondary loop itself.

Even. if a unidirectional. pressure fiow'is shown in the prior art from one outlet of'thesecondary' loop. through. the; charge into. another .outlet of thexloop and areturn flowthrough the latter, this flow is; on. account. of: the heavy weight: of the: superposed metal charge-,necessarily confined tov its lower; portion; this; is particularly true of' deep-chargeswhere the flow-impetus of the metal: emerging. from the. loop into. the hearth is. soon counteracted by the weight of. the charge;

As mentioned above, the movement of the at the emergence point. of themelting' channels into. the hearth effecting a direct return movement of the molten charge-into the same channels.

The metal flow produced by the pinch effect in a submerged resistor type induction furnace having a melting loop composed of a channelspaced: from the hearth and apl'ura'lity ofsubstantially straight channels connecting: the

spaced channel with the hearth is illustrated in attached Fig. 1', showing the meltingloop and the bottom section of the hearth.

Theelectromagnetic field of highest intensity is located inthe center section of the straightmelting channels 5 at" about half their length.

The metal is formedfiom this center section at an upward and in a downward direction through the melting channels, as indicated by the arrows. The molten metal stream emerging from the ends of the channels draws the metal from adjacent portions of the charge into the same channels, whereby two lateral fiow branches result which are again outwardly forced as they approach the center portion of the channels. Under the direct influence of the electromagnetic, field the well known flow of the melt in opposite directions results through the same channel, as shown for instance in U. S. Patent Sasnett No. 1,660,209 and indicated by the arrows in Fig. 1.

Within the range of its highest intensity the electromagnetic field has the tendency to compress the molten conductor; if the current input is sufficiently high, it may happen that the conductor is interrupted or pinched; thus the term pinch effect was created.

However, and as above stated, the direct return of the metal into the melting channel is the consequence of the metal pressure produced by the electromagnetic field and the resulting sucking effect in coactlon with the pressure distribution in melting channels; it will therefore not take place in those portions or layers of a molten metal charge, which are not influenced by the electromagnetic field.

The pressure distribution resulting in the adjacent sections $-.')3 and yy at the transition point of the metal from the channel mouth into the hearth is illustrated in Figs. 2 to 5.

The hydrostatic pressure HP which increases from the surface of the melt downward is shown in Fig. 5; at the point a: it is HX, at the point 1 it is Hy.

The pinch effect produces a superimposed inwardly directed pressure which, as can be shown by simple calculation, increases on a parabolic curve from the periphery of the channel toward its center, where the pressure attains its maximum. This pressure is wheregI denotes the current and r the radius of theconductor.

TtIt'is obvious that the pressure maximum Py in the smaller section y-y is smaller than the pressure PX in the larger section r--r. The adjacent points a and b are consequently subjected to various pressures and, as will appear from Fig. 4, the pressure at b is higher than that at 2, Fig. 3. This causes the liquid conductor to be squirted-out in the direction b to a; the metal upwardly propelled in the direction of the center arrow is replaced by metal drawn back from adjacent portions of the charge, as shown by the lateral arrows in Figs. 1 and 2. A similar metal'flow is produced at the emergence of. channels 5 into channel 6, Fig. 1.

This metal transport through the melting channels of the furnace has its advantages; it prevents, for instance, the overheating of the metal in the melting channels. However, the non-controlled metal movement is locally limited and obviously insufficient to have a decided influence on the equalization of the charge and the distribution of the heat thereto; moreover, the current input is limited and the high power factor required for the steadily increasing capacity of modern induction furnaces cannot be obtained because current increase involves the danger of the conductor being interrupted in the zone of the highest field intensity. Some of the known suggestions to create a unidirectional flow also involve difficulties in the construction of the furnace itself and greatly raise its manufacturing costs.

It is therefore the primary object of this invention to create in a multi-chamber induction furnace an equalization of the metal melts in the various chambers and'uniformity with regard to chemical composition and temperature.

It is a further object of the invention to achieve this aim without rocking the furnace and without the application of rotatable devices, such as supporting rollers and the like.

It is another important object of the invention to create in these furnaces a continuous unidirectional closed metal flow through the various chambers with adherent uniformity of the metal in the same; this is of particular importance in the mass-foundry and die-casting practice of,

particularly, light metals where the production of uniform castings is a dominant postulate which has hitherto not been satisfactorily met within the customary mechanically rocked induction furnaces.

It is a further object of the invention to permit a practically unlimited increase of the power factor or current density without incurring the. danger of interrupting the conductor or clogging.

the melting loop.

It is a further important object of the inven tion to successfully melt in these furnaces smallsizedmetal materials such as scrap, turnings,

borings, chippings and even fine metal powders.

It is a further Object of the invention to optionally increase the power factor of the furnace and to obtain with the same amount of iron in the transformer a larger power input.

It is also an object of the invention to greatly reduce slag deposition in the melting loop and particularly in the center section of the melting channels as the continuous unidirectional metal flow through the entire channel length prevents the slag particles from coming to rest.

With the above recited and. other objects in.

in an opposite direction from the first chamber through the melting loop into the other chamber.

In this manner, the molten metal is forced to, participate in a continuous one-way or unidirec tional circulation through the various chambers and a highly satisfactory equalization of the charge is obtained which is far superior to the rocking of the same, is far less expensive and is equally applicable to stationary and tiltable furnaces.

The inductively created heat is equally and uniformly distributed throughout the entirecharge of the various chambers. Small-sized metal scrap and metal powders may be molten without difliculty, which hitherto has been unattainable in multi-chamber induction furnaces.

A simple means to obtain the above described closed and unidirectional flow of the entire charge consists in the location of a current conductive refractory tube, for instance, a graphite or carbon. tube in: a melting channel or directly above. its upper end. in. such. amanner that. the tube forms an extension of the channel; the tube;

ends within. or above a section of the melt: which is practically free from the influence of the. in-.

ducedelectromagnetic. field- The invention-relates to an induction furnace ofthe submerged resistor type. as. disclosed. in

copending U patentv applications Serial No- 647,831, filed. Feb. 15, 1946, now Patent No. 2,536,325,.v issued. Jan. 2,1951; Serial No- 683,115.,

filed. July 12,, 1946, now Patent. No- 2,539,215,. issued. Jan.. 23,1951; Serial No. 671,818, file'dMay 23,. 1946, now Patent No. 2,536,859, issued Jan. 2,. 1951.; and Serial No. 735,851, filed, Mar- 20, 1947.

The invention is. basedon the general idea also inherent inthese .copending. patent applications.

oficreating, in the submerged resistor type furnace a unidirectional metal flow from. the melting loop into a zone which is essentially free. from inductive influence;,for this: purpose a, refractory tube is inserted. with; its one end into the melting: loop; the tube reaches; with. its other end into a. zone. which. is essentially not influenced by inducmetal froman induction furnace by inserting av refractory, current-conductive tube into a meltingchannel; certain claims. include the maintenanceof a small clearance between the. outside of the. inserted tube and the inside of the melting duct, the insertion of an additional refractory tube into the melting channel and the application of the unidirectional flow principle to a duplex induction furnace consisting, of a large capacity and a small capacity melting furnace.

:Patent application. Ser. No. 735,851, filed Mar...

20,, 1947, claims the creation of a unidirectional closed metal flow within the melting loop and the hearth of asingle induction furnace by the connection of a refractory, current conductive tube with the melting loop.

The. present application claims the application of the above recited general inventive idea of creating a-unidirectional metal flow by the insertion of a refractory tube into a melting loop to an induction furnace having a plurality of chambers connected by this loop and the creation of the closed metal flow through these chambers andthemelting loop.

. Induction furnaces embodying the hitherto known metal movement in the melting channels and. the. one-way or unidirectional circulation of the melt in accordance with the invention will now be described in detail and with reference to the attached drawings.

;In the drawings,

Fig. 1 is a vertical section of the lower part of a submerged resistor type inductionfurnace illustratingv the customary metal. flow under the influence of the. pinch effect,

Figs. 2-5 illustrate the pressure conditions which prevail in. this furnace at the emergence of the melt from a melting channel into the hearth,

Fig.6 is a'vertical section of a double. chamber.

induction furnace online 66 of Fig. 7, equipped; to produce a unidirectional meta1 circulation. through both furnace chambers according to this invention,

Fig. 7: is a sectional view on line 1--! of Fig. 6, Figs. 8, 9 and 12- are vertical sectional views of further modifications of the tiltable doublechamber furnaces shown in Figs. 6 and 7.

Fig. 10 is a vertical sectional view of a threechamber furnace on line equipped in conformity with this invention,

Fig. 11 is a. sectional view of the same furnace on line l.l- |l of Fig. 10,

Fig. 13 is a verticalsectional view of the furnace. similar to that of Fig. 6 showin a further modification.

The. furnace shown in Figs. 6 and 7 is equipped. with two metal holding chambers or he'arths 1, 2.

l The secondary melting loop is located between these two chambers.

The loop consists of three melting channels 3, 4, 5 which connect the two chambers I, 2 and are threaded by primary transformer units composed of coils 6 of insulated copper wire and an iron core 1 which is closed toward the coil windings.

The furnace is housed in casing B lined witha: refractory material 9, has a pouring opening I9, covers ii, closing plugs l2, and is tiltably supported in bearings i9; customary means, such as electric hoists and hydraulic cylinders, will be- .provided to effectuate the tilting.

As apparent from the drawings, the melting channels 3, 4, 5 are parallel and equally inclined in such a manner thatstraight cleaning tools can be inserted through the openings'closed by plugs I2 into the channels while the same are full with the molten metal. Therefore the furnace can be kept in full operation during the cleaning of the melting channels; this is true for the position shown in the drawings and for any tilted position of the furnace. In the hitherto known multichamber furnaces of this type the furnace had to be emptied for the insertion of the cleaningtools and the cleaning of the melting channels.

from the outside of the furnace could not be effected in the tilted position while the furnace was in operation and the melting channels were kept full ofv the molten metal.

The means creating the homogenization of the metal in the two chambers I, 2 consist of a current conducting refractory, for instance, graphite tube 13 which, as illustrated in the drawings} is inserted into channel 3; however, these tubes may be also inserted in the lateral channels,

whereby the metal circulation would be reversed insofar as the metal will then flow from channels l, 5 into chamber 2, from there into channel 3, then through chamber I and back into chan-- nels 4, 5.

The free end of tube [3 extends into a section of the metal bath held in chamber 2' which is practically free from the influence of the electromagnetic field; the proper length of the tubewill vary in accordance with the particular operating conditions of the furnace; however, that section of the hearth which is practically free of induced current and which therefore decides the length of the tube may be ascertained without. difficulty as the extent of the electromagnetic field,

produced in these furnaces can be easily determined.

The upper or front portion of tube l3, which is 1 not under the influence of the electromagnetic field, is protected by a body of a suitable retrac l9--lll of Fig. 11

7 tory material, such as refractory brick l8, to prevent the breakage of the tube by the metal which is charged into the furnace chamber 2. The portion of the tube directly adjacent to the transformer unit, however, remains unprotected and leaves the way open for the flow of the current through the electrically conductive tube 13.

Due to the fluid pressure created by the induced electromagnetic field in channel 3 the metal is forced to flow from tube l3 in the direction of arrows [6; the outfiowing metal is replaced by metal flowing in the direction of the arrows from chamber I into channel 3; accordingly metal must flow from chamber 2 through channels 4, into chamber I and from there again into channel 3.

In this manner a steady continuous one or unidirectional circulation of the charge is produced through both chambers and a thorough homogenization achieved of the melts in the two chambers without the application of mechanical or furnace rocking means.

The tube 13 may extend, if desired, through the whole length of the melting channel as illustrated in Fig. 13.

In the modification of the invention shown in Fig. 8 the tube is so inserted into channel 3 that it extends into chamber I. The metal flow will accordingly be reversed to that shown in Figs. 6 and 7. However, the unidirectional circulating and homogenizing action of tube I3 remains unaltered.

In the furnace shown in Fig. 9 which otherwise is not different from those shown in Figs. 6-8 arcuated melting channes are provided which con trary to the furnaces of Figs. 6 and 8 could not be cleaned by straight cleaning tools during the operation of the furnace.

The furnace shown in Figs. 10 and 11 is a three chamber furnace which is equipped with metal holding chambers l, M, 2.

Two secondary melting loops are located between chambers l and I4 and between chambers 2 and I4. The loops consist as in the case of the previously described furnaces 8 to 9 of melting channels 3, 4, 5 which connect the metal holding chambers and are threaded by the primary transformer units composed of coils S of insulated copper wire and iron cores 1.

The furnace is housed in a refractory lined casing 8, has covers H for the three chambers and sealing plugs 12.

The means for creating the unidirectional metal circulation from the center chamber M into the lateral chambers l and 2 and the return flow into center chamber 14 consist of the refractory cur m rent conductive tubes l3 inserted into the center channels 3.

The free ends of tubes l3 extend, as previously described, into a section of the metal bath which is substantially free from the influence of the electromagnetic fields created by the inductor units. The refractory protective brick I8 may also here be applied to tube l3 in the previously described manner.

Due to the extension Of channels 3 by the tubes I3 the metal flows from these tubes into chambers I and 2, from there through channels 4, 5 into the center chamber 14 and back into channels 3; thereby the same continuous unidirectional metal flow, as previously described, is created in a three chamber furnace.

As apparent from Fig. 12, the invention is here applied to a double-chamber furnace where the melting channels are only accessible to the introduction of cleaning tools after the charge has been emptied-out; the furnace is otherwise equipped in the same manner as the furnaces shown in Figs. 6 to 9.

As previously mentioned, the here described furnaces are particularly well suited for the melting of metal scrap and also light metal scrap. The heat is generated at the bottom of the furnace and immediately transferred to the cold scrap from the melting channels by liquid contact due to the continuous unidirectional metal flow. Therefore the fine metal particles are not subjected to high temperature from above. Hence the rate of oxidation before melting is reduced considerably. As a further consequence of the unidirectional bath movement, the heat transfer and therefore the speed of melting is considerably increased and any oxide formed is detached from the scrap particles and expelled to the surface of the bath.

1 claim:

1. In an induction furnace, a plurality of chambers located in spaced-apart relationship for holding molten metals, at least one secondary loop composed of a plurality of melting channels connecting the said chambers, at least one primary transformer unit threading said secondary melting loop adapted to create an electromagnetic field and to hold the metal in said chambers in the molten state, means for the production of a unidirectional closed circulation of the molten metals between the said chambers through the melting loop, said means including a refractory current conductive tube extending from a melting channel into a chamber below the normal operating level of the metal and shifting the connection of said melting loop with said chamber into a chamber section of reduced electromagnetic field intensity.

2. In an induction furnace, a plurality of chambers located in spaced-apart relationship for holding molten metals, at least one secondary loop composed of a plurality of melting channels connecting the said chambers, at least one primary transrormer unit threading said secondary melting loop adapted to create an electromagnetic field and to hold the metal in the said chambers in the molten state, means for the production of a unidirectional closed circulation of the molten metals between the said chambers through the melting loop, said means including a refractory current conductive tube extending from a melting channel into a chamber below the normal operating level of the metal and shifting the connection of said melting loop and said chamber into a chamber section which is free from the influence of the induced electromagnetic field.

3. In an induction furnace, a plurality of chambers located in spaced-apart relationship for holding molten metals, at least one secondary loo composed of a plurality of melting channels connecting the said chambers, at least one primary transformer unit threading said secondary melting loop adapted to create an electromagnet field and to hold the metal in said chambers in the molten state, means for the production of a unidirectional closed circulation of the molten metal between the said chambers through the melting loop, said means including a current conductive refractory tube connected with its one end to an outlet of the loop into a chamber and terminating with the other end beneath the normal operating level of the metal in a section of the metal holding chamber which is substantially'free from the influence of the .-.rilectmnnag netic field.

4. In an induction furnacaa pluralityof chambers located in spaced-apart relationship for holding molten metals, at least one secondary ductive refractory tube inserted with the oneend into a melting channel and terminating with the other end beneath thenormal operating level of the metal in a section of the metal holding chambar which is substantially'free from the influence of the electromagnetic field.

5. In an induction furnace, two chambers located in spaced-apart relationship for holding :molten metals, a secondary loop composed of melting channels connecting the bottom portion of the two chambers, at least one primary transformer unit threading the said secondary melting loop adapted to create an electromagnetic field and to hold the metal in the two chambers in the molten state, means for the production of a unidirectional closed circulation of the molten metal between said chambers through said melting 100p, said means including a clll'lfllt conductive refractory tube connected with its one end to an outlet of the melting loop into a chamber and extending with the other end beneath the normal operating level of the metal into a section of said chamber which is substantially free from the influence of the electromagnetic fi'ld.

6. In an induction furnace, two chambers located in a spaced-apart relationship for holding molten metals, the bottom of the said chambers being at different levels, a secondary loop composed of inclined melting channels connecting the bottom portion of the said two chambers, at least one primary transformer unit threading the said secondary melting loop adapted to create an electromagnetic field and to hold the metal in the two chambers in the molten state, means for the production of a unidirectional closed circulation of the molten metal between said chambers through said melting loop, said means including a current conductive refractory tube connected with the one end to an outlet of the said melting loop into the chamber having its bottom at the higher level and extending with the other end beneath the normal operating level of the metal into a siction of said chamber which is substantially free from the influence of the electromagnetic field.

'7. In an induction furnace, two chambers located in a spaced-apart relationship for holding molten metals, the bottom of the said chambers being at, different levels, a secondary loop compos:d of inclined melting channels connecting the bottom portion of the said two chambers, at least one primary tranformer unit threading the said secondary melting loop adapted to create an electromagnetic field and to hold the metal in-the two chambers in the molten state, means for the production of a unidirectional closed circulation of the molten metal between said chambers through said melting loop, said means including a current conductive refractory tube connected with the one end to an outlet of the melting loop into the chamber having its bottom at "the lower level and extending with the other end beneath the normal operating level of the metal into a section of said chamber which is substantially free'from the influence of the electromagnetic field.

-8. In an induction furnace, a center chamber and two lateral chambzrs located in spaced-apart relationship for holding molten metals, secondary loops composed of a plurality of melting channels connecting the said center chamber with the said lateral chambers, at least one primary transformer unit threading each of "the said secondary melting loops adapted to create an electromagnetic field and to hold the metal in said chambers in the molten state, means for the production of unidirectional closed flow s of the molten metal between the :center and the lateral chambers through said melting loops said means including current conductive refractory tubes connected with the one end to an outlet of the loops into a chamber and terminating with the other end below the normal operating level of the metal in a section of the metal holding chamber which is substantially free from the influence of the el:ctromagnetic field.

*9. In an induction furnace, a plurality of chambers located in spaced-apart relationship for holding molten metals, at least one secondary loop composed of a plurality of melting channels connecting the said chambers, at least one primary transformer unit threading said secondary melting loop adapted to create an electromagnetic field and to hold the metal in said chambers in the molten state, means for the production of a unidirectional closed circulation of the molten metal between said chambers through melting loop, said means including a current conductive refractory tube connected with its one end to an outlet of the loop into a chamber and terminating with the other end beneath the normal operating level of the metal in a section of the metal holding chamber which is substantially free from the influence of the electromagnetic field and a refractory metal resistant protective body applied to the said tube on a major portion of its length extending in a metal holding chamber.

10. In an induction furnace, a plurality of chambers located in spaced-apart relationship, for holding molten metals, at least one secondary loop composed of a plurality of melting channels connecting the said chambers, at least one primary transformer unit threading said secondary melting loop adapted to create an electromagnetic field and to hold the metal in said chambers in the molten state, means for the production of a unidirectional closed circulation of the molten metal between said chambers through melting loop, said means including a graphite tube connected with its one end to an outlet of the loop into a chamber and terminating with the other end beneath the normal operating level of the metal in a section of the metal holding chamber which is substantially free from the influence of the electromagnetic field.

11. In an induction furnace, a plurality of chambers located in spaced-apart relationship, for holding molten metals, at least one secondary loop composed of a plurality of melting channels connecting the said chambers, at least one primary transformer unit threading said secondary melting loop adapted to create an electromagnetic field and to hold the metal in said chambers in the molten state, means for the production of a unidirectional closed circulation of ten metal.

the molten metal between said chambers through melting loop, said means including a carborundum tube connected with its one end to an outlet of the loop into a chamber and terminating with the other end beneath the normal operating level of the metal in a section of the metal holding chamber which is substantially free from the influence of the electromagnetic field.

12. A method of producing homogeneous metal melts in multi-chamber induction furnaces which are provided with a secondary loop composed of melting channels connecting the chambers and with at least one transformer unit threading said loop and adapted to create an electromagnetic field, comprising holding by means of the said field a metal charge in the said chambers in a molten state, advancing the outflow of the metal from a melting channel into a section of a metal holding chamber which is substantially free from the influence of the said electromagnetic field, creating a continuous unidirectional flow of the metal through the said chambers and the said melting loop and obtaining hereby complete homogenization of the mol- MARIO TAMA.

12 REFERENCES crrnn The following references are of record in the file of this patent:

5 UNITED STATES PATENTS Number Name Date Re. 22,602 Tama Feb. 13, 1945 1,312,069 Wyatt Aug. 5, 1919 1,660,407 Bainbridge Feb. 28, 1928 10 1,792,449 Spencer Feb. 10, 1931 1,793,137 Russ Feb. 17, 1931 1,944,855 Wadman Jan. 23, 1934 2,339,964 Tama Jan. 25, 1944 2,375,049 Tama May 1, 1945 15 2,381,523 Tama et a1. Aug. 7, 1945 2,386,369 Thompson Oct. 9, 1945 2,397,785 Friedlander Apr. 2, 1946 FOREIGN PATENTS 20 Number Country Date 126,947 Great Britain Dec. 24, 1919 142,110 Great Britain Apr. 20, 1920 788,006 France July 22, 1935

Images