[Illustration: Figure 20.--High Pressure Torch Head]
With a true high pressure torch (Figure 20) the gases are used at very
nearly equal heads so that the mixing before ignition is a simple matter.
This type admits the oxygen at the inner end of a straight passage leading
to the tip of the nozzle. The acetylene comes into this same passage from
openings at one side and near the inner end. The difference in direction of
the two gases as they enter the passage assists in making a homogeneous
mixture. The construction of this nozzle is perfectly simple and is easily
understood. The true high pressure torch nozzle is only suited for use with
compressed and dissolved acetylene, no other gas being at a sufficient
pressure to make the action necessary in mixing the gases.
_Medium Pressure Torches._--The medium pressure (usually called high
pressure) torch (Figure 21) uses acetylene from a medium pressure generator
or from tanks of compressed gas, but will not take the acetylene from low
pressure generators.
[Illustration: Figure 21.--Medium Pressure Torch Head]
The construction of the mixing chamber and nozzle is very similar to that
of the high pressure torch, the gases entering in the same way and from the
same positions of openings. The pressure of the acetylene is but little
lower than that of the oxygen, and the two gases, meeting at right angles,
form a very intimate mixture at this point of juncture.
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