Self-Extinguishing burning bar

A metallic pipe may be used as a burning bar if the pipe contains wires. The wires are usually steel but may be combinations of steel wires, aluminum wires, magnesium wires and the like. To use the burning bar one end is heated to at least red hot condition. Oxygen is then pumped down the pipe and the pipe then produces a self-sustaining high temperature, high heat flame. A burning bar may be used for demolition and similar uses. In this improved burning bar, the wires within the pipe are arranged so that the wires do not extend the full length of the pipe. There is a portion of the pipe adjacent to the end of the pipe held by the operator which does not contain any wires. The pipe is thus self extinguishing at the point where the wires cease thereby providing safety to the operator and economic advantages.

FIELD OF THE INVENTION 
This invention relates to a cutting torch and in particular, a torch 
comprising a pipe which will gradually burn off with a flame when oxygen 
is supplied. 
There is a commercial need for relatively large capacity cutting implements 
which may be used to cut relatively large bodies such as rock, solidified 
ore, cast iron minerals in the bottom of furnaces and refractory materials 
including furnaces, smelters and the like. Burning bars of this type are 
well-known. Typically the burning bar includes a metallic pipe, typically 
iron or steel, through which oxygen may be pumped. In order to create a 
sufficiently hot flame the pipe is supplied with other burnable material 
such as metallic wires. 
Varying the metallic nature of the wires can produce improved thermal 
output. One example is U.S. Pat. No. 3,260,076 issued 1966 to Humberg. 
Humberg suggests the use of a steel pipe which is filled with a bundle of 
wires. The filling of the pipe may comprise a magnesium alloy core 
surrounded by a number of fusible steel wires. Humberg teaches that the 
flame produced by such a burner pipe is of such a temperature that hard 
materials such as basalt, marble, ore and fire-clay slags as well as cast 
iron and concrete bodies can be cut or severed within a relatively short 
period of time. 
With existing burning bars of the type disclosed in Humberg the bar 
comprises a convenient length of pipe with wires extending through the 
length of the bar. In order to ignite the bar, the bar is first connected 
to a source of oxygen so that the oxygen can flow axially along the pipe. 
The open end of the bar is heated until the pipe wall and the wires 
contained within the pipe are ignited. Then the flow of oxygen is 
commenced and the oxygen flow maintains a flame which may be very hot and 
which may produce a very substantial quantity of heat, in fact, sufficient 
to melt large bodies of rock and ore. 
U.S. Pat. No. 5,458,696 issued October, 1995 and assigned to Southwind 
Enterprises Inc. discloses a process for cutting large blocks of metals 
and breaking up refractory structures by means of a very high temperature 
flame using burning bars of this type. In U.S. Pat. No. 5,468,696 the bar 
to be used for such process contains rods of mild steel and aluminum 
within the pipe. 
As will be well understood by those familiar with such burning bars, the 
bar is consumed by the flame. Thus, the bar starts out at a given length 
and is consumed with the flame becoming closer and closer to the end of 
the pipe and the source of supply of oxygen. Because the temperature of 
the flame is high and because the quantity of heat given off by the 
burning bar is significant there develops a safety issue in how close the 
flame would be allowed to approach the operator. With bars which have been 
made heretofore, the choice of when the operator ceases using the bar is a 
matter of individual choice up to the operator. When the operator decides 
that the existing bar is now sufficiently short, he extinguishes the flame 
by turning off the oxygen supply. Depending upon the judgment of the 
operator a shorter or longer stub of bar may be left when a decision is 
made to extinguish the bar. 
In accordance with the present invention, a burning bar of the type 
discussed above is self-extinguishing. The burning bar comprises a tubular 
metallic conduit having a length L.sub.1 and is intended for use with a 
flow of oxygen containing gas intended to flow axially along the conduit. 
The conduit contains a bundle containing a plurality of metallic wires 
with the bundle of wires arranged so that one end of the bundle of wires 
is located adjacent a first end of the conduit. The bundle of wires has an 
installed length of L.sub.2. In the burning bar of this invention, L.sub.2 
is less than L.sub.1. 
Further, in accordance with this invention, an improved method for 
self-extinguishing a burning bar comprises providing a tubular metallic 
conduit having a length L.sub.1 between first and second ends. A bundle of 
metallic wires is provided within the conduit with the bundle of wires 
having one end adjacent the first end of the conduit. The bundle of wires 
has an installed length of L.sub.2 and L.sub.2 is less than L.sub.1. The 
method further comprises supplying an oxygen containing gas to flow within 
the conduit toward the first end of the conduit at a rate at least as 
great as required to support continuous combustion of the pipe and wires. 
The gas flowing at the aforesaid rate extinguishes combustion of the 
conduit when the conduit and bundle of wires have burned back a distance 
substantially equal to L.sub.2 from the first end of the conduit.

FIG. 1 illustrates a burning bar generally at 10. The burning bar 10 
includes a steel pipe 12 and a wire bundle 14. The steel pipe 12 comprises 
a first end 16 and a second end 18. The wire bundle comprises a first end 
20 and a second end 22. 
The burning bar shown in FIG. 1 has a length between first and second ends 
16 and 18 of L.sub.1. The wire bundle has a length between first and 
second ends 20 and 22 of L.sub.2. From reference to FIG. 1 it will be 
observed that L.sub.2 is considerably shorter than L.sub.1. This leaves a 
portion of the steel pipe 12 adjacent second end 18 open; that is, having 
no wires within that portion. The length of this portion L.sub.3 is equal 
to L.sub.1 -L.sub.2. 
In use, the burning bar 10 is to be connected to a source of oxygen. To 
facilitate the connection, the burning bar is provided with a thread 24 
adjacent second end 18. The burning bar may be then threaded into a 
fitting 26 having a complimentary thread pattern. The fitting 26 may then 
be connected to a source or supply of oxygen which is not shown in the 
Figure. If desired, the fitting 26 may have handles and/or valves to 
facilitate handling the burning bar in use and to facilitate controlling 
the flow of oxygen. The pipe 12 serves as a conduit for the flow of oxygen 
axially along the pipe to the first end. To facilitate the flow of gas, 
the wire bundle has sufficient open space so it permits relatively free 
flow of gas. 
While the term oxygen has been used herein, it is not necessary that the 
bar of this invention be utilized with pure industrial oxygen. Any gas 
which will support combustion may be used. 
As shown in FIG. 2, the burning bar 10 is packed with the bundle of wires 
14. Advantageously the bundle of wires includes a mixture of steel wires 
28 and aluminum wires 30. A mixture of aluminum and steel wires provides 
for a greater output of heat. To further facilitate maintaining the wires 
in the burning bar, the burning bar may be crimped as indicated at 32 at 
approximately a distance L.sub.2 from the first end 16 of the steel pipe. 
The crimp 32 which is adjacent the second end 22 of the wire bundle serves 
to further hold the wire bundle in place and also provides an external 
visual indication of the location of the end of the wire bundle. 
In order to use the burning bar of FIG. 1, the burning bar is connected to 
the fitting 26. The end 16 of the steel pipe which coincides with the end 
20 of the wire bundle is then heated. Suitable sources for heating may be 
oxyacetylene torches or pools of molten metal if available, or other 
readily available sources of significant heat. Once the end of the bundle 
is raised to near combustion temperatures, oxygen is turned on to flow 
through the fitting and axially along the pipe, through the wire bundle. 
When the oxygen reaches the hot end, the oxidation reaction with the metal 
will occur and produce a flame as well as a large quantity of heat. The 
oxygen flow rate to maintain combustion involves providing enough oxygen 
to support combustion of both the wall of the steel pipe 12 and all of the 
wire bundle 14. Flow rates will usually be above this minimum level. As 
combustion proceeds, the wall of the steel pipe 12 as well as the metal of 
the wire bundle will be consumed and the area of combustion will gradually 
move toward the second end 18 of the steel pipe. 
As the pipe and wire bundle is consumed, eventually the area of combustion 
will become adjacent the second end 18 of the wire bundle 14. As the area 
of combustion reaches the second end 18 of the wire bundle 14 there will 
occur an instant in which the flow of oxygen will either consume the last 
of the wire bundle or discharge small fragments of the ends of the wires 
forming the wire bundle out of the steel pipe. After the last of the wire 
bundle has been used up the flow of oxygen which previously had been 
sufficient to maintain combustion of the pipe and the wires now represents 
a substantial excess as only the wall of the steel pipe remains in active 
combustion. It has surprisingly been realized that without the wire bundle 
within the burning bar, the steel pipe will not maintain combustion even 
with a flow of oxygen. Rather, there is insufficient material in active 
combustion to maintain the combustion. Rather, the material cools to the 
point where the metal of the pipe wall no longer undergoes rapid oxidation 
and the combustion stops. This produces a "leftover" length of empty 
conduit having a length L.sub.3 which is about equal to L.sub.1 -L.sub.2. 
Once the wire bundle has been consumed by the oxidation process, the bar 
will not burn any further. Thus, the burning bar becomes 
self-extinguishing. Accordingly, it is possible to design the point at 
which the bar will become self-extinguishing under the flow of oxygen 
which was originally required to maintain combustion. The designer is free 
to choose the relative proportions of the lengths L.sub.1 and L.sub.2 to 
establish the dimension L.sub.3 (i.e. L.sub.1 minus L.sub.2) at which the 
flame will go out and the process will be stopped. 
From a safety point of view, it has been determined that the flame should 
be allowed to proceed no closer than 18 inches to the end 18 of the steel 
pipe. This then leaves 18 inches of space between the end of the steel 
pipe and the intense heat generated by the bar when the combustion process 
stops. 
A further advantage of the burning bar illustrated is that there is an 
economic saving arising from use of a wire bundle of length L.sub.2 which 
is shorter than L.sub.1. As it is desirable for safety reasons that the 
bar extinguish at least 18 inches from the end 18, then the wire bundle in 
conventional bars which extends to second end 18 is not consumed. 
Particularly when the wire bundle comprises a mixture of metals which may 
be more expensive, including not only steel wires but also aluminum wires 
or other alloys, significant savings can occur by not utilizing wires in 
the portion of the bar which is not consumed. It has been found that most 
preferably that L.sub.3, the difference between L.sub.1 and L.sub.2 is 
preferably from about 20 inches to about 30 inches. This provides the best 
compromise between safety and economy. 
EXAMPLE 1 
A burning bar in accordance with the invention was constructed utilizing a 
mild steel pipe of outside diameter 0.976 inches and inside diameter 0.750 
inches. The pipe had an overall length of 10 foot 6 inches. A bundle of 
wires was pulled into the pipe. The bundle of wires comprised mild steel 
rods having 0.125 inch diameter and aluminum rods having 0.12 inches 
diameter. The aluminum content of the wires packed into the pipe is 
approximately 31 wt % of the bundle of wires. The bundle of wires was 8 
feet 6 inches long. The bundle of wires extended from a first end of the 
pipe toward the other end leaving approximately two feet of pipe without 
any wires therein. The pipe was crimped adjacent the end of the wire 
bundle that is about two feet from second end of the pipe. The second end 
of the pipe was connected to a source of commercial oxygen. The first end 
of the burning bar was then heated to red hot and oxygen flow commenced. 
The flow rate was adjusted to provide continuous combustion. The bar 
burned and was consumed until the area of combustion of the bar was 
approximately two feet from the second end of the pipe. At that point the 
combustion ceased even though no change was made in the oxygen flow. When 
combustion stopped the oxygen flow was stopped. The bar was examined and 
it was noted that the remaining length of bar was approximately two feet 
long and did not contain any of the bundle of wires. 
In a subsequent test, the end of a steel pipe was attached to a source of 
oxygen to flow oxygen axially along the pipe. The other end of the pipe 
was heated to red hot condition by placing the end of the pipe in a molten 
pool of metal. Regardless of the quantity of oxygen flowing within the 
pipe, the pipe did not self-sustain combustion. This test showed that 
regardless of the quantity of flow of oxygen axially along the pipe, a 
hollow pipe will not self-sustain combustion without continual additional 
supply of thermal energy. 
In accordance with this invention, a burning bar thus comprises a 
self-extinguishing feature. The bar can be burned by the operator back to 
the design point. Once the design point is reached the bar will 
self-extinguish. The scrap then left is a hollow steel pipe without any of 
the internal bundle of wires. The design point can be established anywhere 
along the length of the bar by arranging a length of the bundle of wires. 
The bundle of wires are advantageously pulled into the pipe and thus are 
straight. There is however no requirement that the individual wires of the 
bundle be parallel to the pipe axis. If desired or convenient, depending 
upon the supply of wires available, the wires could be crimped, kinked or 
coiled or the like. It is the presence or absence of the wires which 
causes the combustion to cease. In this description and claims the length 
of the bundle is referred to as the installed length as the length of the 
individual wires and their configuration is not a limiting feature of the 
invention. 
This invention has been described in connection with a preferred 
embodiment. Various modification may be made by those skilled in the art. 
The invention is not to be limited to this preferred embodiment but only 
by the scope of the following claims.