Title:
OUTER NOZZLE FOR THE CUTTING HEAD OF A FLAME CUTTER
United States Patent 3675852


Abstract:
A cutting head for a flame cutter feeds oxygen through a central nozzle and a mixture of oxygen and natural gas through a ring of peripheral nozzles that converge at a point on the axis of the oxygen stream at an angle of 25° to 45°. The peripheral nozzles are fed from an annular mixing chamber at least five times the volume of the inner nozzle, and the total cross-sectional area of the peripheral nozzles is from two to eight times the cross-sectional area of the discharge orifice of the inner nozzle.



Inventors:
Hajduk, Jeno (Budapest, HU)
Katai, Mihaly (Budapest, HU)
Application Number:
05/076007
Publication Date:
07/11/1972
Filing Date:
09/28/1970
Assignee:
NIKEX NEHEZIPARI KULKERESKEDELNI VALLALAT
Primary Class:
Other Classes:
239/424, 239/429
International Classes:
F23D14/54; (IPC1-7): F23D11/16
Field of Search:
239/422,424,428,429,423,419.3,418
View Patent Images:
US Patent References:
3565345PRODUCTION OF AN ARTICLE OF HIGH PURITY METAL OXIDE1971-02-23Moltzan
1575661Sign1926-03-09Beanes
1460662Burner for the autogenous cutting of metals1923-07-03Drager et al.
1119916N/A1914-12-08Willis



Primary Examiner:
King, Lloyd L.
Claims:
What we claim is

1. A cutting head for a flame cutter, comprising a mixing chamber defined between an inner nozzle for oxygen and an outer nozzle for a gas mixture, the outer nozzle having an end wall containing a central bore receiving the discharge end of the inner nozzle, the end wall also containing auxiliary bores whose longitudinal axes intersect the longitudinal axis of the central bore outside the nozzle, the angle between the longitudinal axis of each auxiliary bore and the longitudinal axis of the central bore being between 25° and 45°, the inner surface of the outer nozzle being cylindrical over at least 80 percent of its length, and the volume of the mixing chamber being at least five times the volume of the inner nozzle, said longitudinal axes intersecting at a common point, the total cross-sectional area of the auxiliary bores being from two to eight times the cross-sectional area of the discharge orifice of the inner nozzle.

Description:
The invention relates to an outer nozzle for the cutting head of a flame cutter for flame cutting using methane and oxygen or propane-butane gas and oxygen.

Flame cutting, which is effected by a cutting torch, finds application to reducing metals to smaller pieces in a very wide range of industrial work. In the cutting head of the flame cutter are provided an outer nozzle and the inner nozzle. The conventional acetylene-oxygen mixture, issuing through the orifice of the outer nozzle and ignited, heats up the metal to the oxidation temperature, then a jet of pure oxygen is directed at the metal through the inner nozzle, and this oxidizes the not metal and converts it into liquid slag ahead of the oxygen jet. The slag thus produced is expelled from the cut, by the force of the oxygen jet.

Cutting heads are already known wherein the inclined passages of the inner nozzle wreath are so formed that the gas flowing out through the passages comes in contact with the bounding surface of the oxygen jet and imparts to it a rotary motion thus ensuring a better intermixing of the gas with oxygen, which enhances the efficiency of cutting.

If, however, methane or propane-butane gas is used instead of the dissolved acetylene as the gas, then the flame cutting cannot be carried out with the cutting heads of the known flame cutters, because the flame value of these gases is considerably lower than that of acetylene. The flame value of methane is only 8700 calories as compared with 17,000 calories for acetylene.

The invention is based on the problem of providing for the said purpose a cutting head whereby, instead of acetylene, methane of propane-butane gas can also be used for cutting metals, more particularly steel sheet, by exchanging the outer nozzle of the cutting head, while the remaining apparatus is retained. A further problem consists in reducing the gas consumption and at the same time increasing the cutting speed and operational safety.

The invention stems from the finding that flame cutting can be carried out with a gas of lower flame value as well as with a gas of higher flame value, provided that before the gas mixed with oxygen is discharged the intermixing is made more intimate and the quantity of the outflowing gas mixture and that of the cutting oxygen is kept in a given ratio to each other.

The invention provides an outer nozzle for the cutting head of a flame cutter, the inner surface of the nozzle being cylindrical over at least 80 % of its length, the nozzle having an end wall containing a central bore and auxiliary bores whose longitudinal axes intersect the longitudinal axis of central bore outside the nozzle, the angle between the longitudinal axis of each auxiliary bore and the longitudinal axis of the central bore being between 25° and 45°.

The invention also provides a cutting head for a flame cutter, comprising a mixing chamber defined between an inner nozzle for oxygen and an outer nozzle for a gas mixture, the outer nozzle having an end wall containing a central bore receiving the discharge end of the inner nozzle, the end wall also containing auxiliary bores whose longitudinal axes intersect the longitudinal axis of the central bore outside the nozzle, the angle between the longitudinal axis of each auxiliary bore and the longitudinal axis of the central bore being between 25° and 45°, the inner surface of the outer nozzle being cylindrical over at least 80 percent of its length, and the volume of the mixing chamber being at least five times the volume of the inner nozzle.

It has been established by measurements made during the tests that the gas consumption assumes a very advantageous form when bores according to the invention are used. With an annular nozzle only a quarter of the preheating flame usefully heats up the material at the position to be cut, while three quarters of the flame needlessly heats other parts of the workpiece. This wastage can be considerably reduced by the use of bores according to the invention and the gas consumption can drop by up to 20 percent. By the correct arrangement of the bores and their appropriate dimensioning it is also possible to ensure a 10 percent increase in cutting speed.

The correct choice of the angle enclosed between the center line of the bores and the longitudinal axis of the cutting head makes possible the optimal setting of the distance between the flame cutter and the workpiece, whereby is enhanced in addition to the working safety also the useful life of the flame cutter.

The outer nozzle according to the invention can be made just as the conventional outer nozzle, in several stock sizes according to the inner nozzle of the flame cutter. The nozzle according to the invention can be used for the cutting head of a flame cutting apparatus as well. In this way it can be achieved that the flame cutter moved along a predetermined path cuts the workpiece according to the desired profile by using methane or propane-butane gas.

Flame cutting with methane or propane-butane gas is very economical, not only because of its much lower price as compared with the dissolved acetylene, but also because of the practically unlimited supply of these gases.

Methane is usually available in most works. The properties, supply and handling of the propane-butane gas are substantially more convenient than those of dissolved acetylene, which enables the cutting to be done at the work place.

It has been established by tests on the material, carried out in the course of experiments, that the surface of the cut piece is not only smoother than the surface of the piece cut with the conventional oxy-acetylene torch, but also the structure of the surface is more uniform and freer from flaws.

The invention is particularly explained below in an example of embodiment. The accompanying drawings show in

FIG. 1 a cutting head in longitudinal section; and in

FIG. 2 the outer nozzle on an enlarged scale.

The length and the thread neck of the outer nozzle 1 are identical with those of the ordinary conventional outer nozzle. The outer nozzle 1 is screwed onto an inner nozzle 3 and a mixing chamber 2 is defined between the two. There is a tight fit between the outside walls of the discharge orifice 9 of the inner nozzle 3 and a bore 8 drilled in the end wall 10 of the outer nozzle 1. The longitudinal axis 11 of the outer nozzle 1 and the longitudinal axis of the inner nozzle 3 are coincident. Bores 4, inclined to the longitudinal axis 11 are also formed in the end wall 10 of the outer nozzle 1. The center lines 12 of these bores 4 intersect the longitudinal axis 11 of the inner nozzle 3 outside the cutting head at a common point 13 which, in operation, coincides with the surface of the material to be cut. The angle α sub-tended by the center lines 12 of the bores 4 lies between 50 and 90°, and the total cross section of the bores 4 is two to eight times the cross-sectional area of the outflow orifice 9 for the cutting oxygen.

The outer nozzle 1 is screwed into the cutting head in the conventional way. Connected to the cutting head are an oxygen pipe 6 and a mixing pipe 7. Cutting oxygen is fed through the oxygen pipe 6.

The inside walls of the outer nozzle 1 are cylindrical over at least 80% of its length, owing to which the mixing chamber 2 is cylindrical. The volume of the mixing chamber 2 is at least the fivefold, preferably ten- to twelve-fold, of the volume of the inner nozzle 3.

The cutting head works in the following way:

The methane or propane-butane gas flowing through the mixing chamber (not shown), which is known as such, provided in the handle of the flame cutter mixes with oxygen, and this mixture reaches the mixing chamber 2 through the mixing pipe 7. The bores 4, formed in the end wall 10 of the outer nozzle 1, constitute the discharge orifices for the gas mixed with oxygen. Since the portions of the end wall 10 between the bores 4 offers a resistance to flow from the mixing chamber 2, an enhanced intermixing of the gas occurs in this chamber.

By suitably choosing the diameter of the bores 4 an optimal cut, corresponding to the thickness of the iron sheet (plate) to be cut, can be ensured. Tests have shown that an optimal cutting result is obtained if the total cross section of the bores 4 is two to eight times the cross section of the discharge orifice of the cutting oxygen. From this the number and the diameter of the bores can be calculated.

Owing to the fact that the angle α enclosed between the bores 4 lies between 50 and 90°, the point of intersection 13 of the center lines 12 of the bores 4 falls at a well-defined place upon the surface of the material to be cut, as a result of which only that part of the workpiece is heated which actually needs to be cut. In this way the gas consumption needed for the cutting is reduced, the cutting speed is increased and the structure of the surface of the cut piece becomes more uniform and freer from flaws, as compared with cutting using conventional cutters.