Wrapped thermal torch and method

A consumable thermal torch includes inner and outer casings having a first gas flow passage defined therebetween. At least one burning rod is received in the inner casing further defining second gas flow passages. Each of the inner and outer casings is a multi-layer wrapped construction facilitating ease of assembly. The wrapped casings are formed with a powder mix including an effective amount of an exothermic adjuvant. The preferred exothermic adjuvant is magnesium. The powder mix and wrapped casings are each welded or brazed to form integral structures. The magnesium content increases the exothermic reaction temperature of the thermal torch to at least 6000.degree. F.

BACKGROUND OF THE INVENTION 
This invention pertains to the art of thermal torches and more particularly 
to consumable thermal torches or lances. The invention is particularly 
applicable to an oxygen lance typically employed for boring, cutting, 
burning, and the like of hard base materials and will be described with 
particular reference thereto. However, it will be appreciated that the 
invention has broader applications and may be advantageously employed in 
other environments and applications. 
Commonly owned U.S. Pat. No. 4,114,863, which is hereby incorporated by 
reference, generally describes the background of a thermal torch in which 
hard base materials such as ferrous metal, slag, concrete and the like may 
be pierced or cut through due to the rapid, exothermic oxidation of iron 
in the presence of oxygen. Oxygen is supplied under pressure to one end of 
the thermal torch and is ignited at the other end for thermic reaction 
with the base material. Control of the pressure and amount of oxygen 
release from the ignited end, in turn, controls the thermic reaction of 
the torch for cutting and the like. The thermal torch is consumed by this 
reaction and, therefore, must be replaced from time to time with a new 
length of pipe or tubing. 
U.S. Pat. No. 4,114,863 patent describes a marked improvement in the 
thermal torch art by which the so-called "splatter" problem, as well as 
flame spreading, is controlled. A pair of inner and outer casings define a 
first gas flow passage therebetween while the inner casing includes a 
plurality of elongated burning rods. The burning rods define a series of 
second gas flow passages in the inner casing for the primary thermic 
reaction. The center portion of the thermal torch is burned back 
approximately one half inch from the outer casing whereby the first gas 
flow passage forms a substantially continuous oxygen shield to limit the 
splattering at the thermic reaction site. 
With renewed interest in use of thermal torches, it has been considered 
desirable to increase the temperature at which the thermic reaction takes 
place. An increase in thermic reaction temperature necessarily provides a 
wider spectrum of materials which may be cut. Additionally, a simplified 
method of forming the oxygen lance is always desired. Accordingly, the 
subject invention creates the highest exothermic reaction known in the 
industry through the enhancement of the benefits provided by the 
above-noted patented structure. 
SUMMARY OF THE INVENTION 
In accordance with the invention, a consumable thermal torch comprises a 
hollow outer casing having an inlet end, a discharge end, and a generally 
smooth inner wall containing or having in contact therewith an effective 
amount of an exothermic adjuvant. A hollow inner casing also has an inlet 
end, a discharge end, and a generally smooth outer wall. An outside cross 
sectional dimension of the inner casing is less than the inside cross 
sectional dimension of the outer casing defining a first gas flow passage 
substantially surrounding the inner casing. At least one rod is closely 
received in the inner casing and extends between the inlet and discharge 
ends thereof. The rod has a cross-sectional dimension less than the inner 
cross sectional dimension of the inner casing defining a second gas flow 
passage therebetween. 
In accordance with a further aspect of the invention, the inner casing also 
contains or has in contact therewith an effective amount of an exothermic 
adjuvant. 
In accordance with another aspect of the invention, the inner and outer 
casings are planar constructions wrapped and brazed together into a 
multi-layer configuration with a powder mix having the specified magnesium 
content therein. 
In accordance with another aspect of the invention, the burning rods may be 
of steel or aluminum composition. 
In accordance with a method of forming the thermal torch, first and second 
generally elongated, planar sheets have a filler material spread on a 
predetermined portion thereof. The filler material includes approximately 
2% magnesium and the sheets are rolled about a generally longitudinal 
axis. The rolled sheets form a multi-layer construction that is welded 
together and the first rolled sheet is inserted into the second rolled 
sheet. 
A principle advantage of the subject invention resides in the ability to 
create the highest exothermic reaction known in the industry. 
Another advantage of the invention resides in the simplified construction 
of the thermal torch. 
Still other advantages and benefits of the invention will become apparent 
to those skilled in the art upon a reading and understanding of the 
following detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings wherein the showings are for purposes of 
illustrating the preferred embodiment of the invention only and not for 
purposes of limiting same, the FIGURES show a thermal torch or lance A 
comprised of an outer sleeve or casing B and an inner sleeve or casing C. 
A plurality of fuel or burning rods D are closely received in the inner 
casing. 
More particularly, and with reference to FIG. 1, a first generally planar 
sheet E has a rectangular conformation of predetermined length and width. 
The planar sheet has a minimum thickness whereby the sheet is sufficiently 
deformable for rolling about a generally longitudinal axis l. The 
generally planar sheet E may be formed of an appropriate material, such as 
sheet steel or the like, that generally retains its form upon deformation 
into a generally cylindrical configuration. The cylindrical configuration 
has a preselected diameter d that will vary depending on whether the sheet 
forms the inner casing C or the outer casing B of the thermal torch 
assembly. Therefore, as is apparent, the inner and outer casings are both 
formed from similar planar sheets E and, in the following discussion, the 
description of either the inner or outer casing will be equally applicable 
to the other casing unless specifically noted otherwise. 
A powder mix 14 is a conventional hydrogen braze mix to which an exothermic 
adjuvant, which in this case is approximately 2% magnesium, has been 
added. The addition of the exothermic adjuvant, i.e., magnesium, to the 
conventional braze mix composition enhances the thermic reaction results 
to achieve an increased temperature. The mix is spread over a preselected 
portion of a first surface 16 of the planar sheet E. The preselected 
portion is generally substantially less than the full surface area of the 
first surface 16 whereby the planar sheet, when rolled into its 
cylindrical configuration, disposes the powder mix between radially 
adjacent layers 18, 20. 
Typically, each wrapped tubing or casing B, C is at least double-wrapped to 
provide sufficient structural strength to the assembly. Once the sheet has 
been rolled into cylindrical or tubular form, individual radial layers 18, 
20 are integrally joined by welding. Welding is a generic term that covers 
the joining of metals by the application of heat. More particularly, a 
group of welding processes wherein coalescence is produced by heating to a 
temperature above 800.degree. F. and by using a suitable filler metal 
having a melting point below that of the base metals is generally defined 
as brazing. The selection of the material of construction of the planar 
sheet E maintains the radial layers in a fixed relative position during 
heating and cooling of the assembly. A predetermined brazing process is 
selected that provides the most advantageous temperature, heat 
distribution, and rate of heating and cooling with respect to the 
properties of the base metal and filler material. 
The inner and outer casings are, thereby, formed by the above process such 
that the brazed casings include a fusion material having magnesium, or in 
other situations copper or the like, disposed therein. The multi-layered 
outer casing B has a first or inlet end 30 and a second or discharge end 
32 axially spaced therefrom. An inner diameter surface 34 is generally 
smooth to form the outer annular surface of a gas flow passage as will be 
described hereinbelow. 
The inner casing C similarly includes a first or inlet end 40 and a second 
or discharge end 42 axially disposed therefrom. The inner casing 
necessarily has an outer diametrical dimension less than the inner 
diametrical dimension of the outer casing B and the inner and outer 
casings are generally coextensive along their lengths. The outer 
circumferential surface 44 of the inner casing is spaced from the smooth 
inner diameter wall 34 of the outer casing defining a first gas flow 
passage 50 therebetween. The first gas flow passage extends from the inlet 
ends 30, 40 to the discharge ends 32, 42 and is substantially 
circumferentially continuous between the inner and outer casings. As 
illustrated in FIG. 2, the inner and outer casings are generally axially 
aligned at their inlet ends while the discharge ends are axially spaced 
from one another. The inner and outer casings may be concentrically 
arranged or, alternatively, the casings may be off-center defining a 
generally crescent shaped first gas flow passage 50. In either 
arrangement, the first gas flow passage substantially encompasses the 
inner casing. The relative positioning between the inner and outer casings 
is maintained by a plurality of detents 52 that extend radially inward 
from the outer casing B to abutting engagement with the inner casing. 
Conventional metal working techniques may be used to form the detents and 
maintain the inner and outer in a substantially space relation. The 
detents are axially and circumferentially arranged at spaced intervals 
along the thermal torch in order to provide sufficient support as the 
torch is consumed. 
A plurality of burning rods D are closely received within the inner casing. 
Typically, the burning rods are made of a composition of metal that has a 
high quantity of aluminum or steel, these compositions chemically fueling 
the reaction at the discharge end of the thermal torch. The burning rods 
are illustrated as of generally cylindrical conformation although it is 
appreciated that other cross sectional conformations may be used with 
equal success. Positioning of the burning rods within the inner casing 
defines a plurality of second gas flow passages 54 interposed between the 
burning rods and inner casings in addition to the interstices between the 
burning rods themselves. 
As is well known, a pressurized source of oxygen is supplied to the inlet 
end of the thermal torch and the discharge end is ignited. Once ignited, 
combustion is self supporting through the continuous supply of oxygen so 
that a cutting flame is directed axially outward from the torch toward an 
associated workpiece. The oxygen flowing through the second gas flow 
passages 54 reacts with the burning rods and inner casing to form the 
primary thermic reaction site. Since the primary thermic reaction site is 
centered between the burning rods and the inner casing C, these components 
will be consumed at a slightly faster rate than will the outer casing B. 
Thus, as illustrated in FIG. 2, the discharge end of the inner casing and 
the burning rods are axially spaced inward from the discharge end of the 
outer casing B. 
The first gas plow passage 50 provides a gas curtain or shielding effect 
for the primary thermic reaction. The shielding effect provided by the 
first gas flow passage thus reduces splattering that was prevalent in 
other construction. It is apparent that the substantially continuous 
passage between the inner and outer casings promotes the shielding effect. 
Additionally, the gas curtain offers the additional feature of confining 
the flame F into a bullet-like configuration that focuses and intensifies 
the thermic reaction. Precise, narrow cuts are thereby formed with the 
thermal torch. 
The presence of an exothermic adjuvant in the fusion brazed casings creates 
an exothermic reaction that facilitates a higher temperature than 
previously attained in the industry. In this regard, as used herein the 
term "exothermic adjuvant" is intended to mean any metal which is 
different than that from which the concerned casing is fabricated, which 
when oxidized together with such casing results in a higher temperature 
than realized when the casing is oxidized in the absence of such metal. 
Copper and/or magnesium are excellent exothermic adjuvant materials. 
However, other metals and/or alloys may be employed, provided the desired 
results are achieved. When magnesium is employed, a temperature of 
6000.degree. F. or greater is readily achieved and allows vaporization of 
substances that cannot withstand such a temperature magnitude. The thermic 
reaction is easily controlled by regulating the amount of the exothermic 
adjuvant, which preferably is magnesium, and/or copper, in the powder mix. 
A fusion mix containing from an effective amount up to about 2% (by 
weight) magnesium is considered ideal. 
The invention has been described with reference to the preferred and 
alternative embodiments. Obviously, modifications and alterations will 
occur to others upon a reading and understanding of this specification. It 
is intended to include all such modifications and alterations in so far as 
they come within the scope of the appended claims or the equivalents 
thereof.