US2436124A - Reverberatory furnace - Google Patents

Description

Feb. 17, 1948. W,F SKLENAR l 2,436,124

BEVERBERATORY FURNACE Filed Aug. 29, 1946 4 Sheets-Sheet 1 5/ lINVENTOR.

Feb. 17, 1948. w. F. SKLENAR BEVERBERTORY FURNACE Filed Aug. 29, 1946 4 Sheets-Sheet 3 IN VEN TOR.

/ZJWM Patented Feb. 17, 1948 UNITED sTATEs -wir'ENT OFFICE Wenzeslavv Frank Sklnar, Chicago, `Ill.; assi'mor of one-fourthtoJohn H. Ehardt, Chicagoflll;

vrminnie'antichi ugstzs, 1946,;A serial No. 693,688;

12 claims. (ellis-49)- 'he present'i'nventio relates to reverheiatory 'furriaces` and is particularly concerned with the provision of an improved reverberatoryffurnace Vofthe type disclosed inmy prior apilication,A Ser. No., 664,965, med Apri; 25, 1946, now Patent 2,409,810, which lis vpaiticukily adapted'to be used in melting low point metals,- such as laluminum. y 'Y One o f the objects of the inventionis-thjprovision of an improved reverberatory furnac'efor meltingmetals, which is adapted to -r'iro'du'ce a higher quality Oftmpltn, metelnaccmplish th melting in a much shorter time, with aconsider'- able reduction in the sejof iuel, a marked elimi.. nation of waste, and a 'saving in labcrhours ref quired. Another object of theinvention is the provi;- sion of an improvedmelting process-andan i rn proved process for the generation lof maiimum heat and its application to vmetal to bejr'n'olten, by means of which metal may be melted more quickly; more cleanly, vvith less lfuel and less labor than any of the devices ofthe prior art. Anotherobject of the inve'ntion is the profvision of an improved furnace which isparticil'- larly adapted to be usedfin melting valum inuni and iight alloys for die cascine, byyineans ofjwhich theseparaie furnace Usually emplyd'i'ennection with another furnace, calle'dtheholding v or maintaining `service' furr i ac e, may be eliminated and replaced "byasingle furnace from which the Vnrietal may be laled out, as" required 'foldie casting.y

Whentvvo of the furnacesmentioned are employed according to the prior'artmethodsVthey are usually red with oil f uel orby gaS .i0 n'iain v@am the casting temperature', and the metal vvhich is melted inthe separate 'furnaceis Ycai'- 'iea in potsgor males' n-th 'hidring furnace.

By providing'- my fimprovd furnace; v'p erfc' r1 n ing' both 'of these functions, lial f of the fuel previously required 71Vis saved; 'as well `,as the '-t'ime which was formerly wasted-in carrying the .metal ing, and disturbing of thev molten metall,- which causesundue `o,xridavtio,n, iszeliminated. 2;., v Another disadvantage-ofthe prior art :furnaces molten aluminum iS liable `to",bec'cintammatedby the pets, which result 'sfin dtective-castings.

Acegstrmi- 4 Another vobf'Y Vct of thevinvention. is

l5 sich of an improved jrev'erberaltoryv furnace-struc..

able and adjustable' ai" h units adapted tov be so located in thei-foft-Iie'reverberatory furnace that their effect in reile'cting and radiating heat toward the bath of metal is a maximum, and'they are also adapted to deflect, at' a multiplicity of different points, the hot combustion gases to the surfacey of the metal, `thereby causing ksuch a turbulence of the gases that a maximum engagement ofthe gasesand the mtalis accomplished, While Vstill passing the gases through the furnace in large volumeand at high velocity, and concentrating the hottest gases at the melting zone of the chamber `-to effect aquick melting.

the provi- 'ture which has'its bed andside walls so constructed that they may be used for many more vheats than 4the furnaces of the prior art, and having its roof composdvof amultiplicity' of removable and adjustable arch units,- which may be -lifteci` from Vth eir` supports .on theV side walls so that the arch units maybe repaired between :melts and so that "the restfof .tl`ie=.furriace 'lining is also available f orrepair vwhenever necessary,

Whichis requiiedonly atrlative'ly long intervals. Other f objects and advantages y of the invention will be apparent fi'oin'the following' description and the accmpanyingdrawings', iti-*which similar characters of `reife'renee indicate -si'n'iilar parts throughout the several views. f

Referring to the" drawings; l` f which thereare Fig. 1 is averti'cal 'lng''itudinal section taken through a central Vriortion or a'furnac'e embodying my invention, 'on 'the` plane-of -the line I-i of Fig.4; 1 a Y i Fig. l2 is4 asimilar fragmentary ylongitudinal section, taken onthe plane ofthe line 2"-2 of Eig-44:

Fig.l 3 is a fragmentary sectional. view, taken on the plane of the line B-"3 ofFig; 1, looking in the Fig; 4 is a horizontal'sectional -view,1taken on "theplan'e' of the line li-lofFigri; y ffFig. 5 is a fragmentary side elevational view of frig. 7is-fragmentarysetinaifview, takenn Fig. 8 isa horizontal sectieiiaI yijewpf a modireati-louent@ is prei/'lata aan 'twjsfweilsfffom dipped,4

ld either wall I2, a` curved part of the front wall I3, an`

upwardly curved'L-.rear wall I4, and the chimney wall I5.

When embodied in a stationary furnace, the rear wall I5 may be provided with an angle iron I6 welded to it and mounted upon a supporting frame member I1, having a horizontal flange I 8 under the angle iron I6, to whichV it may be welded. At the front of the furnace, that is', the Y right in Fig. 1, the bottom shell II may have a horizontal flange I9, which rests upon the horizontal flange of a front frame member 2I,f

The front and rear frame members I1 and 2| may be joined at the bottomby suitable longitudinally extendingV channelled members l1 and 2| at each cornetto form a rigid frame and base.

When embodiedin ,a-tilting furnace of the type shown in my prior application, the bottom shell II is also curvedlaterally and provided with tracks and rollers and a suitable hydraulic tilting mechanism, as described in that application; but when constructed in thestationary type, as illustrated in Figs. 1v to8-,` the bottom shell Il may be straight in a lateral direction. as shown at the bottom of Fig. '7; and its lining may be so contouredas to cause the molten metal to drain into the wells, from which it istobe dipped.

The side wallsv of the shell are-shown in Fig. 4, and they may comprisemetal plates 24.25.- The side wall 24 covers thefright side of the furnace, and is joined at theback to therear plate I5 and at the front to a front plate 426.A The shape of the side plate 24is shown in'Flg. 5. Its bottom outline isstraight.- audits rear outline is straight, forming part of the shell for the chimney and charging opening' 21, which projects upwardly above the body of the furnace.

At the roof of the furnace the two side plates 24, 25 may reach its maximumheight' at the top edge28, near the front' wall 25, .and may` thereafter be stepped downward,rterminatingat the lines 29, 30, 3I, andf32, which indicate the top wall of each side of the furnace at these points, formed in successivelylower steps.

The bottom shell II may be lined with suitnably shaped rebrick` 33 (Fig-41) which are suitably curved vto forma curved recess ,-34 on the bottom, inside ofthe furnace, `toward which the molten metal runsfrom the throat 35 of the chimney 21 as `it is melted, and the me brick 33 mayextend upwardly along the back of the chimney on the shell fparts I4, I5 and forwardly on the shell part I3.

At the rear insulating .wall 35 of the chimney 31 the nrebricks are suitably shaped to house a plurality ofiirebrick tiles 3,6,39, or metal pipes, and closed andprotectedbyzthe-tlrebrick and forming an air preheating passage, the shape.

of which is shownin Fig. V3." e

HereV indicates the outlet of a centrifugal blower, which blows air into-.the` conduit 36, the

end of which is joined at theleftto the conduit 31, which carries theair toward the right. Therev conduit 31 is.,` joined with conduit 38extending toward theleft, vWhere vit is. joined with conduit 39, carrying the air toward the right-to asuitable pipefAL-which leads forwardlyV of the furto supply them through suitable valves with preheated air. The front wall of the furnace is insulated with a suitable block or a plurality of blocks of rebrick insulation 44, which are fomncd with the outwardly tapered burner openings 45, 45, into which the burners 42, 43 project.

In the smaller embodiments of the furnace a single burner may suilice for both the melting and the maintenance o f the metal in the molten condition, in which case it-would be located like Vthe burner 43, but in the larger furnaces any number of burners may be employed, such as two, three, four, or more.

' The left metal side wall 25 at the bottom of Fig'I 4 is elongated beyond that of the other side 24 sulciently to form at the rear bottom a rectangular extension 41 (Fig. 5), which forms the side wall of a metal well 48, into which the ladles may be/dipped, and in which a. suitable supply of molten metal can be kept at all times.

- In addition to the shell portion 41, the well 48 has a rear. wall shell 49 andaright side wall shell and the bottom shell II has a rectan gular extension 5I (Fig. 2.) extending under the well 43. The well 48 is lined, adjacent the shell portion 50, with an insulating wall 52, and at lits rear wall with an insulating wall 53, and on its side, adjacent the shell portion 41, with an insulating wall 54. Y

Both of theY side walls 24, 25 -of :the shell are lined with insulating Walls. 55 and 55, respectively, which, like the vside walls 24, 25, are stepped downwardly toward the rear, as indicated in Fig.

Y 5, from 28 to 32. Thus both the side walls 24,

25 and side insulation 55, 56 step backwardly in such manner as to support a plurality of arch units, indicated at 51, 58. 59, and Ell (Fig, 3) and located successively below each other toward the rearofthefurnace. j

Such an arch unit is illustrated in Fig, 6, and each arch unit may consist of apair of end plates 5l, 62, each of which comprises an angle having a lower supporting flange 63, 64. The length of these angles'SI, 62 depends upon the front-to- Vback width of the arch, and arches may bemade of any desired-width; for example, the arch 51 comprises a three-brick arch, while the arches 58-60 are each made of one layer of rebrick. The arches in narrow furnaces may be curved as shown in my prior application, above-mentioned; but in relatively wide furnacesare preferably made straight, as shown in Fig. 6; and they include a'plurality of rebrlcks-BS, preferably of the type having tongue and groove formations of one' brick engaging those of another brick.

The end bricks 6.6 engage the end flanges'GI, 52 and rest upon the lower flanges 63, 64 of these Y angle plates. A pluralityofsteel tie, yrods 61 extend through the plates 6 I, 62 and clamp the end plates Si, 52 against the bricks 65, 66 by means of a threaded portion 58 and a nut 69. yThus the arches are adapted to be handled as a unit; and the space between the plates 6I 62 above the lirebrick 85, 68 'and surroundingv th tie rods 61 may be mieu with initially plastic insulation 1o.

` The flanges 63, 54 of each arch unit rest on top of thevwalli in this case atfthe top wall surface 25, but inothr cases atv the top'surfaces 3Il-32.

The arch units are preferably 'provided with means for attachment to a hoist tofacilitate theirl handling, which in the case of narrow arch units 58-50 may consist of a pair ofl U.shaped steel Ufr'is) these U-.Sbapesi reds. leerme their 71ml Y amount. ,as regulated by the valveand Withair in suitable amount, as regulated by the valve, the air having been preheated by being passed through the conduits located around the uptake of the furnace, after the furnace itself has rst been subjected to a period of preheating by means of the burner, with the uptake grille closed.

The flame from the burner is directeddown-- The hot gases which are deflected downwardly toward the metal surface 16 are again reflected upwardly into engagement with the abrupt shoulder 14 of the arch unit 59, where they are again deflected downwardly by the abrupt surface 15.

The free surface of the metal again -reects the the furnace, and thence laterally from the chamber 81 into the chamber 88, and Well 48. Y

down toward the The burner 43 divides its ilamesbetween .the

melting'chamber 81 and the melt -maintenance' chamber 88, and sufcient ofthe name and combustion gases pass down through the cham-. ber 88 and out of the grating overthe well to maintain the molten metal in'proper molten condition and at a suitable temperature.

Instead of requiring two separate furnaces, and instead of requiring the dipping and carrying of metal from the melting furnace to the vholding or maintaining furnace, a supply of molten metal is provided at all times by the well 48 for casting operations.

The amount of fuel required is greatly reduced, the cost of the installation is reduced,.ancl the unnecessary spilling, splashing, and disturbing of the molten metal, which causes undue oxida-l tion, are substantiallyeliminated.

In the embodiment of Figs.' '1 and 8 two wells are provided so that this .melting furnace provides a ready supply of metal on eachof its sides for serving two batteries of casting or die casting machines. s

The present furnace is adapted. to melt the metal required in a fraction of `thegtime required for other* furnaces, and it produces amolten metal which has far superior physical characteristics, equivalent to that produced'byyan electric -`furnace, which requires a much longer time `for `melting.

, 'I'he present furnace" may beconstr'uctedat a much lower cost than electric'fl'lrnaces, .andis 1..'I'his'furnace replaces a. melting furnace and a holding furnace, and reduces the cost of the installation.

2. Greater flexibility with perfect control.

3. -Fifty percent lower fuel consumption.

4. Seventy-five percent savings in labor cost.

I 5. Faster melting in a fraction of time required l by other furnaces, resulting in greater output with less equipment.

6. Superior metal, both chemically and physi cally.

. '7. Elimination of costly crucibles and costly and difficult furnace repairs.

8. Lower metal losses. f

While I have illustrated a'preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention. what I claim as new and desire to secure by Letters Patent of the United States is:

l. The method of preparing metal for casting operations which comprises feeding the metal continuously over a predetermined period of time into a hopper, comprising the uptake outlet of a reverberatory furnace toprovide a batch of metal of predetermined amount, the solid metal accumulating on the floor of the furnace at a restriction at the lower end of said uptake to be preheated by the passage of hot combustion gases out of the uptake, and projecting into said furnace from the opposite end an intense flame supplied with fluid fuel, and preheated air in predetermined mixture under predetermined pressure and velocity, the said flame .being directed downwardly and rearwardly toward the accumulation of solid metal at said restriction andv spreading to engage the roof of the furnace. and the bedl of metal in a concavity in the floor of the furnace and in a reservoir chamber disposed laterally of the iiame to receive a portion of the flame, theV upper combustion gases of the flame being projected against a plurality of abrupt shouldersv and deected downwardly a plurality operations which comprises feeding. the metal continuously over a predetermined period of time into a hopper, comprising the uptake outlet Iot'va reverberatory furnace to provide avbatch of metal of predetermined amount, the solid metal accumulating on the floor of the furnace at a restriction at the lower end of said uptake, to be preheatedby the passage of hot combustion gases out of the uptake, and projecting vinto said 4'furnace from the opposite end and an intense flame supplied with fluid fuel, and preheated air in predetermined mixture under predetermined pressure and velocity, the said tiamebeing directed downwardly and rearwardly toward the accumulation of solid metal at said restriction and spreading to engage the roof of the furnace and the bed of metal in a concavity in the floor of the furnace and in a reservoir chamber disposed laterally of the llame toreceive a portion of the flame; the luppercc'imbustion gases of the flamebeingA projectedy against' a plurality of'V abrupt shouldersand deflectedv downwardly laplu rality of'times toward the metalv on thek iioor,v causing the-molten'metal to drain by-'gravity from the point of' melting to said reservoir, `and Vre-V stricting the flow of' gases from an upper open-- ing in saidreservcii'A toV provideisuilicient passage of hot" combustion'gases throughthereservoir vforv maintaining the molten metal in constant con-4 dition for casting operations, and interposing az barrier to the flow of metal at the; free-surface' between the point of melt'and said reservoir to i cause the metal to ow'unde'r the barrier andto effect an automatic skimming and retention of' floating impurities in* the furnaceY apart from the reservoir.

*3l A reverberatory furnace formelting rela-q tively low melting point metals Afor die casting operations and the like, comprising a metal-shell curved downwardly from` the back and the front to forma central cavity for receivingfmolten metal, said shell being provided with end walls andl side' walls and being lined on' its bottom, ends, and sides with rigid insulating material, said shell' also including at one side an' elongated melt maintenance clfiamber,` andv theiloor of said` cavity draining toward'saidmelt maintenance cham-g ber, which is providedat a predeterminedl point wit-ha dipping welllocated at the lowest point of the furnace, said furnacebeingprovided with an uptake at one endandburner means at theiotber end, and said burner means being located.` topro-j ject its flame toward thebottom ofthe uptake which-serves as a hopper for metal to be melted, and also towardsaidfdipping ywell through said melt' maintenance chamber.

` 4. A- reverberatory furnace for melting relawhich is provided at a predeter-niined point witliv a dipping well located at the lowest point of the furnace, said furnace being. Aprovided with an uptake at one end and' burner means at the other end, and said burner means beinglocated' toproject its flame toward the bottom. ofthe uptake1 which serves-asa hopper for metal to. be melted, and also toward said dipping well through said melt maintenance chambensaid uptake andfdi'pping well being both providedv with a suitable covering member and having'ports for passage of combustion gases, the ports being small enough to restrict the now of gases and 5. A reverberatory furnace for melting relatively low melting point metals for die casting operations and the like, comprising a metal shell curved downwardly from the backand the front to form a central cavity for receiving molten metal, said shell being provided with end walls and side walls and being lined on its bottom, ends, and sides with rigid insulating material, said shell also including at one side an elongated melt maintenance chamber, and the iloor of said cavity draining toward said melt maintenance chamber, which is provided at a predetermined point with a dipping well located at the lowest point of the to intensify the" furnace, said furnace being .provided with an up take at one endand ,burner means atV the otherv end; and: saidburner meansbeing located to project-its flame towardthe bottomofl the uptake which serves -as'a hopper for metal-to be melted, andl also toward e said dipping well throughv said melt maintenance chamber,` the said furnace havingitsL-roof provided with a -pluralitvoi separate, removable arch units adapted to be hoisted from the supportingwalls -tolgain' access to the interior of? the furnace for repairor replacement of its parts; t

6. A- reverberatoryl furnace for/melting rela tively low melting point metals for die casting operations`v and` the like; comprising a metal shell curved downwardly from theb'ackand the front toV lform a central f cavityf for receiving moltenl metal;` said shellvv being" provided with endv walls andside" walls andfbeingslinedy on its bottom, ends,

andsid'eswith rigid insulating material, said-shell also-:including at` one side anelongated' melt maintenancechamber, andi the iloor of said cavity draining towardvr said melt' maintenance chamber,

which isp'rovided aiya,v predeterminedy point with' a.; dipping well located at thelowest point of the furnace, said furnace being' provided with an up take at one endl-and bur-nervmeans at the other end; andis'aidburner means beinglocated to project'- lt'sa'metwa'rdf the fbottom of the uptake whichservesasba hopper-rior metal to be melted, and'. also toward' said dippingk well lthrough saidv melt maintenance chamber, the'- said melt maintenan'cel chamber being provided with a transverse insulating-1 barrierj located with its upper ledgleabove the free surface-ofthe meta1,but permitting'the'passage of flame above'said upper surface, having an aperture below the free surface of the-metal; for the passag'eiof'moltenmetal along thelloorinto thewell. I n Y vl7: A `reverberat'o'ry furnace" fr'vmeltlng relatively l'ow'melting point metals V for die casting operationsandthelike, comprising'a 'metal shell curved downwardly'froni-'the back and the front to formv av central cavity for receiving vmolten metalf said1- shell being provided with end wallsy andsidev walls andbein'g lined on its bottom, ends,

and sides with rigid insulating material, said shell also including-at one side an elongated melt maintenan'ce chamber, and the *floor of said cavity draining toward said melt' niaintenancev chamber,

which -isV provided at aj predetermined point with a" cliiplnglv wellf located@ at the lowest point of thev furnace, said furnaccbeing provided with anv up-f take at one end and'I burner7 means* at the other end; andE said burner meansbeing located to proect--itsj flame towardthefbottom of the uptake which serveslas ahopper for met-al to be melted,

and also-toward saiddipping wellthrough said' i nelt 4maintenancenliamber,` the said uptake hav conununicatmg ai passagesyand means forpro'- yelling air' through-the-lpassages'fthrough the burner means to provide a highly preheated source of air for the burner means.

8. In a reverberatory furnace, the combination of a metal shell provided with a main melting chamber and with a pair of dipping well chambers, said main melting chamber and dipping well chambers having their bottoms and side walls lined with heat-resistive, rigid insulation, and said main chamber having its iloor sloped downwardly from the front and downwardly from the back to a central cavity which drains laterally to each of said wells, a roof for said furnace resting on the side walls. and an uptake located at the rear end of said furnace, said uptake having its lower end in ,communication with the main chamber through a restricted opening and serving as a hopper for the supply of. metal to bey meltedat said restricted opening, and burner means in the s; forward end of said furnace and projecting a, name toward said charge, a part ofl said flame being deiiected into each of said dipping well chambers. Y t l 9. In a reverberatory furnace, the combination l` of a metal shell provided with a main melting chamber and with a pair of dipping well chambers, said main meltingr chamber and dipping well chambersihaving their bottoms and side walls lined y,with heatresistive, rigid insulation, l and said main chamber having its iioor sloped downwardly from lthe o front and downwardly from the back to a central cavity which drains laterally to each of said wells, a roof for saidfurnace resting on the side walls, and an up- 204 take located at the rear end of said furnace, said uptake having itslower end in communication with the main chamber'through a restricted opening and serving as a hopper for the supply of metal to be melted atsaid restricted opening, 2:5. and burner means in the'forward end ofvsaid, furnace and projecting a nametoward said charge, a partof said flame b eing deflected into each of said dipping v,well-chambers, the said roofv being provided with a plurality of separate` arch 304 units, certain Aof said arch units being stepped, downwardly `with respect to the arch unit im mediately in front ofv it, exposing apiuralityof forwardly `faceS01'the arch units as, shoulders to engage the iiame and gases and del-V, fleet them toward the bed ,of metal a plurality of times. Y Vi. 10. In a reverberatory furnace, the combination ofv a metal` shell provided with a main melt-4 ing chamber and with a pair of `dipping well o chambers, said main melting chamber and dipping well chambers having their bottoms and side wa11s lined with heet-resistive. rigid insulation, and said main chamber having its floor sloped downwardly from thefront and. down-f wardly from the Vbaci: to a central cavity ,which drains laterally tokeach of said wells, a `roof Vfor, said furnace restingon the sidewalls, and -any uptake located at the rear end V`ofls'aid furnace said uptake havingits lower end incommunia-- 5o v tion with the chamber through a restrictedl Opening and, .as a hopper for the :sllriplv` 0f metal@ .hemelted Ylist-iii restricted Opening.; and burner means 'i'n l,the-jforward end of said; furnace and projec Y, a `ilame toward said. 55 charge, a part of-.sai name being deflectedrinto each of said dippinggwell chambers, the roof of said furnacebeing-rprovidedwith means for gienesting 8,' Porti@ Pune. nmiani'gases milo the, upper part of -thedippingnwelisfor maintenance of the melt and metaltemperature therein.V Il A, 11 In a reverbsmtefrguriiecenhercmbimi2: tion of a metal shell provided with a main melting chamber and with a pair of dipping well chambers, said main melting chamber and dip-` ping well chambers having their bottoms and side walls lined with heat-resistive, rigid insulation, and said main chamber having its oor sloped downwardly from the front and downwardly from the backto a central cavity which drains laterally to each of said wells, a roof for said furnace resting on the side walls, and an uptake located at therear end of said furnace, said uptake having its lower end in communication with the main chamber through a restricted opening and serving as a hopper for the supply of metal to be melted at said restricted opening, and burner means in the forward end of said furnace and projecting a flame toward said charge, a part of said iiame being deflected into each of said dipping well chambers, the said dipping wells beingeach provided with a grating for restricting the flow of gases from them when the grating is closed, to intensify the action of heat therein.

12. In a reverberatory furnace, the combination of a metal shell provided with ya main meltting chamber and with a vpair of dipping Well chambers, said main melting chamber and dipping well chambers having their bottoms and side walls lined with heat-resistive, rigid insulation, and said main chamber having its .floor slopedl downwardly from the front and down- Wardly from the back to a central cavity which drains laterally to each of said wells, a roof for said furnace resting on the side walls, and an A uptake located at the rear end of said furnace, said uptake having its lower end in communica# tion with the main chamber through a restricted opening `and `serving as a hopper for the supply of metal'tol` be melted at said restricted opening, and burner meansinthe forward end of said furnacev and projecting a iiame toward said charge, a part oi'said flame being deiiected into each of said Vdipping well chambers, the said wellsA being separated from the main chamberby a transverse baille spaced from the floor to permit metal to flow into the wells, and spaced from theup'per part ofthe well to permit ame to bev deflected into the well above the molten metaltherein.. 'A Y l g` ,WENZESLAW FRANK SKLENAR.

n "REFERENCES CITED .Thexfollowing references are of record in the file of this patent:` Y

STATES PATENTS Number Name Date 2,264,740. e Brown Dec. 2,- 1941 j a FQREIGN PATENTS Number i Country I Date 370,636 Great Britaia..r r. apr. `14, 1932 Certificate of Correction Patent No. 2,436,124. February 17, 1948.

WENZESLAW- FRANK SKLENAR It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 1, lines 5 and 6, strike out the Words and comma now Patent 2,409,810,; and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of April, A. D. 1948.

THOMAS F. MURPHY, Assistant Commissioner of Patents.

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