US2435117A - Post-mixed blowpipe for thermochemically removing surfaces of metal bodies - Google Patents

Description

Jan. 27, 1948. R. s. BABCOCK POST-MIXED BLOWPIPE FOR THERMOCHEMICALLY REMOVING SURFACES OF METAL BODIES Filed Feb 13 1943 2 Sheets-Sheet 1 INVENTOR K C O C B A B Q... R E w ATTORNEY Jan. 27, 1948. s. B COCK 2,435,117

POSTMIXED WPIPE R THERMOCHEMICALLY REMOVING SURF 5 OF METAL BODIES Filed 15, 1945 2 Sheets-Sheet 2 M 551 n v i;

lmlniml 7 9 INV OR ROGER s. BABCOCK ATTORNEY Patented Jan. 27, 1948 POST-MIXED BLOWPIPE FOR THERMO- CHEMICALLY REMOVING SURFACES OF METAL BODIES Roger S. Babcock, Plainfield, N. J., assignor to Union Carbide and Carbon Corporation, a. corporation of New York Application February 13, i943, Serial No. 475,712

8 Claims.

This invention relates to apparatus for conditioning the surface of metal bodies, and more particularly to blowpipe apparatus for thermochemically removing metal from a ferrous metal body, such as a billet, bloom, slab, bar or the like.

In the casting of steel ingots and duringthe hot rolling of steel, defects, such as scale, cracks, seams, slag inclusions and the like form on and in the surfaces of the steel bodies and cause imperfections in the finished rolled products unless removed. In order to reduce the number of rejections of finished rolled products, such surface defects are generally removed before or during the intermediate stage of the rolling. Scale is commonly removed by pickling and other defects have often been removed by mechanically cutting or chipping away the defective surface metal. Hand operated blowpipes, commonly referred to as hand deseaming blowpipes, are now also used for thermochemically removing the defective surface metal adjacent each defect by effecting the combustion of the ferrous metal with oxygen. Recently, machines employing suitable blowpipe means have come into use for thermochemically conditioning the surfaces of billets and the like. Such machines may be used for conditioning steel shapes, either whencold or while they are at a rolling temperature and are passing from one roll stand to another in a steel mill.

Heretofore, an outstanding drawback to conditioning or desurfacing ferrous metal thermochemically with oxygen was the ever present danger of flashback in the oxy-acetylene premixing apparatus. A great deal of time and effort has been expended in improving mixers, mixed gas passages and nozzles to reduce such tendency toward flashback. Post mixing the preheat oxygen and acetylene at the face of heating heads, tips and nozzles, as disclosed and claimed in the copending application of Barnes et a1., Serial No. 326,880, filed March 30, 1940, for Blowpipe apparatus (now Patent 2,356,196,

dated August 22, 194 produces an externallymixed flame which is inherently free from flashback tendencies.

The main objects of the present invention, therefore, are to provide: improved apparatus for conditioning the surfaces of metal bodies which utilizes postmixed preheating flames which are entirely free of the danger of flashback; a post-mixed nozzle for deseaming or cutting, that is simple and economical in its parts, and which may be readily made from available parts and easily incorporated in standard deseaming or de- 2 surfacing apparatus; a post-mixed blowpipe nozzle that is effective and efiicient in operation; a nozzle for thermochemically removing ferrous metal, having means for producing post-mixed preheat flames which do not interfere with the oxidizing gas flow; and an improved method of removing metal from a ferrous metal body.

The present invention provides blowpipe or torch means for thermally conditioning or scarfing the surface of a steel body such as a bloom or slab, or for eliminating scale, and more particularly, blowpipe means suitable for use in a machine for thermochemically removing a layer of surface metal from the body, preferably while such body is at an elevated temperature. A multiple nozzle head discharging high temperature externally mixed preheating flames and a composite substantially sheet-like stream of oxidizing gas, is moved'relatively along the body andis maintained in contact with the work surface thereof during such movement in order that a substantially uniform depth of metal may be removed andthe gases efficiently used.

The invention also provides a hand deseaming blowpipe provided with a post-mixed blowpipe nozzle which is adapted to discharge a stream of oxidizing gas and a plurality of relatively hard post-mixed preheating flames around the oxidizing gas stream, the arrangement being such that the post-mixed preheating flames do not interfere with the operation of the oxidizing gas stream.

More particularly, according to the invention, there is provided a post-mixed blowpipe nozzle consisting of a generally tubular body having a right end face and a central oxidizing gas passage terminating in an orifice in the end face, the body also having a plurality of preheat oxygen passages arranged around the longitudinal axis of the oxidizing gas passage in substantially parallel relation thereto, and an inclined preheat acetylene passage for each preheat oxygen passage, each pair of preheat oxygen and acetylene passages terminating in a common port in the end face. The preheat oxygen and acetylene passages of each port are preferably arranged in a common radial plane extending from the longitudinal axis of the oxidizing gas passage, with the acetylene passage on that side of the oxygen passage opposite to the oxidizing gas passage, and the included angle between each preheat oxygen passage and its acetylene passage preferably of the order of 20 degrees. The inlet ends of the acetylene passages open to the annular outer wall of the body, and are supplied with acetylene through an annular chamber within a jacket mounted on the nozzle body.

Further, according to the invention, there is provided a method of removing metal from a ferrous metal body, which comprises applying at least one stream of oxidizinggas against :said body fortherinochemical reaction with themetal to be removed, while also applying a concentric series of relatively hard entirely separate pos'tmixed preheating flames against such body around said stream, said flameslbeingeach composed of rapidly merging streams of oxygen and acetylene.

Referring to the drawings: Fig. 1 is a view partly in side elevation and partly in vertical cross section of desurfacing apparatus exemplifying the invention;

Fig. 2 is a front elevational view of the apparatus shown in Fig. l; Fig. .3.is a view in side elevation of a deseamingblowp'ipe exemplifying the invention; Fig. 4 is .an enlarged fragmentary view arranged in vertical cross section of the forward end of theiblowpipe shown inFig.'3;

Fig. 5 is a cross-sectional view taken on line "5-5 of Fig. 4;

Fig.6 'is an end view taken on line B'B of'Fig.

4; and

Fig. 7 is an enlarged detail view in longitudinal section of the preheat acetylenesupply jacket. 'The desurfacing apparatus shown in-Figs. l and especially when the conditioning'head is adapted for 'desurfacing'a ferrous metal body, such as "that shown and described'in patent application of Kller et a1. Serial No. 334,510, filed May 11, i940, 'now'Patent 2,312,418 dated March'2, 1943. Such mechanism preferably "includes means for moving the desurfacing head H1 in a direction to- 'ward and away from the'body priorto and after .a surface removing operation, while'the body'is propelled'longitudinally with thehead 'Hlheld in contact with the surface thereof duringthe surface removing operation. If desired, the body may be stationary and 'thehe'ad IU'may be propelled along the body. "In any case, relative movement is provided between the'body and the head I in such .a direction as ito remove successive portions of surface metal from thebody. The head I0 is shown in position for desurfacing the bottom surface of a bodywhi chis'supported and propelled'inthe direction of its length. The

number of heads employed depends 'upon the width ofthe surface to be conditioned.

The blowpipehead [0 includes 'a'nozzle'retain- "ing'member'o'r block .II and aremovabl'e nozzle protecting shoe l2. Thehead l'fl'isirem'ovably attached to a carrieriplate 'by'thread'ed'studs l3. :Within the block ll there are a plurality of similaroxidizing 'gas "passages M each of which terminates in an enlarged 'and'partlythreaded recess l at its-forward outlet end,to operatively receive 'the inlet end of'anozzle l6 removably secured therein byan externally threadednozzle retaining nut ll. Theinlet endof each'passage M communicates with'achamber 18 formalin the block H, there being-a 'chamberlil'foreachtwo passagesi-. The inlet-end of each'chamber I8 is adapted to receive the "threaded'end or'con- 'nection. IQ ofan'oxidizing gas supply tubewhicn linturn communicates'with a suitable source of oxidizing, gas.- 'ITheioxidizingtgasilowsffrom each supply tube, through the distributing chamber l8,

the two oxidizing gas passages l4, and through the central oxidizing gas passages 20 of a corresponding pair of nozzles I6 secured in the block I l. The passage 20 may be formed as shown and claimed by the application of Arthur P. Scheller, Serial No. 322,965, filediMarch 8, 1940, for Method 'andapparatu's for desurfacing metal, now Patent 2,353,318, dated. July 18, 1944.

The outlet end of each passage I4 is formed to provide a pair of seats which coact with seating surfaceson the inlet end of the nozzle IE to form :gas-tightseals'at 2i and 22. Between these seating surfaces, the inner end portion of the nozzle 1B is formed smaller in diameter to provide a pre'heat'oxygen distributing chamber 23 for supplying the preheat oxygen to longitudinal Preheat passages in the nozzle. Preheat oxygen is delivered to each of the chambers 23 by a passage 24 within the block H,-there being an inlet connection 25 for each pair of passages 24. Preheat acetylene is delivered to each Of'the nozzles l6 by means including an adaptor plate 26 and a ,pipeil for each'blowpipe. The adaptor plate 26 isfsecure'd'in place on the block H by screws'28, assisted by screws 29 which secure the shoe l2 to the block l l ,gaskets '3fl'and3l being disposed between the'block 'I l 'and plate 26, andbetween the plate 26 and shoe l2,respectively. The adaptor plate '26 is provided with a "series "of parallel shoe l-2.

i'acetylene passages '32,there "being "an acetylene passagefor each nozzlelfi, and an acetylene inlet connection 33 for each passage 32. Each nozzle is'provided with an acetylene supply jacket 34 "having an "annular shoulder '36 constituting a bearing for the inner end of a c'ornpressi'on'spring 31, the-outer end of which bears'against a rubber ring "'3flwhich'prevents any leakage of cooling 'fiuid "froma chamber 39 in the shoe -l2. The spring "31 thus functions to help hold the nozzle 16 in'place withrespect to theblock H, and also to hold the ring 38 'in'place'with respect to the Any sulitable cooling fluid, such as water, is'circulated through'the chamber 33 by means including asupply pipe 40. The acetylene *supplyjpipesz'l within the cooling fluid chamber -39 areconnectedtothe adaptor plate 26 by glands E4|,'so that preheat acetylene is-conductedfrom each of the passages 32 'with'in'the plate 'to "a jacket 34'of a nozzle 15. The internal construction of the nozzles, with respect to thepreheat oxygen and" acetylene passages, will be described in detail "below in connection'with-Figs. 3 to 7.

The nozzles l6 in*the 'bl'owpipe head 10 are so spaced that the sides of the individual scarring oxygen streams from the central passages 20 merge so as-to direct "a substantially sheet-like *streamofcxygen onto the surface of'the work. A hearing surface -42 "of the 'shoe contacts the work and is therefore subject 'to damage by abrasion, and, to protect thesho'e l2 a layer of metal, which is resistant to abrasion at high temperatures, is-preferably deposited, as at 43 on-the -work contacting surface of the shoe i2. A portion- 44 ofthe shoe-l2 overlaps the'uppercorner of the block I I, so that any force or shock onthe shoe is taken by the block II, and the shoe cannot-shiftand 'damage the nozzles IE or break or strain tl'ie screws- 29.

Cooling water inlet and outlet connections are provided, one ofyirhieh .is shown at 45, for circu- 'lating" the cooling water through a passage "46 in the'block-I'L'a well asthrough the'pass'age 39 'inthe'shoei [2, to preventithe head from overheating in operation.

Referring to Figs."3to"7, inclusive, a 'deseaming blowpipe B is provided, which includes a gas inlet valve body 5!] having an oxygen inlet connection 5i and an acetylene inlet connection 52. The oxygen inlet connection 5! is connected to a suitable source of oxygen by means including a hose 53, while the acetylene inlet connection 52 is connected to a suitable source of acetylene through an auxiliary acetylene needle valve 5 3 and a hose 55. The conventional acetylene valve 56 of the blowpipe B, which normally controls the flow of preheat acetylene to a mixer within the blowpipe, is closed, or may be omitted entirely, if desired. A passage within the valve body 50 conducts the acetylene from the inlet connection 52 to an acetylene pipe 5! which is connected at one end to the body 50 and at the other to the jacket 58 surrounding the outer end portion of a nozzle body 59. An auxiliary acetylene passage is drilled through the body 50 so that the acetylene by-passes the valve 56, and is controlled by the auxiliary valve 54, thus a conventional type of blowpipe may be converted for use with the post-mixed nozzle of the present invention. Part of the oxygen delivered to the Valve body 50 is conducted through a preheat oxygen passage controlled by a needle valve 60 to a pipe 6! which is connected at one end to the valve body 50 and at the other end to a head 52. A preheat oxygen passage 53 in the head 62 conducts the preheat oxygen to an annular distributing passage 54 between the head 62 and the inner end of the nozzle N. The remainder of the oxygen delivered to the blowpipe B through the inlet connection 5| is conducted through another passage in the valve body 50, which passage is provided with a cutting oxygen valve controlled by a lever 55, to an oxidizing or cutting gas pipe 56, the inner end of which is connected to the valve body 50 and theouter end of which is connected to the head 52. Thus, when the lever 55 is manipulated to open the cutting oxygen valve, oxidizing gas is delivered to the head 62 having a passage 61 therein for conducting such oxidizing gas to the inlet end 68 of a central oxidizing gas passage 69 extending axially throughout the length of the nozzle body 59.

The jacket 58 and the nozzle body 59 constitute the nozzle N which is secured in place with respect to the head 62 by a screw 10 which is sleeved over the external cylindrical surface of the body 59 and is threaded into a socket ll of the head in a conventional manner, the inner annular end of the screw To engaging a shoulder 12 on the nozzle body 59 to secure the nozzle N in place with respect to the head 62. The jacket 58 is brazed or silver soldered at E3 and T4 to the nozzle body 59 which is suitably shaped to fit the jacket. The nozzle N has a fiat end face 15 provided with a central oxidizing gas orifice l5 and a plurality of preheat gas ports ll arranged in a circle about and concentric with the orifice 16. Each of the ports TI is provided with a preheat oxygen passage 18 disposed perpendicular to the end face 75, and a preheat acetylene passage 19 disposed at an acute angle to the end face 15. The longitudinal axes of each pair of preheat oxygen and acetylene passages preferably lie in a radial plane extending from the longitudinal axis of the nozzle body 59. The body 59 of the post-mixed deseaming nozzle N is preferably made by forming a series of the inclined passages l9 between the cylindrical outer surface and the end face 15 of a conventional premixed deseaming nozzle having the central oxidizing passage 69 and an annular series of preheat gas passages 18 in concentric relation with the central passage 69, the arrangement of the inclined passages 19 being such that each inclined passage has a port 11 at the end face 15 in common with the port of a preheat gas passage 18. The jacket 58 is then mounted on the cylindrical outer surface of the nozzle body 59, to provide an annular chamber 8! for supplying all of the inclined passages 19 with preheat gas, in this case acetylene. The jacket 58 also constitutes a protective ring which prevents damage to the working end of the nozzle.

As pointed out above, the conventional premixed preheat gas passages 18 in the nozzle N are used according to the present invention as preheat oxygen passages, these passages being arranged in a circle about the longitudinal axis of the oxidizing gas passage 69, while the preheat acetylene passages 19 are arranged about the preheat oxygen passages 18, the preheat oxygen and acetylene passages terminating in the common ports 11. The oxidizing gas passage 69 in the nozzle N is of conventional shape for deseaming, having an inlet portion 82 of constant diameter which i connected to a relatively long but enlarged outlet portion 83 of constant diameter by a frusto-conical portion 84. This type of oxidizing gas passage differs from that of the desurfacing nozzle l6 wherein the oxidizing gas passage 20 is of conventional shape for desurfacing, having an inlet portion of constant diameter which is connected to a relatively short but enlarged medial portion of constant diameter by a conical portion. From the medial portion said passage communicates with the orifice 20 by a gradually tapered portion which is circular at its inner end and oblong at its outer end, the Orifice being fiat or slotted, as shown in Fig. 2. Thus, a flat stream of oxidizing gas which is best suited for desurfacing is discharged by the nozzle [6, whereas a cylindrical stream of oxidizing gas which is best suited for deseaming is discharged by the nozzle N from the orifice 1B.

The preheat oxygen passes through the passages 18 of the nozzle body 59 to the end face 15 at which point it is joined by the preheat acetylene that is conveyed through the pipe 51 to the jacket 53, through the annular distribution chamber 8| between the jacket and the nozzle body, and finally out through the inclined passages 19 which coincide with the preheat oxygen passages 18 at the ports 11. The included angle between each acetylene passage 19 and its preheat oxygen passage 18 is preferably limited to a maximum value of the order of 20 degrees, the angularity between the preheat passages of each port 1'! being so limited to prevent the formation of a secondary envelope tending to burn within the oxidizing gas passage 6-9. Such an occurrence was observed when the preheat gases were reversed, that is when oxygen was supplied to the inclined passages 19 and acetylene was supplied to the perpendicular passages 18, and the angle between the preheat passages was about 60 degrees. The reason for such undesirable action is that an incomplete combustion of the gases occurs at the inner fringe of the preheat flames and the secondary envelope develops sufficient back pressure to force its way back through the oxidizing gas passage 69. By interchanging the gas connections as shown in the drawings, however, the preheat oxygen discharged by the passages 18 produces an oxygen 7 rich mixture atsthe inner fringe of;the postemixed preheat flames .so .that .nocombustible gas remains :toiburn inside the oxidizing gas passage 69. The .value of the-included angle between the preheat , gas passages 18 and 19 controls :the

.amount of deflection of the :combined lpreheat gases and thereby contributes .to .the :back ipressure-developed in the cutting oxygen passage :69. A post-mixed nozzle of the type asshown in Figs. 1 and 2, with anjincluded angle of about ,20 degrees between the outside acetylene passages and the inside oxygen passages produces no gases burning within the central oxidizing gas passage. A 20 degree angle between thepreheat gas passages 78 and .19 has been found to give the best results as a, compromisebetween asmaller angle effecting inefficient mixing of the preheat gases, keeping the flame outof the oxidizing gas passage 16 before the oxidizin .gas has been turned on, and a larger angle between the preheat gas passages resulting in .better mixingof thegases but in danger of the secondary envelope of the .flame being bent into the oxidizing ,gas passage. In .the secondary envelope hydrogen and carbonmonoxide are formed. Thepresence of these combustibles in ,theoxidizing gas passage makesthe danger of a backfire ,real when .the oxygen is turned on in thecentral. passage. Having fuel gas supplied through the inclined passages 1.9 and preheat oxygenthrough the, passages "l8 renders it less necessary tor the inclined seat between the oxygen passage 68 .and the 'distributingpassage 64 tobe gas tight,as. asmall "leakage of oxygen from one passage into the other should be harmless. The resultant ofthe preheat gases from passages 18. and '19 is inclined inwardly toward the axis of the oxidizing gas passage a less amount than the angle'between these preheat passages, inasmuch asthepassage I8 is substantially normal to; the work andparallel to the axis of the oxidizing gas passage '16. Under desurfacing conditions on hot and cold steel plate withthe post-mixedflames produced by the nozzles of thepresent.inventiomthemolten puddles produced by both types of nozzles (that is, premixed and post-mixed) with equivalent cutting oxygen passages are substantialiy similar. The invention also provides a relatively simple construction for post .mixingthe preheat gases to produce the preheat flames, withoutmaterially complicating the nozzle blocks or shoes of conventional desurfacing machines, and whichen- ,tirely.eliminates flashback troubles. 'While'the invention has been shown in connection with aa ldesurfacing head, 'Fig. 1, and a 'deseaming 'blowpipe, Fig. 3, it is to beunderstood-that-it may be used in connection with other :blowpipe apparatus and especially blowpipe apparatus "for thermochemicaily cutting, or conditioning the surfaces, of ferrous metal bodies.

-What is claimed is:

1. A post-mixed blowpipe nozzle comprising, in combination, a body having an endface and a central oxidizin gas passage terminating .in an oriflcein said end face, said body alsohaving a plurality of preheat oxygen passagesarranged around the axis of said central oxidizing gas passage in spaced relation thereto, and an inclined preheat fuel gas passage for each preheat oxygen passage, each pair ofpreheatoxygen and fuel gaspassages terminating in a commomport in said end face; and means including .a jacket mounted on said body providing a protective ring :for said body and ,:an annular, preheat :fuel

[gas supply chamber for all of the preheat .fuel gas-passages-in said body.

:2. ;A post-mixed'blowpipe .nozzle :as claimed by claim ;1,-in-which the included angle between each 'DI'EJh-Bflll oxygen passage and its 1 fuel gas passage does not exceed a value of-the order of '20 degrees.

3. A post-mixed blowpipe nozzle which .0m-

prises anoxidizing gas passage extending longitudinally the-rethrough leading to a port atthe flame end of the nozzle-a longitudinal preheat gas passage, a head secured totheend portion of the nozzle :awayfrom the flame end thereof and through which is-a passage forconnecting preheat gasto .its longitudinal passage in the nozzle, .a -jacket secured to saidnozzle adjacent theflame and forming a chambertherewith, another preheat gas. passage connected to said chamberleadingto a secondpreheat gas passage in the-flame ,endportion of said nozzle and forming an angle ,of.,about.20 withfirst mentioned preheat gas passageinthe nozzle, said nozzle havingagas port in the flame end thereof common to bothof the preheat gaspassages, the axes of said preheat gas passages intersecting adjacent the plane of the nozzle end face, and said nozzle having a plurality of other preheat gas ports symmetrically arranged withthe firstpreheat gas port around the oxidizing gas port which is larger thansaid preheat gas of-thenozzle of substantially 20 andmixing-their preheat gases-more outside than inside said nozzle,.the median of the angle between said preheat gas passages being inclined toward the axis of .said oxidizing gas passage an amount'less than theangle'between said preheating gas passages.

5. Ai-post-mixednozzlehaving a central oxidiz- :ing gas passage, a plurality of pairs of preheatgas passages surrounding said oxidizing gas passage, onepassage of .eachpair extending longitudinally of, the nozzle, the other. passage of each pair formingan angle of .substantiallyzZO degrees with the longitudinal preheat gas passage, 3, jacket surrounding said nozzle adjacent the flame end thereof, a chamber between said jacket and nozzle "to which said ,-2O degree anglegas passage is con- ;nected, the;planethrough the axes of eachpair pf preheat gas passages passing throughthe axis of the oxidizing gas passage, each pair of preheat ;-gas:passages forming a common,- port at the flame end'0f ;said nozzle.

6. A blowpipe nozzle for the thermochemical removal of metal having post-mixed preheating gas passages on at least one side of;-an oxidizing gas passage, said preheating, gas passages forming an angle between them adjacent the delivery end of thenozzleofsubstantially 20 and-mixing their preheat gasesmore outside than inside said nozzle, the median of the angle between. said preheat gas passages being inclined toward the axis ofsaid oxidizing gas passage an amount less than the angle between said preheating gas. passages, said preheat gas passages having-their axeslying in a plane through, the axis ofsaid oxidizing gaspasa e- V 7. A blowpipe nozzle for the thermochemical removal of metal having post-mixed preheating gas passages on at least one side of an oxidizing gas passage, said preheating gas passages forming an angle between them adjacent the delivery end of the nozzle of substantially 20 and mixing their preheat gases more outside than inside said nozzle, the said preheat gas passages having their axes lying in a plane through the axis of said oxidizing gas passage, at least one of said preheat gas passages having its axis substantially parallel to the axis of the oxidizing gas passage.

8. A blowpipe nozzle having a central oxidizing gas passage, a plurality of preheat gas passages surrounding said oxidizing gas passage and generally parallel thereto, a tapered end portion for reception in a tapered recess of a blowpipe head in which said nozzle is held, a jacket adjacent the flame end of said nozzle forming a gas-tight chamber between the jacket and nozzle, a preheat gas port on the flame end of said nozzle for each of said preheat ga passages, an inclined preheat gas passage within the nozzle extending between said chamber and each of said preheat gas ports, and a preheat gas passage outside the nozzle leading into said jacket chamber for supplying a preheat gas to said inclined passages.

ROGER S. BABCOCK.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 2,100,384 Deming Nov, 30, 1937 2,148,936 Geibig et al Feb. 28, 1939 1,975,029 Walker Sept, 25, 1934 2,243,184 Aronson May 27, 1941 2,210,402 Gaines Aug. 6, 1940 2,286,591 Van Triest June 16, 1942 2,356,196 Barnes Aug. 22, 1944 2,356,197 Jones Aug. 22, 1944 2,181,937 Eskridge Dec. 5, 1939 1,186,490 Smith Apr, 20, 1915 2,266,834 Walker Dec, 23, 1941 2,286,191 Aitchison et al June 16, 1942 2,335,330 Wigton Nov. 30, 1943 2,353,318 Scheller July 11, 1944 2,362,536 Bucknam Nov, 14, 1944 FOREIGN PATENTS Number Country Date 402,400 Germany Sept. 15, 1924

Images