US 2767782 A
Description (OCR text may contain errors)
United States Patent BLOWPIPE CARTRIDGE-TYPE MEDIUM- PRESSURE GAS-MIXER Clifiord C. Anthes, Union, N. J., assignor to Union Carlazide and Carbon Corporation, a corporation of New ork Application January 16, 1952, Serial No. 266,646 6 Claims. (Cl. 15827.4)
This invention relates to blowpipes and more particularly to internal gas mixers of the medium-equal pressure type for combining a combustion supporting gas, such as oxygen, and a combustible gas, such as acetylene, to produce a gas mixture suitable for burning upon discharge from the blowpipe.
In factories and plants which are already equipped to supply acetylene at medium pressures, the attempted use of any additional oxy-acety'lene processes exceeding the maximum demand of the equipment, causes the gas pressure of the acetylene to fall below that required by conventional medium pressure blowpipes. Thus, it is virtually impossible to extend the use of such equipment to additional processes in spite of the fact that a considerable investment has been made in the original medium pressure gas supply.
The main object of this invention is to provide a blowpipe mixer of the medium pressure type which solves such problem without changing the original medium pressure gas supply set-up, so that the use thereof can be extended by the addition of oxy-acetylene processes which exceed the former maximum demand thereof.
Heretofore, the maximum capacity of medium pressure blowpipes has been limited by the need for large cushioning chambers located between the throttle valve and the mixing chamber of the blowpipe, which in the case of a 1,000 cubic foot per hour blowpipe, for example, requires a cushioning chamber in the form of a gas passage which is about 8 feet long, involving the use of considerable copper or brass which now is expensive and highly critical, and also makes the blowpipe cumbersome and heavy. A similar problem arises in the increased length of the mixed gas passage for larger capacity blowpipes.
A very important additional object of the invention is to provide a mixer which practically eliminates the necessity for any such large cushioning chamber, or for the relatively long mixed gas passage, regardless of how great the capacity of the blowpipe is, up to and even greater than the 1,000 cubic foot per hour size.
Further objects are to provide a mixer that is simple and economical in construction, stable in operation, and which is highly resistant to flashback even in the event of a backfire. Other objects will appear from the following description.
According to the invention there is provided a cartridge type mixer for equal-medium pressure blowpipes having a longitudinal acetylene or other fuel gas passage having a portion through which by virtue of its constant cross-sectional area the acetylene gas flows freely at a velocity of the order of l00-500 feet per second, dis charging into a gas mixing chamber. An elongated annular oxygen gas passage surrounds such acetylene gas passage in spaced relation therewith, so that oxygen supplied to the inlet end thereof, flows in the same direction as that of the acetylene gas, through a thin annular wire drawing space the width and length of which are critical, H The length of such annular oxygen passage is at least five times the diameter thereof. The oxygen gas discharges from the outlet end of such annular passage through at least two diametrically opposed oxygen gas metering ports into the throat of such gas mixing chamber, the cross-sectional area of which is increased with respect to that of such portion of the acetylene gas passage so that the velocity of the resulting oxy-acetylene gas mixture is no less than that of the acetylene gas in such portion. The oxy-acetylene gas mixture is subsequently delivered to the point of burning outside of the blowpipe through a mixed-gas passage.
A remarkable and unexpected advantage of the mixer of the present invention is that, regardless of the capacity of the blowpipe, the point of throttle, normally in the form of a blowpipe needle valve for each gas, can be located immediately upstream of the mixer. Heretofore, this has not been possible as will be explained below. Manufacturing costs are reduced approximately 10 percent by the elimination of old flashback suppression means such as flashback coils, return bends, and dead end tubes in either of the feed gas passages upstream of the mixer.
Improved flashback resistance results with the mixer of the invention, and the blowpipe can be backfired to the point where the tip-end gets red without a flashback occurring. No other mixer can take such punishment over as wide an operating range of gas pressures and degree of throttle of the gas control valves. As high as 250 p. s. i. oxygen pressure can be used and the mixer still retains good flashback resistance. Flashback resistance is also good at any acetylene pressure from the very minimum necessary to sustain a flame on the tip, such as one pound per square inch, or lower, up to the maximum permissible acetylene pressure 15 p. s. i. Heretofore, with previous mixers a minimum acetylene pressure of 5 p. s. i. has been required.
The advantage of having the point of throttle immediately upstream of the point of mixing is of great importance in welding and cutting blowpipes. This importance increases in magnitude in the case of large-flow blowpipes having a consumption of as much as 1,000 cubic feet per hour of each gas. Heretofore, such large flow blowpipes required lengths of gas passages up to 8 feet between the point of throttle and the point of mixing. Such distance is obviously very expensive and impractical.
The mixer of the invention permits operation of the blowpipe at equal and relatively low fuel gas and oxygen pressures. Regardless of the size of the welding or heating head used with this mixer, the full rated capacity of the device, unexpectedly as it may seem to those skilled in the art, is obtained at a blowpipe inlet pressure of each gas of the order of 5 p. s. i.
The novel mixer construction of the invention also eliminates critical factory gauging dimensions heretofore required to maintain maximum flashback resistance in conventional mixers, for example, so-called end-clearances and axial taper clearances. Critical gas-metering clearances are maintained on diameters that are more'easily held in manufacture than are axial dimensions. Furthermore, assembly technique is not critical as'in the case where axial clearances must be relied on.
In the drawing:
Fig. 1 is a longitudinal sectional view of a cartridge mixer illustrating the invention;
Fig. 2 is a cross-sectional view taken on line 2-2 of Fig. 3; Fig. 3 is an enlarged view similar to Fig. l of the cartridge;
Fig. 4 is a longitudinal sectional view of a modification which is especially suitable for very large capacity blowpipes; and
Fig. 5 is a cross-sectional view taken on line 5-5 of Fig. 4.
Referring to Figs. 1, 2 and 3 of the drawing, the illustrated mixer M comprises a cartridge-shaped, elongated, tubular member 10, composed of metal, preferably bronze (but copper or brass can be used), having an axially extending, elongated .passage 8 for acetylene, or other fuel gas, consisting of an inlet chamber 12, a gas metering port 14, an intermediate portion 16, and a gas mixing chamber 18. There is thus provided a free acetylene gas passage which extends centrally through the mixer, having no restriction except that of the actual acetylene gas flow metering port 14, the cross-sectional area of which port depends upon the gas handling capacity of the blowpipe.
The diameters of the acetylene passage 8 are critical in three locations; i. e., in the metering port 14, in the intermediate portion 16, and in the mixing chamber 13. The diameter of the metering port is governed by the size of the blowpipe; for example, for a blowpipe having a capacity of 25 cubic feet per hour of acetylene gas, such diameter is 0.047 inch. The length of the metering port is preferably about 10 to times the diameter thereof.
The cross-sectional area of the intermediate portion 16 of the passage 8 is preferably such that the calculated velocity of the acetylene gas flowing freely therethrough falls between 100 and 500 feet per second, 350 feet per second being preferred. While the length of such portion 16 is not critical, and may be much shorter than that illustrated, it is important that the wall of the passage he smooth and of constant diameter from end-to-end to eliminate pockets in which burning can take place. By maintaining the preferred gas velocity in the intermediate passage 16, excessive pressure drop in the acetylene stream is avoided, which aids in suppressing a flashback by permitting a delay of return of acetylene until the fire is quenched.
The cartridge or tubular member 10 fits in a suitable socket 20 in the blowpipe body 22, or inside another tubular member, such parts being formed to provide a .relatively thin, annular, elongated, wire-drawing, oxygen passage -24 which surrounds the longitudinal axis of the acetylene gas passage in spaced concentric relation with the latter. The tubular member 10 is also provided with at least two diametrically opposed oxygen flow metering ports 26 for delivering the oxygen gas from the outlet end of the annular passage 24 directly to the throat of the mixing chamber 18. This construction is novel and important.
The annulus of the oxygen passage 24 is critical in thickness and length. The thickness of such annulus is gauged to maintain a fair velocity of oxygen flow through the passage in order to suppress flashbacks; and the length of the passage 24 is at least five times the diameter of the annulus. Said diameter should be such that an annulus of .005 to .015" thick will pass the full rated capacity of oxygen at the preferred velocity which is normally somewhat lower than the velocity of the acetylene in the acetylene passage 16. The size of the radial oxygen metering ports is determined by the capacity of the mixer and is equal to the capacity of the acetylene metering port 14. In each blowpipe the number of oxygen metering ports 26 should not be less than two, and up to six they should be arranged in diametrically opposed pairs, although any number of metering ports can be used.
The cross-sectional area of the gas mixing chamber 18 is critical, being additionally greater than that of the passage portion 16 so that the velocity of the oxygen and acetylene mixture, in flowing out of the mixer, is equal to that of the acetylene gas in such intermediate portion 16. From the mixing chamber 18 the gas is delivered through "a suitable mixed-gas passage 28 to the point of burning outside'of the blowpipe. The cross-sectional area of such mixed-gas passage is always at least as great as that of the gas-mixing chamber, but may be greater for relatively large capacity blowpipes.
In operation oxygen gas is supplied to the mixer M from an oxygen cylinder 30 through an adjustable gas pressure regulator 32 and a throttle valve 34 which are connected in a suitable oxygen supply line to an inlet passage 36 leading tothe gas inlet end of the annular oxygen passage 24 of the mixer. Similarly, acetylene gas is supplied to the inlet chamber 12 from an acetylene cylinder or generator 49 through an adjustable gas regulator 42 and a throttle valve 44 in a suitable acetylene gas supply line including inlet passage 45.
In operation the oxygen valve 34 is opened and the regulator 32 is adjusted to indicate a pressure of five pounds per square inch. The oxygen valve 34 is then closed and the acetylene valve 44 is opened and the acetylene regulator 42 is also adjusted to show a pressure of five pounds per square inch. The acetylene valve 44 is then closed, and both throttle valves 34 and 44 are opened when it is desired to use the equipment. The gases flow through the mixer M, are effectively mixed therein, and the resulting gas-mixture, discharged from the blowpipe by way of a suitable mixed-gas passage, is ignited.
A variation of the cartridge-type mixer which is especially suitable for very large capacity blowpipes, but also is suitable for any capacity, is shown in Figs. 4 and 5.
Such mixer includes an elongated tubular member 46 having an elongated passage 48 for combustible gas, such as acetylene, and an enlarged recess 50 in which .is fitted an insert 52, such insert being provided with a plurality of metering gas ports 54 having one end in communication with a gas distribution chamber 56 formed at the inner end of such recess. The insert is also provided with a plurality of preliminary gas mixing chambers 58 each of which is axially alined and in communication with a corresponding one of the gas metering ports 54. Such preliminary gas mixing chambers discharge into a major mixing chamber 60 which is in axial alinement with the elongated combustible gas passage of 48 in the member 46.
The member 46 fits in a suitably shaped socket of an outer member 62, the parts being formed to provide an axially elongated, annular, combustion supporting gas passage 64 which surrounds the elongated, combustible gas passage 48 in spaced concentric relation therewith. An inlet passage 66 for combustion supporting gas is provided in the member 62 for delivering such gas to one end of such annular passage 64, the member 46 being provided with a plurality of combustion supporting gas metering ports 68, each of which is in communication with a corresponding one of the preliminary gas mixing chambers 58, by way of enlarged openings 70 formed in the wall of the insert 52.
Said modified arrangement has the advantage, in the case of large capacity blowpipes, of utilizing a number of individual, preliminary gas-mixing chambers, the transverse area of which is held down to a value wherein effective cooling is attained through intimate contact of the gas with the wall of the passage. Thus, flashback following a backfire is minimized even in the case of large capacity blowpipes.
Good flashback resistance is a function of the pressure build-up resulting from a backfire which forces the gases leading up to the point of mixing back into the respective gas passages. Therefore, the recovery time before the raw gases come together at the point of mixing is great enough so that any combustion within the mixedgas tube is extinguished. This particular invention accomplishes the desired result by the long, narrow, cylindrical, annular passage formed by the inside diameter of the mixer tube and the outside diameter of the mixer itself. The actual width of such annulus is preferably inzthe neighborhood of only five to fifteen thousands of an inch. This narrow annulus, aside from atfordingthe required delay in return of pure oxygen, also has a beneficial quenching eifect on the flame front as the latter is forced back into the oxygen passage by the pressure of a backfire, inasmuch as the length of the annulus axially of the passage is at least five times the diameter thereof.
The acetylene passage in portion 16, Figs. 1-3, upstream of the point of mixing has a restriction for the same purpose in the form of the metering port 14. The combination of quenching, cooling, and retarded flow recovery of both gases to the point of mixing, as afforded by this invention gives it superior flashback resistance compared to prior mixers.
The length of oxygen annulus upstream from the point of mixing is dependent on such factors as throttle valve location, rated gas capacity, and type of fuel gas. In case of the blowpipe shown for mixing oxygen and acetylene, where the valves 34 and 44 are located immediately upstream of the point of mixing, the length of such annulus should be a minimum of 1 /2 inches. Prior blowpipes with conventional mixers required as a very minimum five or six inches of gas passage between the point of throttle and the point of mixing.
, The mixer of this invention can be used to advantage in all types of blowpipes: welding, cutting, deseaming, and heating, for example. The invention has particular advantage in cutting blowpipes in which it is common practice to throttle the preheat oxygen from a relatively high oxygen pressure. The fact that the flashback resistance is maintained with the invention, even when throttling from oxygen pressure as high as 250 p. s. i., fully covers the entire operating range of any blowpipe.
An unexpected advantage of the mixer of the present invention is that the length of the mixed-gas passage can be very greatly increasedwhich was not possible in the past inasmuch as the mixer had to be tailored to the length of the blowpipe.
It will be understood by those skilled in the art that the principles of my invention may be adapted for fuel gases other than acetylene by suitably rcproportioning the sizes of the various gas passages and chambers with out departing from such invention, as defined by the claims.
1. A medium pressure oxy-acetylene blowpipe mixer comprising means provided with an elongated acetylene gas passage having at least one relatively long acetylene metering port, and a gas mixing chamber in communication therewith; means providing a relatively thin elongated annular oxygen gas passage; means having at least two oxygen metering ports for conducting oxygen from the outlet end of such annular passage to such mixing chamber, the total gas metering capacity of such oxygen metering ports being substantially equal to that of such acetylene metering port at equal delivery pressures of the oxygen and acetylene, the length of said annular oxygen passage being at least five times the annulus diameter thereof; the cross-sectional area of a portion of the acetylene passage being such that the acetylene gas flows freely therethrough at a relatively constant velocity, and the cross-sectional area of said gas mixing chamber being such that the combined oxygen and acetylene gas flows axially therethrough at a velocity substantially equal to that of the acetylene through such portion.
2. A medium pressure oxy-acetylene blowpipe mixer comprising an inner member provided with an elongated acetylene gas passage having a relatively long acetylene metering port, an enlarged intermediate portion, and an enlarged gas mixing chamber provided with a throat in communication with such portion; all in axial alinement; an outer member surrounding said inner member and forming therewith a relatively thin elongated annular oxygen gas passage in spaced concentric relation with such acetylene passage, said inner member having at least two radial oxygen metering ports for conducting oxygen from the outlet end of such annular passage to the throat of such mixing chamber, the total gas metering equal to that of such acetylene metering port at equal delivery pressures of the oxygen and acetylene, the length of said annular oxygen passage being at least fivev times the annulus diameter thereof; the cross-sectional areaof such intermediate portion of the acetylene passage being such that the acetylene flows therethrough at a relatively constant velocity, and the cross-sectional area of said mixing chamber being such that the combined oxygen and acetylene gas flows therethrough at a velocity substantially equal to that of the acetylene through such intermediate portion.
3. An equal-medium pressure blowpipe gas mixer comprising means providing an elongated passage for combustible gas having in axial alinement a combustible gas inlet chamber, a constricted combustible gas metering port, an enlarged intermediate portion, and an enlarged gas mixing chamber provided with a throat in communication with such portion; means providing an axially elongated annular passage for combustion supporting gas surrounding such combustible gas passage in spaced concentric relation and having an inlet for such gas at one end thereof and at the other end a gas outlet consisting of at least two combustion supporting gas metering ports leading to the throat of such gas mixing chamber, the total capacity of such combustion supporting gas metering ports being substantially equal to that of such combustible gas metering port when such gases are delivered at five pounds per square inch pressure to the respective gas inlets of the mixer, the cross-sectional area of such intermediate portion of the combustible gas passage being such that the combustible gas will flow freely therethrough at a constant velocity of between 100 and 500 feet per second, the cross-sectional area of the gas mixing chamber being such that the resulting gas mixture flows axially therethrough at a velocity substantially equal to the velocity of the combustible gas in such intermediate portion, the width of the annulus constituting the combustion supporting gas passage being between 0.005 and 0.015 of an inch, and the length of such annular passage being at least five times the diameter thereof, separate means including throttle valves for delivering combustible and combustion supporting gases to the respective gas inlets of the mixer, and means providing a mixed-gas outlet passage for conducting the gas mixture from such gas mixing chamber to a point of combustion outside of the blowpipe.
4. An equal-medium pressure blowpipe gas mixer comprising means providing an elongated combustible gas passage discharging into a distribution chamber, means providing a plurality of combustible gas metering ports having the inlet ends thereof in communication with such distribution chamber, means providing a plurality ofpreliminary gas mixing chambers each of which is axially alined and in communication with a corresponding one of such gas metering ports, means providing a major mixing chamber in axial alinement with such elongated combustible gas passage and in communication with the outlet ends of such preliminary gas mixing chambers, and means providing an axially elongated annular combustion supporting gas passage surrounding such elongated combustible gas passage in spaced concentric relation and having an inlet for combustion supporting gas at one end thereof and at the other end an outlet consisting of a plurality of combustion supporting gas metering ports, each of which is in communication with a corresponding one of such preliminary gas mixing chambers, characterized in that the cross-sectional area of the major mixing chamber is greater than that of the total cross-sectional areas of the preliminary gas mixing chambers, and the cross-sectional area of each of the latter is greater than that of the corresponding gas metering port, whereby the gas flows at substantially equal velocities through the port and corresponding preliminary gas mixing chamber, and the passages are of successively decreasing cross-seccapacity of such oxygen metering ports being substantially tional area in the direction of a backfire so that the shock 7 thereof can be absorbed and a subsequent flashback extinguished thereby.
5. An oxy-fuel gas blowpipe mixer including mixed gas passage means having a common mixed gas discharge passage, fuel gas passage means communicating with said mixed gas passage means, and oxygen passage means having an elongated annular oxygen passage coaxial with at least a portion of said fuel gas passage means, said oxygen passage means also having radially arranged oxygen metering port means in communication with the outlet end of said annular oxygen passage, said fuel gas passage means having a group of fuel gas metering port means in parallel arrangement with one another, said mixed gas passage means also having a plurality of gas mixing chambers each communicating with 2. corresponding one of such fuel gas metering port means with a corresponding one of such oxygen metering port means, the total gas metering capacity of such fuel gas metering port means being substantially equal to the total metering capacity of such oxygen metering port means at equal fuel .gas and oxygen supply pressures, such gas mixing chambers all being in communication with such common mixed gas discharge passage, the cross-sectional area of each of such gas mixing chambers being greater than that of the adjacent portion of the fuel gas metering port means and the total cross-sectional area of such gas mixing chambers being smaller than that of such common mixed gas discharge passage.
6. A' blowpipe mixer as claimed in claim 5, characterized in that the length of the annular oxygen passage is at least five times the inner diameter thereof and that the thickness of the annulus constituting such passage is between 0.005 and 0.015 inch.
References Cited in the file of this patent UNITED STATES PATENTS 782,632 Waldbaur Feb. 14, 1905 1,419,168 Oman June 13, 1922 1,882,420 Hammon .Oct. 11, 1932 1,994,841 Thomas Mar. 19, 1935 2,518,895 Jacobsson et al Aug. 15, 1950 2,570,899 Wolf c. Oct. 9, 1951 2,618,322 Conta et al. Nov. 18, 1952