US2612356A - Homogenizing device - Google Patents

Description

A. G. BORCK HOMOGENIZING DEVICE Sept. 30, 1952 6 Sheets-Sheet 1 Filed May 9, 1951 Sept. 30, 1952 BQRCK 2,612,356

HQMOGENIZING DEVICE Filed May 9, 1951 s Sheets-She et 5 r' r'. I g r I INVENTDR. A/fi'ed Gerhard Borck Sept. 30, 1952 A. G. BORCK v HOMOGEINIZING DEVICE 6 Sheet Q 4 ENToR Alfred Gerh Borck BY I Patented Sept. 30, 1952 .IIOMOGENIZING DEVICE Alfred Gerhard Borck, Tullinge, Sweden, assignor to Aktiebolaget Separator, Stockholm, Sweden,

a corporation of Sweden Application May 9, 1951 Serial No. 225,291

. In Sweden May 12, 1950 20 Claims. (Cl. 259-96)v This invention has to do with homogenizing liquids, and particularly with an improved device for this purpose. I

Homogenizingrequires energy. For a long time it has been the commonpractice to force the liquid, which is to be homogenized, under high pressure (up to several hundred kgs./cm through a slot, often consisting of a spring-loaded valve and its seat. It was thought that the degree of homogenization depended primarily on the pressure, so thatin order tov improve the homogenization the first thing to do wasto increase the pressure. Latest experience, however, 'shows that it is possible to obtain with a much lower pressure as good anhomogenization as that obtained with the higher pressureused in the prior homogenizing devices. For example, a socalledwhirl chamber has been used, often combined with a cyclone, in order to achieve a high turbulence or other whirling movement of the which is primarily decisive, but the nature of the homogenizing device. If the liquid is driven into a whirl chamber at ahigh speed, particularly from a cyclone-by means of which the liquid stream is set in rotation, a good homogenizing result is obtained with the use of a considerably lower pressure than that previously employed in prior homogenizing devices. Homogenizing members of other types, for example, chambers containing bodies of a suitable shape, such as filings,

have'also yielded good results with relatively low pressures. v In connection with the homogenizing, a treatment in a centrifugalseparator is often'carried out, as in the case of homogenizing milk. In this case, it is desired to purify the milk in connection 'With' the homogenizingyan d the purifying operation is preferably effected in a centrifuge. It is also advantageous to separate the skim milk prior to the homogenizing, so that only the cream has to be passed through they homogenizing device, whereupon cream and skim milk are remixed. this Waya considerable saving of energy is made possible.

" It'is'often desirable"to, standardize the milk in connection with the homogenizing. By the standardization, a certain predetermined fat content is given to the milk, and this operation is effected in connection with the centrifuging by conducting away a part of the cream or a part of the skim milk while the main part of the it possible to conduct away the cream to efiect a standardizing in connection with the homogenizing and centrifuging, in an economical manner.

In a centrifugal bowl, the liquid under treatment has the same angular velocity as that 01' the bowl. Some distance from the axis of rotation this velocity and the static pressure existing there involve a considerable amount of energy. When the liquid is discharged by means of a paring device, the velocity energy may be converted into pressure energy in the paring device. In addition, there exists the static pressure prevailing at the inlet of the paring device. Thus, it is possible to bring about a considerable conversion of energy in the paring device. According to the invention, this fact is utilized to ensure a good homogenizing. This may be achieved by providingthe paring device with a suitable homogenizing member, for example, a whirl chamber (together with a cyclone, if necessary) or with a set of balls. In this case, a super-pressure is generated in the inlet of the paring device, by which therliquid is forced through the homogenizing member. It is also possible to utilize more directly the flow velocity of the liquid. The liquid may, for example, flow at unchanged velocity into a cyclone communicating with the paring device and then into a whirl chamber also communicating withthe paring device.

The present invention is characterized principally by a rotating container arranged to force the liquid contained in it to partake in its rotation, and by a discharge member projecting into the liquid during operation, in the form of a paring disc, for example, and by a homogenizing device connected with the discharge member or formed therein. A construction of this type may be used for homogenizing without centrifuging but it may also to advantage be built into a centrifugal bowl in which the liquid is subjected to some other treatment in connection with the homogenizing, for example, separation or purification or both. I

The accompanying drawings show by way of example some embodiments of the invention. Fig. 1 is'a vertical axial sectional view through 3 an homogenizing device made according to the invention; Fig. 1A is a horizontal sectional view of part of the paring disc in Fig. 1; Fig. 2 is an axial sectional view of a centrifugal bowl, made according to the invention, provided with a paring disc .tdeffect the homogenizing and with a second smaller paring disc for discharging the treated liquid from the bowl; Fig. 3 is a similar view of another embodiment in which the centrifugal bowl is also provided with a paringmember for the homogenizing but in which the'outlet of the treated product is hermetically con nected to the centrifugal bowl by a collar; Fig. 4 is an axial sectional view of a paring member designed for homogenization; Fig. 5 is a plan view, partly in section, of a modified form of the paring disc; Fig. 6 is an enlarged vertical sectional view of the nipple in Fig. 1; andFigs. '7, 8 and 9 are vertical sectional views of further :modifications' According to Fig. 1, the liquid to behomogliquid-is conducted through a number of channels: or bores-61 into a circular paring. chamber 68 enclosing a paring member 3l38. Radial wings 69 arefixed to the part 63-above the paring member. which consists of lower andupper annular parts -'3-'l.:andSm-respectively. The upper part 38-is .-.provided,with a -depending peripheral flange 39 surrounding 1 an upwardly extending peripheral flanges of the part 31. .cber of nipplesor pins lH- are inserted which project rradially some: distance outside the part 38. :Duringioperation, .th6"Ol1trf part of the paring --member -31-'- 38'.is;enclosed ina rotating liquid. It is desirable that. the. free-surface of the rotat- .--iI-1g, liquid; whichis cylindrical, be positioned out- -side;thef fiange-39,-so' that only the nipples. --projectfinto-the liquid. Any friction between the rota-ting liquid, and thes'tationaryparts 3'I.-39

The-tube I carries the paring member,

In the flange 39, a numis thereby-avoided. On the other hand-agrelafrictionain. turnyentails a considerable (sometimes intolerable) heating of the liquid under treatment, and also a corresponding large consumptionof energy to operate the apparatus. It

is'therefore desirable that the level of the liquid vhe'situated wholly outside the flange 39, so that only the nipples project into it during operation. In order to-avoid the admixture of air referred to when the-level is positioned'as described, it is desirable .to use streamlined nipples .Each nipple 4 I. contains. a radially cylindrical chamber 42 arranged to form a cyclone together with an inlet to the chamber. The inlet consists .of an opening in the form of a narrow 510mm positioned tangentially in relation to the chamber 42 and having its orifice directed against the direction of movement ofth'e liquid, as indicated .4 by the arrow in Fig. 6. A whirl of the cyclone type is thus formed in chamber 42. The liquid leaves the chamber, through a central opening 43, in the form of a rotating liquid jet which penetrates into an inner whirl chamber 44 betweenthe; paring members3l-P-38. .In the neightively large quantity of air follows the liquid into .the'paringmember 31-48 through its inlets Ala :(Fig. 6) ,which are positioned in the nipplestl. In some cases it may therefore be advisable to :allo'wthe rotatingliquid to more or less over- .borhood of the opening 43,. the chamber-'44 is provided with a discharge channel 45 which conducts the liquid via another channel 45a into a central .chamber 46 which, by a channel 64 enclosing the pipe communicates with an outlet for the homogenizedliquid from the paring device. The paring. disc iszprovided with any desired number of: circumferentially'spaced nipples 4| with whirl chambers of. the type described.

The feed tube I is supported by a part 65 which during operation'is fixed to a frame (not shown) by a hood 66.

Referring to Fig. 5,-"fthe paring member there showncomprises adisc 48 provided with :one or more segments 49 each havinga cyclone chamber 42a. The whirl chamber Macommunicating with the chamber 42a is positioned .in-the .main part of the paring disc- 48 and consists of arad-ial bore therein. The channel 45eis formediby a space between theparts. 4 8 and 49. This space also contains a packingtll. The channel 45a connects the outer portion-of whirl chamber Me with the chamber by way of channel 5|. The

tangentially directed inlettla of chamber 42a ends at the'lower side of-the segment- 49.- With rotation of-the bowl. I Fromkchamber, 2a, which is positioned in-adistributor 5, the liquidproceeds through a number of channels 6. into-:aset. of conical discs 1 in which it is separated in the usual manner into a lighter componentflowing .inward toward therotationaxis, and aheavier component flowing outwardtoward-a sludge space 8. .The lighter component discharges through an-annular channel'9 betweenatop disc Ill and the distributori into a paringchamber II. The

latter is provided in the usual ,mannerwith radial wings I2 and l3rotatingwith the-bowl andpositioned above and below a stationary paring disc 14 in. chamber ll,the:disc [4 being supported by the inlet pipe 1a. After having entered the paring disc [4 and having been homogenized therein by a suitable device, (for example, by the arrangement illustrated.- in Fig. '5 and including the cyclone chamber 42a and whirl chamber 44a) the lighter component is ledback through channels l5 into the receiving chamber 2min which it :is mixed with the liquid delivered through pipe Ia.

Whenhomogenizinga liquid incident to its discharge from the paringchamber II by. means of the paring disc 14, the particles or drops of the liquid to be atomizedaresplitup intoea much greater numberof particles or drops which, however, vary considerablyin size. .When these drops or particles enterthe set of. discs-1, the smaller particles follow the heavier. liquid. component outwardly, whereas the larger accompany the lighter component "inwardly and are therefore again su'biect'ed to the atomizingfprocess" in paring disc'll. The heaviercomponent iszcollected in the sludge space 8 whence it. proceeds through another set of conical discs [6 inward into acollecting cha'mbe'rl'! and then througha channel 18 outside the paring chamber ll into a smaller paring chamber l9 positionedab'ove the chamber II and containing another smaller paring disc '20 whichis also supported'by the pipe la. The 'paring' chamber 19 is provided with rotating ra- 'dialwings 2i and 22 positioned above and below the paring disc. The paring disc 20 is provided with a number of channels 23 extending from the periphery "inward and communicating with axial channels 24 ,"whichextendupward through the rotor outlet 8a to a fixed discharge pipe 25.

The pipe la is fixed to'a stationary part 28 forming a hood'fillust'rated inpartlwhich covers the centrifugal bowl. The pipela is secured to the 'part'26 by a nut 21 forming one-half 28 of a coupling, the other half of which is fixed to a feed I pipe (not shown).

j 7 When treating milk, for example, in this centrifuge for homogenization andpurification, the primarily lighter component separated between the discs I is led via passage 9 and chamber I I through ally larger, is conducted via disc set l6, channel l8 and chamber H! to the smaller parin disc 23, by which it is discharged from the centrifugal bowl. The product thus discharged contains the entire fat content of the milk fed into the centrifuge, although in so finely divided form that the fat cannot be separated through the centrifugal force but follows the heavier component. This applies to conditionsprevailing when a state of permanency has been attained. The device operates with recirculation of those fat drops or. balls which were unsufficiently split up during the first homogenization. The separating efiect in the discs 1 ensures that all particles or drops over a certain size, for example, 0.8 are prevented from followin'gthe milk current discharging outward in the discs! 'anclfurther through the discs Hi and the paring disc 20 from the centrifugal bowl.

' The embodiment illustrated in Fig. 3 is characterized in that the homogenizin paring disc has an outward outlet, as contrasted with'the embodiment shown in Fig. 2. In this case the liquid to be treated is assumed to be fed in through passage in the centrifuge spindle S at the lower part of the bowl 8. As in Fig. 2, this liquid is first conducted to the set of discs 1 in which it is separated into a lighter and a heavier component. The lighter component passes inward to the central part of the bowl from which it is led through channels 30a and 30 into paring chamber ll which maybe identical with that shown in Fig. 2. Thus, 'it isprovided with radial Wings 12 and I3 positioned above and below a paring disc M. The latter includes an homogenizer which may be identical to the homogenizing arrangement 42a44a' illustrated in Figs. 2 and 5. From the paring disc l4, the homogenized liquid flows through a system of discharge passages 3| into a fixed return pipe 32, the continuation of which (not shown) communicates with the feed pipe S of the centrifuge along a return path 32a. The homogenized liquid is herein mixed with the untreated liquid and then reintroduced'into the set ()1 discs I, in which insufiiciently atomized parti cles or drops are separated andiollow the lighter component inwardly and are again'treated-in the homogenizing device of the paring disc -l-4.-"''Ihe sufficiently atomized drops or -particles .follow the heavier component into the sludge space. 8.v and proceed into a'purifying set ofdiscs l6 and'then finto a central outlet tube 32 and into a fixed discharge pipe 34 'connectedto the outlet pipe 33"by a packing collar 35. Outside the orifice. of the pipe 33 is a pump wheel 36 rotating'with-the'cen- 'trifugal b'owl'and serving to generate a higher In'Fig. '7, I have shown a paring disc'provided with an homogenizing device and dififerin'g'from that of Fig. 1 mainly in that the common-'axis'of the cyclone chamber 42b and the whirl chamber 44b is parallel with the rotation axis of the bowl or rotor 60b instead of perpendicular to it The paring disc 12 is supportedby the feed pipe lb and has at its periphery a number of cylindrical chambers 421) provided with tangentially directed inlet channels "H, arrangedin a manner similar to that of Fig. 6. Theinlet H forms a, narrow slot, the orifice of whichis rectangu lar and positioned at the outer cylindrical surface of the paring disc. The liquid passes through the central outlet 43b of the chamber 42b into .the whirl chamber'44b and then back into a channel 45 and furtherthrough channels 64b to the outlet." The paring chamber 68 is provided with conveyor wings 69 and 10 arranged in the rotatable housing 601) and forcing theliquid arriving throughpipe 'lb and chamber 2b'to partake in thegrotation of the housing 601). r v

In thehomogenizing device illustrated in. Fig.

8, the paring. disc is provided with a homogeniz- V ing member in the form of a set of balls 15 forming constricted passages forthe liquid. The pipe lc carries a disc-shaped part 13 comprising-ta chamber 420, the inlet .orifice 14 of which is positioned in the outer part of the lower sideof the disc 13. The inlet 14 is positioned tangentially in relationto the generally radial chamber 420, so that a rotating body ofliquid is formed in the chamber during operation; The chamber communicates in its. inner part with an homogenizing chamber containing a plurality of the closely packed balls 15, all of which are of. the same size. The wall 16 of the ball chamber projects only, a short distance into the chamber 42c so that the rotation of the liquidisfnot substantially impaired. The wall is providedwith an oblong slot 11, the longitudinal direction of which is parallel with thedirectionj' of flow. of the'liquid. The liquid gradually flows through this opening into the set of. balls 15 and. passes between the balls to an outlet 18 and further through channels 19 and 640. The paring disc may be provided with any arbitrary number of such chambers 42c and chambers for the balls In order that a hom ogenized product shallremain stable, it is very important that; the smaller units formed by division of larger particles or Y i'dro'ps rammyeome: into:::intimate contact with "physical equalization .upon whichthe stability depends.. But it is nevertheless very important .;that the'different parts of the treatedliquid are rapidly and intimately mixed with one another --and that the contact between the membranes :of thedrops or particles and the liquid in-which they-are dispersed becomes'asgood as" possible. -:Accordingto the invention, the homogenized liquid. may for this purpose be subjectedto a stabilizing after-treatment following immediately upon thehomogenization. It consists substantially ofan intense agitationof the various parts -of the:liquid. This. efiectmay be brought about by awhirl chamber of the same type as that used for the homogenization. A device for thispurpose is. illustratedin Fig. 9. The homogenized liquid issuing from the outlet 64, 25 or 34 of Figs. 1, 2 and 3, respectively, is conducted tQ-aninlet 8 of-the stabilizing device of Fig. 9. From this the liquid-flows through a nozzle 8|, the throughflow area .of which may :be regulated, into a cwhirlchamber 82 and .then through; an outlet 83. positioned close to the nozzle 8| and through which the liquid leaves the apparatus. The throughflow area of thenozzle 8! may be regulated by a spindle 85 with a tapered end arranged to be moved axially by a wheel 86 so as tomake it 'flll. up. the opening of the nozzle 8|-more or less. This after-treatment generally requires a pressure of only a few kilograms, whereas up to 13' kilogramsarerequired in the homogenizing paring disc. a

' Regarding the cyclone shown in Fig. 6, the slot- "shaped inlet openingmay be directed forward right against the direction of flow of the rotating liquid. Experiments have shown, however, that "a' better. result is sometimes attained when the inlet'opening has another direction, for example. is directed backward or at. right angles to the direction offlow or at a suitable obtuseor acute angle to the direction of flow. 'It may also be desirable to arrange the orifice of this inlet in a projection, or the like, of the paring disc itself. :In this way, an overlapping of the'paring disc proper is avoided, so that the friction between 'the parin'g device and the rotating liquid is re- .fduced.

'It'will beunderstood that thehomogenizer 44, Mafflb or 15, as illustrated in Figs. 1, 2, 4, 5, '7

.and-B, is formed in effect by the respective paring dis'csfthe' outer parts (4!, 49, etc.) of which form the'paring member whereby the liquid is withdrawn in a jet from the rotating. liquid annulus in the rotor and passes under pressure to thehoifr og'enizer.

a 1. An homogenizing device comprising a hollow rotor having. an inlet for the liquid to be 'homogeni zed, means in the rotor for causing the liquid therein. to partake of the rotation of the rotor, whereby the liquid forms an annulus in fthe rotor, aparing member having an inlet open- "ing positioned-to project into the inner surface of said annulus and also having a discharge chan- .nel extending through said member, and an homogenizer communicating with the inlet opening of the paring member and situated in said discharge. channel to receive liquid pared from saidannulua "'2. A.-.devic e according to.claim= l, in which the :homogenizer? forms a whirl chamber:- communicating with said inlet opening for-receiving-a liquid jet therefrom, the whirl chamberbeing open at one end to receive said :jet and discharge theliquid from the chamber, the other end of the chamberbeing closed, whereby the liquidifrom said jet is deflected aboutlBO? in the: chamber.

3.. An homogenizing device comprising a' hollowrotor having'an inlet for the liquid to'be homogenizeobmeans in the rotor. for causing the liquid therein to partake of the. rotationofthe rotor, whereby the liquid forms an annulusin the rotor, a paring member having aninlet opening positioned to project intothe inner. surface of' said annulus, and anhomogenizer forming a whirlchamber communicating with sald inlet opening for. receiving )a liquid jet therefrom, the paringmemberhaving a cyclone chamber affording .communication from said inlet opening to.v the whirl chamber, saidinlet opening being disposed generally tangentially. relative. to the cyclone chamber;

4. A device according to claim 3, in which the paring memberincludes a nipplecontaining said cyclone chamber and inlet opening and projecting outside the main portion of saidmembenso as to extend into the liquid annulus.

5. A device according to claim 3, in which [the homogenizer is formed by the paringmember, said whirl and cyclone chambers being disposed in the outer part of the paring member andhaving a common axis of symmetry extending substantially. radially of the rotor.

6. A device according to claimB, in which the homogenizer. is. formed bythe paring member, said whirlandcyclone chambers being disposed in the outer part of the paring member. and having a common axis of. symmetry extending substantially parallelto the rotor axis.

7. A device accordingto claim 3, in which the paringmember is circular and has a peripheral segment formingthe cyclone chamber and inlet opening, the whirl chamber being located between said segment and the. rotation axis of the rotor.

8. An homogenizing device comprising a hollow rotor having an inlet for the liquid to be homogenized, means in the rotor forcausing the liquid therein to partake of therotation of the :rotor, whereby'the liquid forms an annulus in the rotor, a paring member having an inlet opening positioned to project into the inner surface, the paring member having an homogenizing chamber communicating with said opening to receive liquid therefrom, anda series of balls filling said chamber to'form" constricted .passages -'for the liquid.

9. A device according to claim 8, in which the paring member forms a cyclone chamber having its rotation axis disposed'generally' radially of the rotor, said inlet openingextendinginto the cyclone chamber substantially tangentially thereof, the cyclone chamber extending from the outer part of the paring 'member. to the homogenizing chamber.

10. A device according to claim 8, .in which the paring member forms a cyclone chamber having its rotation axis disposed generally. radially of the rotor, said inlet opening. extending into the cyclone chamber substantially tangentially thereof, the cyclone chamber extending. from the .outer part of a the paring member to the homogenizing chamber, the homogenizing chamber being cylindrical and having axis substantially parallel with. said rotation axis ofithe; cyclone chamber, the homogenizing chamber having a wall projecting into the cyclone chamber and provided with a peripheral slot connecting said chambers. v

11. A device according to claim 8, in which the paring member form a cyclone chamber having its rotation axis disposed generally radially of the rotor, said inlet opening extending into the cyclone chamber substantially tangentially thereof, the cyclone chamber extending from the outer part of the paring member to the homogenizing chamber, the homogenizing chamber being cylindrical and having its axis substantially parallel with said rotation axis of the cyclone chamber, the homogenizing chamber having a wall projecting into the cyclone chamber and provided with a peripheral slot connecting said chambers, the homogenizing chamber also having an outlet opening in a wall thereof nearest the rotor axis.

. 12. An homogenizing device comprising a hollow rotor having an inlet for. the liquid to be homogenized, meansin the rotor for causing the liquid thereinto partake of the rotation of the rotor, whereby the liquid forms an annulus in the rotor, a. paring member having an inlet opening positioned to project into the inner surface of said annulus, the rotor having a centrifugal separating chamber and also a paring chamber containing said member, there being a passage in the rotor leading from the inner portion of the separating chamber to the paring chamber for conducting thereto a lighter separated component, and an homogenizer supported in the rotor and communicating with said inlet open ing for receiving liquid therefrom.

13. A device according'to claim 12, in which the paring member has a recycling passage leading from the homogenizer and communicating with the separating chamber for returning homogenized liquid thereto.

14. A device according to claim 12, in which the rotor has an outlet communicating with the outer portion of the separating chamber for discharging a heavier separated component, the rotor also having a purifying chamber through which the heavier component passes on its way to said outlet, and a set of conical discs in said purifying chamber.

15. A device according to claim 12, in which the rotor has an outlet communicating with the outer portion of the separating chamber for discharging a heavier separated component, the rotor also having a purifying chamber through which the heavier component passes on its way to said outlet, a set of conical discs in said purifying chamber, the rotor also having a second paring chamber and a, passage outside the first paring chamber for leading the heavier component from the purifying chamber to the second paring chamber, and a second paring member in said last paring chamber for discharging liquid therefrom through said outlet, the second paring member being of smaller diameter than said first member.

16. An homogenizing device comprising a hollow rotor having a centrifugal separating chamber and also having a paring chamber communicating with said first chamber for receiving a separated liquid component therefrom, a feed pipe leading into the rotor for supplying liquid to the separating chamber, a paring member in the paring chamber having an inlet opening positioned to extend into the inner surface of a rotating liquid annulus in the paring chamber, an homogenizer supported by the paring member and having a discharge passage leading from the rotor, and a return pipe outside the rotor for connecting said discharge passage to the feed pipe, whereby liquid from the homogenizer is recycled to the separating chamber.

1'7. A device according to claim 16, comprising also a branch pipe leading from said return pipe to withdraw liquid therefrom, and a valve in the said branch pipe for regulating the amount of said withdrawal.

18. A device according to claim 16, in which the rotor also has an outlet for a heavier component separated in said separating chamber, the rotor also having a purifying chamber affording communication between the outer portion of the separating chamber and said outlet, a set of conical discs in said purifying chamber, a fixed discharge pipe leading from the outlet for said heavier component, and a central tube in the rotor connecting said purifying chamber with the fixed pipe through said outlet.

19. A device according to claim 16, in which the rotor also has an outlet for a heavier component separated in said separating chamber, the rotor also having a purifying chamber affording communication between the outer portion of the separatingchamber and said outlet, a set of conical discs in said purifying chamber, a, fixed discharge pipe leading from the outlet for said heavier component, a central tube in the rotor connecting said purifying chamber with the fixed pipe through said outlet, a packing collar making a tight joint between the central tube and said fixed discharge pipe, and a pump wheel on the central tube for generating an increased pressure in the fixed discharge pipe.

20. A device according to claim 1, in which the device has an outlet leading from the homogenizer, a stabilizing device communicating with the outlet and including a whirl chamber, and an adjustablenozzle controlling fiow of homogenized liquid through said last chamber.

ALFRED GERHARD BORCK.

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

UNITED STATES PATENTS Number Name Date 1,540,592 Best June 2, 1925 1,842,877 Mulleret al. Jan. 26, 1932 1,848,531 Lamb et al. Mar. 8, 1932 1,866,638 Fawcett July 12, 1932 2,171,136 Bergner Aug. 29, 1939 2,271,982 Van Kreveld Feb. 3, 1942 2,318,293 Cornell 1 May 4, 1943 FOREIGN PATENTS Number Country Date 539,016 France June v19, 1922

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