US2095747A

US2095747A - Blowpipe and method of forming combustible mixtures

Info

Publication number: US2095747A
Application number: US689176A
Authority: US
Inventors: Wilgot J Jacobsson
Original assignee: Union Carbide and Carbon Corp
Current assignee: Union Carbide Corp
Priority date: 1933-09-13
Filing date: 1933-09-13
Publication date: 1937-10-12
Anticipated expiration: 1954-10-12

Description

fOct. 12, 1937. `w. J. JAcoBssoN 2,095,747.

`BLOWPIPE AND METHOD oF` `FORMING COMBUSTIBLF.: MIXTRES fFiledsept. `13, 1935 s sheets-sheet 1 rmw ' ATTORNEY Oct. `12, 1937.A w.".J.|Aco1assot\r|` $2,095,747

` BLowPIPE AND" METHOD `oFFoRrJlING CoMBU's'TBLEfMuTUREs 'Filed sept. 13, 935 l s `sheets-sheet 2 ATTORNEY Patented Oct. `l2, 1937 e Y f' v l y j l flzmssii 'a A f` y LowPlPE AND `anz'rnon or Folin/mm` l i WMPJSTmLEMIXTUBES y {.wilgotaiugooiiosoiigfunoio; N; Y., ossignof, by t "l mesne asslgnlnentsgdtolUnion Carbide and Cara bonCorporationi,alcorporation of NewYork application september 13,1933iseriaiNo6sai76f igfiaoiaims. (elise-#gul 'Ilhis invention relates# to`imp1"ovemeiits in i A further object of thisinvention is to produce blowpipes, such as are used in performing welda a flame adapted to cause the formation of ys. l ing, cutting and similar operations onmetal;` and adherentlslag when used in `.combination with an also to a method of forming combustible gas mixoxygen lstream `espeiiialli' l101 i189 1li deseaming tures of air, oxygen and a fuel gas.` or flame machining'operations. f V- u a Heretofore, the combustible mixture 'usually f The above andv other objects. andthe `novel formed in the blowpipe contained "substantially features of` thisinvention will be apparentfrom y pure oxygen and o. fuei gas. v Generally the mixthe follewingdescription arid the accompanying ture formed within the'blowplpecontained about drawings, inwhich y t i j a. i vl0` one-half of the oxygen required to combine with l Fig;y I is a top 1119.11` view l, of ya blowpipe emk10 the fuel gas andthe remainder of the oxygen bodyingthls invention;` I i a required to complete-the; combustion of the vfuel F18- 111s a rear end View 0f the blOWDiDe Shown gas was taken'from the air surrounding the name. i11`F18- I- y Such combustible mixtures produce a flame gen- F18. III` is a crossssectiQrDrOD-fline m-III in erally known as a neutral ilame. A givenfuel F18. I. l i y y '1 5 gas in `such a mixture `produces ya fixed llame Fig# IV i5 a GIOSS Section 0n line IV--IVln F18.` temperatureatitshottest portion, the portion of VIII showing the valves inthe `blowpiperear the name thatis generally applietifto` metals or body and having the 111361711022188 remOved from a the like for heating them.: It isthlsfportionof t the bOdY. y so the-flame that is referred toi where iiam'eteiri` Figs. VfVI, and VII arerespectively` cross sec- 20 peratureis mentionedfhereim Inf the use` of tional views o! the rear body .of the blowpipe fuel gases such as acetylene which produce rela- Shown f OD 111165 V--` ,VI-J-VI and VII-'Vn Off tively highl temperature fiamesydue to a high EISX'IIA:` -l ,1: p y heat of combustion, it is deslrablejtoreducethe 1 y 1*'18- i8 afragmentary bottOm View 0f the flame temperature to make the amei suitable blowpilie Iearbodywlth the S38 0nt1`01 V81V68-25 i forlwelding and/or cutting operationswhichV reremoved and Fig. 1X 1S 8 mar-view 0f the blOW- quire relatively 'low flame temperature,` Vsuch as pipe-rear body "on line IX--IX of Fis-` III ShQWra "may be produced withhydrogen; i i f ing the -hose 'line` connections and gas control Furthermore, inthwtype ofblowpipeused yalvesremoved.-

e y L" ao heretofore where ai large portion `of the oxygen X is ii` cross section of theV blowpipe' 0n i is'absorbed fromthe air from without the blow- 'line X-X in FigrIIL ShOWinEiihe blOWDiPe'head- Pipe, the fuel gas is not burnedasemciently `as Fig. `XI is a diagrammatic sketch of the blowwhen a" greater portion of thevxyzen-*ismixed pipe. Y l y A y with the fuelgas within the blowpipe. Most of the' principles involved in the method Where `attempts have been madetd increase and apparatus described herein are vapplicable 35 the `burning efilciency oi.' ythe fuel gas by into` both cuttingand welding blowpipes. `.Fortl'ie creasing the ratio ofthe oxygen tothefuel gas purposeof illustrating this invention, the method aboveuthe normal ratio in` the n1owpipe,` objecand apparatusare described inlreference to a cuttionable characteristicsfof the llame havebeen ting blOWPiDe Using- 8 10Wl VelOCitY OXYEGDJG `i0fproduced. Some oLftheseV objectionable )char- `adapted irlremviu the Surfacemealf Buch 40 y teristics are shown'by the lack" of stability `of a operations are knownasdeseaming oriamema- `the flame,'the"occurrence of flashbac]ts,` the ox" "chinin f "j f fidizing effect of the flame 'on welded'jmetal and The blowpipe comprises a handle H to which a a e'xcessiveheating of the metal in" some" welding valve bodyB is attached. Hose lines (not shown)` V45,and cuttingoperationsj l f for-'fuel gasiandacombustion supporting gas 45 i 'I'hereforeanobject of'this' invention is to prosucha's oxygen `are-connected to ,ltheyalve body vide an improved apparatus landxnethod for util- `B\ EThe Oxygeifol 61112151118 DurpOBeS is fed t0 the "izlngfa: ".ffuel gas havingfa high "heat` of" comlblowpipeheadile and controlled by a cuttingox- F bustion, such ,aslacetyiene for producing" stable ygei-i'valye Vin the usualmannen Air is mixed "o ilames havingl alhigher or lower temperature than with a portion of the oxygen supplied tothe blowthe neu 4al and havingla `high resistance pipe and thenafuel gas is'` mixed with the air and to flashbacks. J a v, "oxygen-mixtureto produce a. combustiblegas l Another objectiof this inyention is I"to reduce mixture suitable forproducing a heating flame. the consumption of fuelgas and to stabilize the 'ihe oxygen and fuel gas employed to Produ@ S 5me, f :the-commis blegasfmixture may be turned-ong;

hose nipple I 5 which is connected to a pipe fltting I6 by a union nut I8. Ihe pipe iltting Il is screwed into a valve chamber I1 formed in the and lisscrewed on the bushing 28. The valve V f valve body B which receives the oxygen from the ntting I8. The cutting oxygen is controlled by the cutting oxygen valve V having a seat I8 held` in place by an externally threaded locking ring I8 screwed into the valve chamber up against the v,valve seat. A valve stem bushing 28 is threaded into the end oi' the valve I1'on the outlet side 2|. A central bore 22 is formed yinthe bushing 28 through which the valve stem 23 passes. A packingnut 24 reoeivesfthe stem 23 is retained on its seat I8 by means of a valve Jspring'25'which is compressed between the pipe tting I8 and a valve spider 28 which centersthe valve inthe chamber.` '111e cutting oxygen valve ,V m'aybe operated by means 'of a lever 21 which isactuated by an externally extending `button 28. 'Ihe lever 21 isvpivoted on a pin 28 in a block 80 in the blowpipehandle H. The lever 21 actuates a plunger 3| which in turn actuates the valve stem 28 and the cutting oxygen valve V.

Upon pressing the cutting oxygen valve button 28, the oxygen passes through the valve seat I8 and into the outlet 2| of the valve chamber I1. Asshown in Fig. VIIa transverse bore 82 conducts the cutting oxygen from the valve outlet 2| to a longitudinal bore 88 in thevalve body B to which a tube 84 is connectedwhich conducts the engen to the blowpipe head He. The cutting oxygen tube I4 is soldered or otherwise connected to abore 85 in the blowpipe head. 'Ihe bore 85 in the head H' is pierced by a transverse threaded "bore Il int'whlch aV constrlcting plug 31 is vvwhich communicates with thecavity 88 in .the

head -H and-conductsthe` oxygen to the disv charge orifice 42 in the nozzle 88.

' The heating or preheatingsoxygen to be combined' with the fuel gas to' form the combustible gas mixture is taken from the inlet to the cutting oxygen valve I1 in the'valve'block B through a transverse .bore 48 controlled by a stop valve 44 l "located-therein whichl is operated by a valve knob 44l as shownfinFig. IV. The oxygen may pass through the valve seat 45 to a passage 48 leadingl to the inlet 41 of the oxygen valve 48 in the gas isaver S. When the gas saver valve 48 is opened y'outlet 48 of the valve and then to a passage" "leading to an airoxygenmixer ileformixingair with' the oxygen as shown in-Figs. IV andVI. 'Ihe voxygen enters the bore 52 in the air-ongen fmixer 5I which is closed by a screw plug. threaded into'theend of the mixer bore. 'Ihe oxygen passes through an injector .nozzle 54 gen vthrough the discharge orltlce of the nozzle 54, air is drawn or aspirated into the oxygen stream from an annular chamber 51 around the nozzle, which is supplied with air from the atmosphere by means of a bore 56. 'I'he entrance of air bore 58 is protected by a shield 58 which may be made in the form of a meshed screen to prevent the bore from being plugged with dirt or by the operators hand. Clearly p the rate at which air is aspirated by the oxygen which the injector nozzle 54 projects will be substantially proportional to the rate of oxygen projection.

v VSince rthe oxygen valve 48 of the gas saver valve arrangement is either fully opened or entirely closed it follows that the stop valve 44 controls the rate of ilow of the air-oxygen mixture and provides in one form means for keeping constant the rate vof ow of the air-oxygen mixture. The

mixture of air and oxygen is conducted through a throat, 58 to a tube 88 which is connected to said throat. The air-oxygen tube 88 extends to the head H of the'blowpipe and is connected -to a chambertherein including a transversefbore 8| in the blowpipe head. A return tube 62 for the air and` omgen is connected at one end to the transverse bore 6I ink the ,blowpipe head He and at the other end to a -bore 68 inthe valve body B as shown in Fig. V. 'I'he bore68 and a transverse bore 68* connect the return tube-62 to the rear end of the bore 64 of a mixer 65 for mixing a fuel gas with the air'and oxygen. The rear end of bore 64 of the air-oxygen-fuel gas'mixer 85 is closed by a threaded plug y66 screwed into the outer end-of the mixer bore. A mixer nozzle 61 is secured in the mixer bore 84 by means of an externally threaded locking ring 88.

The fuel gas to be mixed with the air and oxygen in the air-oxygen-fuel gas mixer 85 is conducted to the blowpipe through a. hose (not shown) which maybe connected to a hose nipple 69, secured to a fuel "gas control valve body 18 byv means of a union nut 1I. A passagel extends through the fuel gas valve body 10 and a vvalve 12 operated by a knob 12Il is located therein to control the ilow of the gas from the valve inlet 10b to its outlet 10c. The valve body 18 is screwed into a bore 13 in the valve body B lattached to the rear end of the handle H so that the valve outlet 1I!c is connected toa chamber 13%* in the valve body B. A passage v14 in the valve body B connects the chamber 13* to the inlet chamber 15 ofthe fuel gasvvalve 16 of thegas saver S. A metering plug 11 is screwed into the outlet from the valve 18 Vandthe plug 11 is provided witha central bore which delivers the fuel gas to a passage 18 leading to the air-oxygen-fuel gas mixer 85. Different metering plugs may bev made with bores of different size and they may be made in- Aterchangeablewith each other to secure the desired proportion 'of fuel gas in the combustible mixturek as will be'hereinafter explained. lWhen A the

gas saver valves

48 and 18 areopenth'e mixture of and oxygen is discharged through the air-Oxygen-fuel gas mixer nozzle 61 andV mixes with the fuel gas atthe end of the nozzle. Preferably the air-oxygen-mixture is given a greater velocity than the fuel gas to suck the fuel gas into ythe air-oxygen stream. The combustible mixture formed by the'mixing of the air and loxygen Yand the fuel gas are conducted to a chamber 18 in theheadv H of the blowpipe by means of a tube 88 which is connected at one end to the expansion chamber 8| leading from the throat B2 of the air-oxygen-kfuel gas mixer 65 andV at the otherend to the blowpipe head H". The combustible mixtureA passes through longitudinal gas mixture passages 90 in the blowpipe nozzle-30 and may be ignitedat thedischargeend of the nozzle i by means oftheupilot light burner P, which will be `hereinafter described.

The` length and volume of the conduit `60,02A

between the'air-oxygen mixer 5| and the airoxygen-fuel gas mixer 05 is constructed in accord--` ance with the principles set forth in my copending application Serial No. 631,288, med-August 31,

. 1932, entitled Blowpipes and a method of preventing `flashbacks therein. Briefly, the` section ofr the heating oxygen tube between the end of the injector nozzle 54 of the air-oxygen mixer, 5| and the end of the` nozzle 01 of air-oxygen-fuel gas mixer 65 is constructed to permit-the free passage of gases .from the mixer throat .82" of the latter mixer backward into, said sectioneof the heating oxygen tube when abackfire occurs in the mixing tube 00. lior` `the `purpose of `preventing flash-` backs, a minimum length-.and volume ofv this section of the heating oxygen tube for a given length l and vo1ume of the mixing tube 00, 0|, '82, 90.r yeli-- tending from the `end of the air-oxygen-fuel gasY mixer Vnozzle 91g to the `end of themain burner nozzle isrequired. i Within limits, the mini- `mumlength and volume ofthe section of the heating oxygen tube varies inversely as the length and volume of the mixing tube. 'Ihe `air-oxygenmixer 5| isplaced at such appoint in the heating oxygen tube that the backiiring gases that may be forced backward into this" tube willbe cornpletely burned out or extinguished before reach'f ing the mixer 5| and thus prevent any lflame from escaping through the air inlet 56. i. f.

The gas` saver valves40and I0 ar the dia?" phragm type and they are secured `into" cavities 9| in the rear valve .bodyB by meansvof `hollownuts` 92 which are screwed intothel cavities 9|.` The nuts v92 clamp the diaphragm valves 40 vand 16 between the end of the nuts 92 and thebottom of the cavities 9|. The diaphragm valves 49 and `1li are normally retained ontheir seats 93 by means of1springs'94 compressed between the outer end of the hollow nuts 92 and a shoulder onthe `valve stems 95 of each of the diaphragmfvalves 48`and 16. Each of the valve stems 951s attached atone end to its corresponding `valve andthe othery end of each stem extends through its corresponding hollow nut 92.l Thegas savergvalvesl 40 vand 16 are operated by means `oi' a single lever98 which ispivoted on a pin91 mounted in arms 90 on the` valve bodyB. Theouterends of the .valve `stems 95 are provided with necks 99. The rear arm 09* of the` LS saver lever 9| fits around the necks 99 and is adapted to contact with the stem heads |00` at theouter end ot the'necks 99 to operate `the valves Q48 and `"I6 in oppositionto the springs 94. The gas saver lever 0I is cut away next to head |00 ofthe stem of the fuel gas valve 16 so that the lever will strike thehead |00 of the oxygen valve 40 beforeltstrikes the head |00 of the fuel gas valve 10 and thereby cause the oxygen valve 4l to open sooner than and close laterthan the fuel gasvalve 18. This construction of the gas saver S turns the oXygenon beforethe fuelgas is turned on and thereby creates a Ksuction in the air-oxygen-fuel gas mixer 0I before the fuel gas reaches that point and thereby prevents the fuel gas from escaping through the air inlet 56 in the air-oxygen mixer or beingemixed with the air and .oxygen at a point in rear` of the mixer nozzle 61.

The pilot light `burner P is supplied with fuel gas through a passage |0| in the rear valve body B, ,which brancheson from `the passage 14 leading to the fuel gas savervalve `1l as shown in FigagV andVIII. A tube |02 is connected at one end to the end of the passage `|0| in the valve body vBand at the other end to a bracket |03 which supports pilot light burner P. The bracket` |03 issecured to the combustible mixture tube 80 near the blowpipe head He by meansof clamping boltsl04. f f

The bracket |03 isprovided with abore |09 which is connected to the pilot'light fuel gas tube |02. the bore |05 in the bracket is threaded and the burner P Ais screwed to the bracket at this point.'

The inlet coupling |01 'ofthe burner is provided with` a double screen |08 to clean the fuel gas and prevent the burner nozzle` |09 from being clogged. The screen |09is retained in the boref of thev burner` by means of an externally threaded locking .ring ||0.. The fuel SSLS passes from the screen*` chamber througha metering orifice ||2 which determines the'quantity of fuel'gas to-be consumed by the pilot burner. The outlet from themetering orifice I2 is internally thread- `valve 12 is then fullyopened 4and the4v heating oxygenvalve`44 isslightly opened; Fuel gas will then flow, directly-5to.` the `pilotwlight burner` P and is lightedat the nozzle |09. The pressure of thev fuel-gasin the hose lineV and the sizeof The neck `ms 4around the ermee or the orificesin the pilotlight burner P are so proi portionedin respectfto.. eachother thatv`a flame of sufficient length is produced attheend of the pilot light nozzle P to ignite the combustible mixture which is later caused to issue'from the blowpipe nozzle 38. y

The gas Saver lever 96 is then drawn `toward the handle H with the fingers of o the hand which grips the handle. The fuel gasissues through thefuelgas valve 16 of theigasfsaver Sl and the heating oxygen issues through the oxygen valve 48 of the gas saver S.` The oxygen and the fuel gasmix at the mixer 65. The. mixture nowsto the blowpipe nozzle 38` and isignited by the pilot flame ofthe pilot light burner P. `'I'he w of the heating oxygen is then adjusted by operating the heating oxygen.,` valve knob 44. "The oxygen valve of the gas saver Slbeingope'm` the oxygen ows' through this valve to the air-oxygen inlector mixer 5| and draws in thedesired nuantity of air through the air inlet. The mixture of air and oxygen Aiiows through a conduit 90', 02

to-the air-oxygenffuel .gas mixer 950, where it l mixes with the fuel gas to obtain a flame having` characteristics which the combination of parts andlconstruction of theblowpipe are designed .to produce when using a selected type of fuel gas. Since thefuel gas Vmeteringljilug 11 fl'xeswthe flow of the fuel gas for a given pressure in the fuel gas hose line,r the flame of the proper characteristics is obtained by adjusting the heating oxygen valve 44 only'. f l t When the torchis usedfor cutting metal. or `thelike, the cutting oxygen is turned on by press;-

ing the buttonV 28which mayjbe done with the thumb of the hand which attthe same time grips the` gas -`saver lever 96` andthe handle H.

The type of flame fork `which the blowpipe is 1:5y v 1 the air and engen may be mixed in different promgen valve only as the quantity of fuel gas permitted Ato iiow into the mixture is fixed by the oriilce in\the metering plug 11. Due to this n arrangement, when Athe flame attains Athe proper length and stability the combustible mixture will then contain the proportions of air. oxygen and` fuel gas the blowpipe may be designed `to produce.

,Theseproportions,l however, may be varied to produce a flame having characteristics suitable for different operations. The change in the mixture may be effected by throttling the air drawn into the air-oxygen mixture or otherwise changingthe1 construction of the air-oxygen mixer, as by substituting one mixer for another,"so that portions. '.lhe orifice in the metering'rplug 11 in'the fuel gas passage lmay also be changed to eifect fa change in the proportion of fuel gas in the'combustible mixture.

In welding certain kinase: menait is desirable to vuse low flame temperatures' to prevent the metal from being burned. rTo accomplish this Apurpose the ratio of airV to theremainder of the mixture is increased. The lowering ,of the flame temperature by the addition of air is especially useful as it makes possible the'employment of a fuel'gas having a high heat of combustion to produce either high or low temperature flames and thereby'obviates the necessity of having two kinds of fuel galsl available. l Y The addition of air to the combustible mixture within the blowpipe as compared to the absorptionof oxygen from the air without the blowpipe elects'an economy in the' consumption of the fuel gas. Inview of this featureitis also advantageous lto add air to Vthe combustible'mixture anduse a relatively high ratio of oxygen to the fuel gas in order to maintain the lname temperature the'same as. or 'even higher than, that of a normal neutral flame having no air added to the mixture within the blowpipe.

Air in a combustible mixture containing a given ratio of oxygen to fuel gas decreases the rate of name propagation when rthe mixture is ignited,

l and thereby renders lthe flame more stable and less subject tobackfires. c The air in the'combustible mixture "is especially advantageous as the oxygenk content of the mixture becomes greater than that of a mixture yielding a neutral llame since anincrease ofthe oxygen content normally increases flame propagation and decreases kthe stability of the flame.

The increase'in the ratio of oxygen to the fuel gas inv a mixture for the purpose of increasing the llame temperature and the addition of air to a mixture withiny the blowpipe -for the purpose of economizing on fuel gas and stabilizing the flame is especially advantageous in deseaming or llame machining operations, in which 'operations the dame is used in combination with a low velocity f engen cutting stream to remove -surface metal.

rref'erably acetylene isl used as the fuel gas in the g mixture. The oxygencontent of a mixture con- 2,095,747 designed n obtained'by 'remnaang the heating The 'air-oxygen-fuel gas flames also may be used for preheatlng metals for cutting with high velocity oxygen. The temperature of the ame may be made suitable for the particular class of metal or cut by controlling the proportions of the air, oxygen and fuel gas mixed within the blowpipe.

I claim:

l. A blowpipe comprising inlet conduits for air, oxygen and a fuel gas; an injector connected to said air and oxygen inlets for aspirating air into the oxygen; and an air-omgen-fuel gas mixer independently connected to the outlet from vsaid injector andto said fuel gas inlet for mixing the mixture ofair and oxygen with a fuel gas.

2. A blowpipe comprising an injector for mixing air with oxygen; said injector having a mixing chamber in 'open' communication with the atmosphere; an injector nozzle adapted to be connected to oxygen under pressure and to aspirate air into said mixing chamber; a rnixel` for 'mixing the mixture of air and oxygen with a fuel gas; said' mixer having a mixing chamber and a nozzle extending to said chamber; said second mixing chamber and associated nozzle being connected one to a fuel gas supply and the other mixer connected with the outlet from the said injector; and independent means connecting the said mixer with the said fuel lgas inlet conduit.

4. A blowpipe comprising an inlet conduit for air under atmospheric pressure; a shield for protecting said air inlet; inlet conduits for oxygen and a fuel gas under pressure higher than atmospheric pressure; an injector connected to said air and oxygen conduits and being adapted to aspiv rate air into the outlet of said injector from said air-conduit; and an air-oxygen-fuel gas mixer independently connected to the outlet of said injector and' to said fuel gas conduit.

5. A blowpipe comprising an inlet conduit for air under atmospheric pressure;- inlet conduits for oxygen and a fuel gas under pressure higher than atmospheric pressure; an injector connected to said` air and oxygen conduits and being adapted to aspirate air into the outlet of said injector from said air conduit; an air-oxygenfuel gas mixer connected to said fuel gas conduit; and aconduit connecting the outlet of said injector to said mixer, said latterconduit being of suflicient length to prevent `flashbacks at said mixer and back-fires through said air inlet.

6. A blowpipe comprising inlet conduits for air, oxygen and a fuel gas; a mixer for mixing air and oxygen connected to said air and oxygen conduits; a second mixer for mixing said mixture of air and oxygen with a fuel gas; said second mixer being connected to the outlet from said first mixer and to said inlet conduit for fuel gas; and a fuel gas metering orifice in said fuel gas conduit adapted to determine the ratio of acetylene to the oxygen and air mixture for a given pressure in the fuel gas conduit.

7. A blowpipe comprising an injector having aninlet for oxygen andan inlet for air; saidy injector being adapted to aspirate air into the oxygen'stream by means of the oxygen velocity;

`said handle for mixing oxygen and air, said in an air-oxygen-fuel gas mixer connected to the outlet of said injector and to a fuel gas conduit; a metering orifice in said fuel gas conduit; a normally closed valve in said oxygen inlet; a normally closed valve in said `fuel gas conduit and a common means for operating said valves.

` 8. A blowpipe comprising an injector.having an inlet for oxygen and an inlet for air; said injector being adapted to aspirate air into the oxygen stream by means of the oxygenvelocity; an air-oxygen-fuel gas mixer connected to the outlet of said injector and to a fuel gas conduit; a-

metering orifice in saidfuel gas conduit; a normally closed valve in saidoxygen inlet; a normally closed valve in said fuel gas conduit and a common means for operating said valves, including means for opening said `oxygen valve prior to the opening of said fuel gas valve, and closing said fuel gasvalve prior to the closing of said oxygen valve.

9. A` blowpipe comprising a handle; an air-oxygen mixer located on said handle; said-mixer let for the mixture of air and oxygen in said A air-oxygen-fuel gas mixer.

10. A blowpipe comprising a handle; a valve body attached directly to sala handle; sala valve body having' inlets for air, oxygenand Va fuel gas; an injector in said body connected to said oxygen inlet andto said air inlet; said injector being adapted to aspirato air from said air inlet by means of the oxygen flow and mix said l gas into a flowing stream of the thus-formed airoxygen mixture; and regulating the quantity o!` gases in the outlet from said injector; an airoxygen-fuel gas mixer in said valve body for mixing said mixture of air and oxygen with fuel gas; said mixer being connected to said fuel gas inlet; a blowpipe head spaced from said valve body; a conduit extending from said outlet of said injector to said head and returning to said valve body to provide a gas passage between said injector and said mixer.

11. In a blowpipe, a source of fuel gas, a source of oxygen, an injector connected with said source of oxygen and with an air bore in said blowpipe for mixing air with the oxygen by means of such oxygen, a conduit for the oxygen-air mixture, and a second injector in said conduit connected with said source of fuel gas for mixing the oxygen-air mixture with `said fuel gas to form a combustible mixture.

12. In a blowpipe, a sourcevof` fuel gas, a source of oxygen, yan injector connected with said source 13. In a blowpipe, a handle, a blowpipe head` i, spaced from said handle, a fuel gas inlet and an oxygen inlet both in said handle, an injector in the other gas.

lector being in communication with atmosphere and being supplied with oxygen from said oxygen inlet, a second injector in said handle` for. mixing the oxygen-air mixture with` fuel gas, said second injector being connected with said fuel gas inlet, and a conduit connecting the discharge end of said first-named injector with the intake end of said second-named injector, said conduit extending from said handle toward said blowpipe head and back to said handle, thereby Providing a long conduit for preventing flashbacks.

14. Ablowpipe comprising inlet conduits for air, oxygen and a fuel gas; a mixer for mixing air and oxygen connected to said air and oxygen conduits; a second mixer-for mixing said mixture of airand oxygenwith a fuel gas; said second mixer being connected to the outlet from said first mixer and to said inlet conduit for fuel gas; means for keeping constant the rate of flow gen mixture with fuel gas so as to form a combustible mixture.

16. A method of forming, and controlling the composition of, a combustible gas mixture, which comprises introducing air into a flowing stream `of oxygen; regulating the quantity of air thus introduced responsively to the quantity` of oxygen flowing per unit `of time; introducing fuel fuel gas so introduced responsively to the quantity of said air-oxygen mixture flowing per unit of time.

17. A blowpipe comprisingdmeans for introducing air intoa flowing streamof oxygen, means for regulating the rate Aof oxygen flow and the air supply responsive thereto, and means for introducing fuel gas intothethus-formed air-oxygen stream whereby the fuel gas supply is regulated responsive to the rate of air-oxygen flow.

18. Ina blowpipe, the combination of a fuel gas conduit; a combustion-supporting gas conduit including an injector device for delivering such combustion-supporting gas to be mixed with the fuel gas: means for admitting air luto one of said conduits; :and a second injector device in the conduit to which air is admitted adjacent v the `point of ladmission of such air. 19. In a blowpipe, the combination of a body having two chambers severally communicating with a fuel gas inlet passage and an oxygen inlet passage; an injector device removablysecured.

in one of said chambers; means for admitting air into the chamber containing said removable injector device; and means, including an injector device in the other ofsaid chambers. for delivering the air-gas mixture to be mixed with wrmo'r J. Jaconsson.