US2376413A - Blowpipe nozzle - Google Patents

Description

May 22, 1945.

R. S. BABCOCK BLOWPIPE NOZZLE Filed Feb. 26, 1941 INVENTOR ROGER s. BABCOCK BY ATTORNEY Patented May 22, 1945 BwwmrnNozun Roger s. Babcock, Plainfield, N. 1., assignor Union Carbide and Carbon Corporation, a corporation of New York Application February 26, :1941, Serial No. 380,848 1 This invention relatesto ablowpipe nozzle and more particularly to airy-acetylene cutting blows pipe nozzles for cutting metallic bodies in which a stream of oxidizing gas, such as oxygen, is applied to a portionof the metallic body preheated by a flame produced by the combustion of a mixture of oxygen and acetylene.

Oxy-acetylene cutting is a process of severing ferrous metals by utilizing the rapid chemical reaction which takes place between heated iron and oxygen. The heat liberated by this reaction is suflicient not only to melt the iron oxide but also to melt some of the steel or iron. (In a practical application of the oxy-acetylene cutting process, the Jet or stream of oxygen which does the "cut ting issues from an orifice in the center of a nozzle or tip of a cutting blowpipe. Surrounding the cutting orifice oi the nozzle or tip are several smaller orifices for oxy-acetylene heating flames. These are used to preheat the metal to its kindling temperature. Theoretically, the heat of the cutting reaction should be sufficient to keep the cut going after it has started. In practice, however, the heating flames arekept burning constantly to melt the surface scale and thereby insure the proper reaction with continuous and rapid cutting. The flow of cutting oxygen is controlled by a conveniently located valve on the blowpipe handle, and the cutting oxygen jet may be guided along any line desired, whether straight, curved, or irregular, and may also be inclined at an angle, as in deseaming.

To start cutting, the blowplpe is held with the nozzle perpendicular to the surface of the work and with the inner cone of the heating flame about inch above the end of the line to be cut on the edge of the work. The blowpipe is held steady until this spot has been raised to'a bright red heat, and the cutting valve lever is then pressed down slowly while moving the blowpipe along the line to be cut. If the out has started promptly, a shower of sparks will fall from the underside of the work, thus indicating that the cut is penetrating clear through. The movement of the blowpipe is then regulated Just fast enough so that the cut continues to penetrate the work completely.

As used throughout this specification and in the claims, the term oxy-acetylene cutting is intended to include all o'xy-acetyleneworking of ferrous metals, such as scarfing, deseaming, desurfacing, grooving, slotting, severing, and the like.

The principal obiect of this invention is to pro.

1 Claim. (Cl. 158-274) erating characteristics superior to those now known. Other objects of this invention are to improve both cutting and deseaming nozzles in general by providing means associated therewith for 5 increasing the overall efliciency of the thermochemical reaction; to produce smoother and more uniform reaction zones by controlling the radial expansion of the cutting gas; to obtain a ring preheat flame, theuniformity of which, being essentially independent of the number of orifices producing said ring flame, increases the cutting e1- ficiency; to provide an oxy-acetylene nozzle having a skirt extending beyond the normal face of the nozzle, the size of said skirt being proportioned to obtain the, best operating characteristics of the nozzle; to provide an improved means for utilizing discharged preheat gases to retard the radial expansion of the oxygen jet discharged by an oxygen orifice to thereby ingo crease the axial velocity of. the oxygen jet to a value above the acoustic.

According to the invention there is provided a blowpipe nozzle consisting of a conventional cutting or deseaming nozzle having a cylindrical 25 flange or skirt extending beyond the normal face thereof. The skirted portion is constructed in a manner whereby a sufiicient quantity of the heat induced therein will be conducted backto the. nozzle body, preventing deterioration 01' such skirt and increasing the heat content of the preheat gas, which increase in heat content of the gas improves the overall efiiciency of the nozzle. In addition to the construction and arrangement of the skirt to properly utilize the induced heat, it also has internal dimensions, which, in conjunction with the arrangement and size of the preheat and cutting oxygen orifices, produce a ring preheat flame and an oxygen stream having divergent Jet characteristics.

More particularly, according to the invention, the skirt extends beyond the normal face of the nozzle so that the skirt opening, coupled with the exhausting preheat gases, retards the radial expansion of the oxygen jets beyond the oxygen orifice and thereby increases the axial velocity of the oxygen Jet to values above the acoustic. For best results, it has been determined by actual tests, that the skirt should have a length equal to or greater than the lengthof. the inner cone of the preheating flame. Further, that the internal diameter of the skirt adja'centto the normal face of the nozzle should be equal to or greater than the sum of the diameter of the proheat hole circle plus the diameter of one preheat hole. preferablv mural a. ma cum y. 4k. Munof said circle plus the width of three of said precuttings-swell. The nozzle i3 is surfaces,

heat holes. in addition the preheat hole circle should have a diameter substantially equal to one and one-half that of the cutting oxygen orifice. The skirt itself may be either cylindrical, convergent, or divergent, the diameter of the skirt being measured at the rearmost portion thereof. Referring to the accompany! drawing:

' 'Fig. 1 is a view in side elevation of a cuttingblowpipe having a nozzle embodying features of thisinvention: Fig. 2 is an enlarged fragmentary cross-sectional view of the head portion of the blowpipe showninl lg. 1; v

Fig. 3 is an enlarged fragmentary sectional similartol 'igz'ofthenozzle tip;

'l igJisaplanviewoftheendofthenozzie view 1 shown in m. 3:

Fig.5 is a fragmentary sectional viewshowing the nozzle in operation: and

' F 88; 6 and 1.81% longitudinal and Wet sections, showing the use of the nozzle in cutting a body steel, 7 being taken-on line |-,-I of Fig. 6;

the cutting blowpipe ll, shown by way'of example, an oxy-acetylene flame ii is produced at a series of preheat gas openings I! in the blowpipe tip'or nozzle it, which surround a larger- "the blowpipe through a hose ll while acetylene issupplied to the blowpipe through a hose Thus cutting oxygen is delivered to central passageway SI of the nozzl l3 through pipe 32, while a combustible mixture of oxygen and acetylene is delivered through pipe 33 to the preheating Gas 4 orifices I! which surround the cutting oxygen oriflce 84 in the normal end face 34 of the nozzle.

According to the invention, both one and twopiece nozzles are equally efficient and the addition of a skirt to otherwise conventional oxy-acetylene nozzles having either a conical divergent cutting oxygen orifice or a cylindrical cutting oxygen orifice, was found to have a definite beneflcial effect upon the operation of the nozzle.

The skirted nozzle, shown in the drawing by way of example, consists essentially of an outer body or casing 35 and an inner member 38 con-. taining the central oxygen passage ll terminating in orifice l4, and the preheat gas ports it. The

snember 86 is shown connected to partfl by a nipple 38 but may be integral with the latter. The

outer casing 35 has a cylindrical flange 39 on the rear portion thereof adapted to be engagedby the externally threaded nut 16 which surrounds the casing 35 and secures the nozzle II to the blowpipe head 25. The body thickness of this outer member 35 must be great enough to conduct a sufficient quantity of 'heat from skirt 48 to prevent damage to the skirt 40 by reason of its close proximity to the high temperature flame Such hoses areconnected to the blowpin M by tions 2| and 22, respectively, the supply of oxygen, and acetylene being adjusted by valves and 24.- Oxy en and acetylene are mixed within-the blowpipe to provide a suitable combustible mix-v j ture for supplying the preheating flame, while the cutting oxygen is conducted directly fromthe nozzle I: by .way of the cut l il oxygen, valve.

Conventional oxyeacetyiene cutting blowpipes are of either the low-pressure, or medium-pres .sure type. -Simply by changing the size of the cutting-,nozzle or cutting tip, a single cutting biowpipe may be adapted to cut a wide range of;

- the preheat gas to flow through the reheat or- Y names used on cutting blowpipes may be of either metal thickness. Furthermore, interchangeable one-piece or two-piece construction. In the onell emanating from the preheat ports I2. The

inner member-3B, nipple 38 and part 31, generally cylindrical in shape, are slightly smaller than the inner diameter of easing It in order to .provide an annular passageway 42 for the oily-I A On the rear portion of acetylene gas mixture.

part 31 of the inner member 38 is a cylindrical flange 43, the forward surface of which coacts with the cylindrical flange 39 on the casing SI f. toformagas-tightseal. 1 I Y The inclined seats 21 and 28 coacting with the corresponding seats 29 and 30 in theblowpipe '1 7 head .25, form gas-tight seals and prevent the mixture of the preheat gas with the cuttingoxygen as these gasses pass from the blowpipe head "45 2! to nozzle passages 3| and 44, respectively. On oxygen inlet ii to, the'central orifice 14 of the the forward portion of the inner member 38 is a ;conical flange 45 in which the series of preheat gas ports [2 are annularly disposed and concen- .trically aligned with the central oxygen orifice 5 I4.- This conical flang 45 conforms in shape .lwithfithe forward conical portion of the casing 35,

face it and longitudinal axes C of the preheat orifices l2 form included angles of about 9 and heating flames and cutting jets are drilled through I a solid piece of metal, usually pure copper.., The

cutting, cast-iron cuttinmsheet-metal cutting, I

* 'desin'facing, and d. While a'hand-cut-j ting blowpipe has been shown inthe drawing, it

will be understood that the invention isnot lixnited thereto, but includes or of the one-piece swaged type. Such types are biowpipes for machine secures a artments m of the blowpipe II by means of a hollow not I.

which is threaded into the head a and forces seating surfaces 21 and 28 on the nozzle into seal-q Inthe example of the nozzle 00 "5, respectively, with the longitudinal axis of the.

cutting oxygen orifice l4. 7 i

illustrated in Fig. 2, the inner piece of the two-piece nozzle consists of the member 38 and'part 31 connected by the nut 38 However, it will be understood by those skilled in: the art that the entire inner piece may consist of a single member of conventional style..-, The nozzle-may also consist of the so- "called Zobel type, or the conical divergent type,

well known to those skilled in the art.

Referring to Fig. 3, from experiments actually conducted on skirted nozzles, according to the invention, it has been found that the diameter B of the preheat hole circle should be about one and one-half times the diameter of the cutting oxy en orifice l4. and that the internal diameter F of the skirt 40, for good results, should be approximately as'rausequal to or slightly greater than the sum of the upon the normal length of the inner cone ll, Fig. 5, of the preheat flame II and should be equal to or slightly longer than the inner cone I. It has also been observed that when cutting work with the skirted nozzle It, the tendency for slag t find its way into the preheat holes I! is almost completely eliminated and therefore permits the use of a large number of small preheat flame ports I! when necessary.

In operation, the preheat flames emanating from the series of ports are adjusted so that the inner cone I does not extend beyond the inner surface of the skirted portion I. The oxygen stream 41 emanating from the central oriflce I4 partially fllls that area surrounded by the skirt 40 and allows a narrow space for the passage of the outer envelope 48 or the gases forming the preheat flame II. By so. confining the outer envelopes of the individual flames, a ring flame isessentially obtained, adding to the efllciency of the nozzle and eliminating the necessity for an excessively large number or small preheat gas ports 12. Furthermore, it has been found that, with a properly designed skirt 40, the outer an- "nular envelope 48 of the preheat flames II, which surround the oxygen stream '41, extends approximately 10 to 12 inches beyond the face of the nozzle I 3. When employing the cylindrical bore cutting oxygen oriflce il in the skirted nomle J8, the usual radial expansion of the gas 41 upon being discharged into the atmosphere is partially prevented because of the cushioning efiect provided by the presence of the annular heating flame 48, producing let characteristics very similar to those obtained from a conical divergent nozzle, as evidenced. by the kerf contour.

The stream shape shown in Fig. 5 is representative of that obtained with a skirted cylindrical nozzle l3 constructed in accordance with the invention. The length, uniformity and sym-* metry of the outer preheat envelope 48 is strikinsly obvious and the outer envelope It does not undergo any great degree of radial expansion which condition, of itself, indicates that a great part of the heat is efliciently applied to the cutting area to aid the operation.

Referring to Figs. 6 and 7, a steel body 48 is shown being cut by the oxygen stream 41 of Fig. 5 assisted by the oxy-acetylene heating flame It. The nozzle II is constructed and arranged to cause the zone of secondary combustion of said flame to flow with the cutting oxygen to form a composite cutting stream in which the cutting oxygen is surrounded by a single well-defined heating flame. The skirted cylindrical bore nozzle I3 is definitely superior, in cutting the steel body 48, than any known non-skirted nozzle because the walls 50 of keri 5| are smoother and the actual operating eiiicien-cy is higher.

Among the advantages of the skirted nozzle of the invention, over those formerly known, may bellsted: the high overall efliciency of the operation because of the added heat applied to the work, smoother and more uniform cuts because of the added heat and the production oi an essentially ringyp flame.

It has been round, through investigation, that the amount of heat applied to a metal body during a conventional cutting operation has an iniurious effect upon the resultant keri walls, in that an oxidic coating formed on these walls, in such instances, becomes loose and pieces thereof are drawn into and disrupt the cutting stream. 'ihc most probable cause of such loosening of oxide is the insufliciency of heat, that is, the oxide is formed through the combustion of the steel and within a short interval of time, with ordinary nozzles, sufllcient cooling may take place to cause theoxide to chip, because of the contraction of the base metal.

into the keri 5|, Figs. 6 and 7, and keeps the oxide closer to the temperature of the adjoining basemetal ,so that the outside cools more slowly and there is no chipping or loosening of the scale in the vicinity of the reaction zone. This condition results in the production or highly smooth and uniform walls Iii.

It is known that a skirted nozzle hasheretofore been used, primarily as a matter of necessity, especially with gases other than acetylene, such as propane, having a relatively low rate oi flame propagation compared to the oily-acetylene flame. With such iuel gases, the normal lineal velocity of gas at the mouth of the nozzle greatly exceeds the rate of flame propagation and causes the flame to be blown away-irom the face of the nozzle. To overcome this difliculty, a means must be employed to decrease the gas velocity at the periphery of the gas stream without affecting the internal velocity of, the stream as merely in order to insure stable operation of the apparatus. A skirted nozzle for fuel gases other than oxy-acetylene was, therefore, adapted for such purpose and has since been considered standard practice. The skirtedtype of nozzle 40 heretotore used for fuel gas other than acetylene,

,gtarding the normal free expansion of the oxygen stream outside of the. oxygen oriflce. If the such as propane, was not intended to be used for city-acetylene cutting because, due to the, intense heat of the oily-acetylene flame, the skirted portion of the nozzle was quickly burned away. Therefore, the development of the art was such that nozzles for oxy-acetylene cutting inair generally had a smooth non-skirted end face,. while cutting nozzles for fuel gasps other than normal expansion is retarded by the presence of a surrounding medium moving at a velocity somewhat less than the acoustic, but appreciably faster than the surrounding air streams, then radial expansion of the oxygen stream will be retarded and an increase in the axial expansion away from the oriflce must result. Such a theory presupposes less turbulence in the oxygen stream and a more uniform keri width. These have generally been observed in actual tests with cuttnlg nozzles embodying the invention.

The skirt material should be able to withstand the heat from the oxy-acetylene flame or to have a conductivity high enough to prevent localised heat from melting the lkiitid section. Th8! However, with a skirted oxy-acetylene nozzle made and used according to the invention, additional heat is drawnconditions are satisiactorily ioundin the use oi copper which is cheap, readily machined,- and already used in nozzle construction. The skirt should be an extension of the nozzle, in the oneiece construction, oran extension oi the externai member if made of two-piece construction. Buiiicient material should be'allowed in the section adjoining the skirt of the nozzle body to provide for the required heat transfer.

Among the more important features of the present invention are the following:

1. Theuse of a skirt section extending beyond the normal face of an oxy-acetylene nozzle.

This is only possible for high flame-temperature gases, through the spacing of the preheat holes between the oxygen orifice and the surrounding skirt, so that the preheat flame cones do not contact the skirt. Absorption of heat by the skirt is therefore reduced because the flames do, not contact the skirt material. The heat picked up through convection and radiation is of a relatively small amount.

2. The use of a skirt section involving preheat and skirt dimensions within certain proportional limits for optimum operation with oily-acetylene.

By holding the dimensions within certain limits,

satisiactory operation or the nozzles can be re- 'strlcted to the use of oxy-acetylene alone. The time intensity of other commercial fuel gases is so low by comparison with the more rapidly burning on-acetylene flames that their use with the optimum, skirted, oxy-acetylene design nozzle is precluded.

3. The use of a skirted section extending be- I yond the normal face of the nozzle so that the skirt opening, coupled with the exhausting preheat gases, retards the radial expansion of the oxygen jet beyond the oxygen orifice and thereby by increases the axial velocity of the oxygen Jet to values above the acoustic.

Keri samples of cuts made with skirted, cylinout this point.

asraue drical bore;;oxy-acetylene nozzles seem to bear will out faster and more eiliciently than known o'xy-iuel gas nozzles which are not suited to the high temperature of the oxy-acetylene flame. In

such skirted oxy-acetylene cutting nozzles, the

diameter oi. the preheat hole circle should be held within a definite relationshipto the diameter of the cutting oxygen orifice, and the diameter of the mouth or the skirt should be maintained within certain limits with respect to the preheat hole circle.

What is claimed is:

A blowpipe nozzle having an end face, a central cutting oxygen orifice terminating at said end face and adapted to discharge a cutting stream of oxygen, a plurality of oxy-acetylene preheating gas ports terminating at said end face in a circle concentric with said orifice. and adapted to discharge Jets 0! oxy-acetylene preheating gas which, when ignited, produce flames each having an inner cone and an outer heating envelope, andmeans for merging and concentrating said outer envelope symmetrically about said cutting stream for a substantial distance axially thereof into a single annular heating flame, said means comprising an annular skirt on said nozzle adaptedto surround said fiames in concentric relation with said oxygen stream, said skirt having an inner diameter adjacent to said lace equal to the sum of the diameter of said circle and the width of three oi said ports, said circle havinga diameter equal to substantially one and one-halt times the diameter of said orifice. I ROGER S. BABCOCK.

' Radial drilllngs through ,sklrted section emitted preheat names under noimalconditions which indicatedfthat a slight 'back pressure exists within the skirt 'cavity. 1 1 In conclusion, skirted oily-acetylene nozzles constructed according to the invention

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