Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a welding torch which is
useful for the heating or welding of metals.
In my Australian Patent 460,066 I described and claimed
5. a torch attachment for the attachment to a hand piece bend
of a torch, the attachment containing a mixing chamber
extending in a downstream direction from the adaptor
and terminating in a nozzle, the mixing chamber being at
least eight times its diameter and the chamber and
10. nozzle walls being free of abrupt steps so that gas passing
therethrough was in a substantially non-turbulent streamline.
The torch attachment disclosed in that specification had
a characteristic of providing a concentrated higher temperature
heat pattern than previously proposed torches, and because of
15. this characteristic has proved to be economical in gas usage.
Independent tests undertaken by the University of Adelaide,
showed gas savings totalling about 8u~. However, there
are certain difficulties which are encountered, prohably the
most serious of which is that the handpiece becomes cumbersome
20. and awkward to use due to a relatively long mixing chamber
attached to an existing torch, and one ob~ect of this ;nvention
is to provide improvements wherein a higher temperature and more
concentrated heat pattern can b~ achieved than with the usual
existing torches, but with a much neater and more convenient
25. hand piece.
The closest prior art known to t~ Applicant is the U.S.
Patent No. 1,418,245 issued to FOUCHE wherein oxygen and acet-
ylene are mixed in forwardly moving annuli, but the mixed
gases pass straight into a single mixing chamber before issuing
from a nozzle.
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Safety demands have a great influcnce on welding torch
configuration. "Blow-back" is a phcnomenon caused by a flame
front travelling back through the nozzle aperture and into the
mixing chamber of the torch. In torches as presently used,
5. more oxygen is re~uired than acetylene (to satisfy the com-
bustijn equation 502+2C2H2^-~CO2+2~l2O), and it is customary for
a higher pressllre of oxygen to be used than acetylene. It
becomes possible for oxygen to enter the a~e~ylene hose, and
in order to reduce blow back danger, acetylene is introduced
10. into the mixing chamber of prior art torches through a
plurality of small apertures. However "blow-back" can
result in a small explosion within the mixing chamber, and
instances still occur of explosion damaging the acetylene
gauges, due to combustion within the acetylene hose itself,
15. notwithstanding the existence of the small apertures. It is
another object of the invention to improve the safety of a
torch, such that there ;s less likelihood of "blow-back" extend-
ing into the hose which conveys the combustible gas (the
acetylene hose).
20.
Briefly in this invention a torch is provided with
` components which define a primary mixing chamber of relatively
small volume, a secondary mixing chamber of relatively large
volume, a gas mixture directing aperture the length of which is
25. much greater than its diameter, the directing aperture directing
gas after being mixed in the primary mixing chamber into the
secondary mixing chamber, and a discharge nozzle at the
downstream end of the secondary mixing chamber.
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If the chambers, the directing aperture and the nozzle
are co-axial, and if they are correctly dimensioned, it
becomes possible to use equal pressures for oxygen and acety-
lene, and thereby reduce danger of oxygen entering the acety-
5. lene hose. It has also been found possible to achieve
higher temperatures and more concentrated heat than was
achieved with the torch described in said patent 460,066.
If the torch is arranged to have a central stream of oxygen
directed into the primary mixing chamber, and this entrains an
10. annulus of acetylene, then the further oxygen required and
supplied from atmosphere is entrained by the smooth-flowing
non-turbulent gases issuing from the nozzle, into the
acetylene-rich annulus. Furthermore, the gas surrounding the
welding zone comprises steam, nitrogen and carbon dioxide,
-~ 15. so that corrosion near the weld zone is largly inhibited.
Still further, a phenomenon is observed, that a higher
temperature exists at the centre of the flame than in prior
- art torches, and this is thought to be due to non-uniform
combustion over the cross-section of the flame.
; 20. More specifically, this invention consists of a welding
torch comprising a hand piece, an oxygen conduit in the hand
; piece having connection means at its upstream end for connecting
to an oxygen supply hose, and a tubular oxygen director
at its downstream end, said tubular oxygen director being in
25. gas flow communication with the conduit, a gas mixing structure
comprising at least one mixing member which defines with the
oxygen director, a primary mixing chamber, a combustible gas
conduit in the hand piece having connection means at its
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upstream end for connecting to a combustible gas supply
hose, and walls in the hand piece placing the downstream
end of the gas conduit into gas flow communication with the
primary mixing chamber, the gas mixing structure comprising
5. a gas mixture directing aperture having a length exceedin-~ its
` diameter, and walls defining a secondary mixing chamber ofgreater volume than the primary mixing chamber, a length which
exceeds its diameter, and a diameter which exceeds that of said
~^ gas mixture directing aperture, and a discharge nozzle
10. at the downstream end of said secondary mixing chamber,
said oxygen director, primary mixing chamber, gas mixture
directing aperture, secondary mixing chamber and nozzle all
having a common polar axis.
With this arrangement a stream of oxygen and acetylene
15. (for example) which issues from the nozzle provides a very
smooth flame having a very concentrated high temperature central
portion even though the amount of oxygen used is less than
with a conventional torch. The torch is capable of even
higher speed welding (for the same gas consumption) than the
20. combined torch and attachment described in the specification
of said Australian Patent 460,066. Instead of the
ratio being 5 parts by weight (2 by volume) of oxygen to 2
parts by weight (1 by volume) of acetylene approximately for
perfect combustion, the ratio can be reduced to approximately
25. 1:1 parts by weight (the other oxygen coming from the
surrounding atmosphere), and furthermore the gas usage can be
still further reduced.
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Some operators use wcldil-g torches wit~ ~heir right
hand and others with their le~t hand, and in another aspect
of this invelltion the torch hand piece is provided with swivel
nuts at the upstream ends of tl-e oxygen and gas conduits
5. respectively, valves coupled to the swivel nuts, and hose
unions on the inlet ends of the respective valves. By
relaxing the swivel nuts, the valves can then be rotated and
re-positioned to suit the user.
In another aspect of the invention, the hand piece is
10. provided with a handle through which the oxygen and gas -
conduits pass.
In another aspect of the invention, the hand piece is
provided with a connector block secured to it and having the
gas flow conduits extending through the connector block,
15. the connector block being of relatively small cimension so
that the hand piece may be used as a "pencil torch".
~wo embodiments of the invention are described hereunder -
in some detail with reference to and are illustrated in the
;; accompanying drawings, in which
Fig. 1 is a partly sectional elevation of a welding
torch according to a first embodiment,
Fig. 2 is an "exploded" elevation of the oxygen director,
the gas mixing structure and the nozzle,
25. Fig. 3 is a sectional elevation showing said elements
assembled, and being drawn to an enlarged scale,
- Fig. 4 is a fragmentary sectional elevation showing twomixing members of the gas mixing structure separated to a~low
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entrainment of air into the secon(lary mixing chamber, and
Fig. 5 is an elevation of a "pencil torch", which is
the second emboclimcnt of the invention.
. In the first embodiment of Figs. l, 2, 3 and 4 a w~l~]ing
torch 10 is provided with a hand piece 11, and at the "heel"
of the hand piece there are provided two unions each designated
12, each with a swivel nut to which is connected a respective
valve, one desigated 13 for oxygen and the other designated
10. 14 for combustible gas (herein simply termed "gas", and usually
intended to mean acetylene although butane and other gases
can also be used Wl th this invention). The swivel nut
arrangement enables each valve to be rotated to occupy a
position most convenient for the user, this being a very
15. desirable feature for arranging the hand torch to be used
by right or left hand operators.
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In this embodiment, the hand piece 11 is provided
with a formation such as to make it convenient to be
grasped by an operator's hand, and terminates at the end away
20. from the nut unions in a boss 17. The boss contains a
threaded aperture 18 extending through at an angle with respect
to the longitudinal axis of the han(,~e portion of the hand
piece, and the hand piece contains two conduits, one being an
oxygen conduit 19 at the rear end and the other beinc~ a gas
25. conduit 20 at the front end, the conduits being parallel or
nearly parallel and texminating in the threaded aperture 18
with the oxygen conduit 19 being behind the gas conduit 20.
The conduits may be formed by drilled holes in an otherwise
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solid handle, but a "light weight" handle as illustrated is
usually preferred by operators.
The threaded aperture is threadably engaged by,
firstly, an oxygen director 24, the oxygen director being a
threaded member having a thread 25 extending for portion of
its length, the thread 25 itself being interrupted by walls
which form an annular recess 26. The front or downstream end
of the oxygen director has a stem 27 which is tapered around
its outer periphery, and the stem surrounds a central
10. axially extending oxygen directing aperture 28 which is of
diamter approximately equal to the maximum diameter nozzle
tip which will be used, in this embodiment the diameter being
2.40 millimetres. A plurality of radially extending apertures
29 intersect the rear end of the oxygen directing aperture 28,
15. and open into the annular recess 26, and the arrangement is
such that when the oxygen director is screwed "home", that is
to the base of the threaded aperture 18 in the hand piece
boss 17, the annular recess aligns with the oxygen conduit and
; oxygen will then pass through the oxygen conduit, the annular
20. recess, the radial apertures and into the oxygen directing
aperture to issue therefrom as a high speed stream of relatively
small diameter.
Closer to the mouth or downstream end of the threaded
aperture 18 in the hand piece boss 17 there is a gas mixing
25. structure generally designated 31 and comprising a primary
mixing member 32, the primary mixing member 32 having at its
upstream end a gas diffusing skirt 33 which surrounds the
~ tapered stem 27 and bears at its upstream end against a
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shoulder 34 at the upstream end of the tapered stem 27, but
the gas diffusing skirt has a relatively large diameter
central chamber at its upstream end which constitutes a
primary mixing chamber 35, and into which the small diameter
stream of oxygen passes. A plurality of small diameter
radially extending apertures 37 pass through the gas
diffusing skirt, and the arrangement is such that the space
surrounding the gas diffusing skirt (the outer diameter of
which is less than the thread diameter of the threaded
aperture) is in communication with the downstream end of the
gas conduit 20, whereby the pressure of gas in the gas conduit
and the flow of oxygen combine to entrain gas into the oxygen
stream, but near its outer periphery. Thus, there is some
mixing of the gas and oxygen in the primary mixing chamber,
even through the flow there through is relatively non-turbulent
but it is believed that at this stage at least, the core is
oxygen-rich. It may be noted that this is in direct contrast
with prior art torches many of which have employed complicated
arrangements to ensure thorough turbulence of the gases.
As seen best in Fig. 3, radially extending apertures 37
open into a diverging annular space. In the case of blow-
back, even if oxygen has entered the acetylene hose, danger
of combustion within the hose is reduced by this configuration.
The primary mixing member 32 has a relatively large
diameter primary mixing chamber 35 only at its upstream end,
and this merges into a relatively small diameter parallel
walled aperture which can be regarded as a gas mixture
directing aperture 39 at the downstream end, the gas mixture -
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directing aperture in this embodiment being of the same
diameter as the oxygen directing aperture (2.40 millimeters)
so that the gas mixture which issues therefrom issues as
a relatively small diameter relatively non-turbulent
stream. Its length however is at least five times greater
than its diameter, in this embodiment about 22 millimeters.
This dimension is important and must be adjusted for a torch
of any given dimensions by empirical means to achieve optimum
results. The threaded outer portion of the primary mixing
member 32 projects outwardly from the mouth of the handle,
and this is threadably engaged by a small sleeve 41 which
constitutes an air entrainment sleeve, the air entrainment
sleeve being threaded throughout its length but having a
plurality of radially extending apertures extending there-
through from a shallow groove 42 in its outer surface. The
apertures include three relatively large apertures 43 and
three relatively small apertures 44, this arrangement being
more suitable for limiting incidence of "blow-back" than if
all apertures are of the same size, since it results in
uneven gas mixtures within the torch.
The radially extending apertures 43 and 44 are positioned
slightly downstream of the downstream end of the primary mixing
member 32, but the downstream end of the primary mixing member
32 is provided with a small projecting boss 46 which tapers
towards the issue end when the apertures are opened with
respect to the gas stream issuing from the primary mixing
member, air is entrained with the gas stream as shown in Fig. 4.
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The other or downstream end of the air entrainment sleeve
is threadably engaged by a secondary mixing member 48 of the gas
mixing structure 31, the secondary mixing member 48 having a
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thread extending for most but not all of its length, and
5. the thread is interrupted intermediate its ends by a recess
49 so that an operator can quickly identify when the
secondary mixing member has been unsc~ewed sufficiently for the
air entrainment aperture 43 and 44 to be exposed. The air
entrainment apertures are exposed on]y occasionally, that is
lO. when the torch is required for heating of metal as distinct
from welding of metal, and large areas of relatively low
temperature gas are required to issue from the jet. NOrmally,
however, the secondary mixing member is screwed hard against a
tapered surface 50 which surrounds the boss 46 of the down-
15. stream end of the primary mixing member, and a relatively
large diameter central aperture within the member 48 pro~7ides
a secondary mixing chamber designated 52.
Screwed on to the downstream end of the secondary mixing
member 48 is a nozzle 53, the nozzle 53 having a bore 54 of
20. identica1 diameter to the diameter of the secondary mixing
chamber 52, and the bore terminating in tapered walls 55
which terminate in an outlet jet aperture 56. The bore 55 of
the nozzle 53, the inner walls of the jet aperture 56 and
the bore of the secondary mixing chamber 52 are made as smooth
25. as possible, the smoother the better. In this embodiment the
walls of the bore of the secondary mixing chamber 52 are
burnished to achieve a high degree of smoothness. It has been
found also that the length of the bore which is common to the
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secondary mixing chamber and the upstre~m end of the nozzle
should be related to its diameter, unless th~ bore is very
long. However, for practical purposes it is desirable tha-t
the bore be as short as possible, and should exceed eight times
5- the bore diameter. In this embodiment the bore length is
11.25 x the bore diameter, tha~ is, for a bore diameter of
- 6.4 mm the bore length needs to be approximately 72 mm.
It has been found by experimentation that the bore length
should be an odd mul~iple of 1.25 x the diameter and at
10. least 8.75 x the diameter to achieve the desired mixing condit-
ions. If the bore is increased beyond the 11.25 x diameter
of this embodiment, the criticality of its length progessively
reduces, and results progressively improve, although the improve-
ment is~ 80 slight that in most instances extended lengths are
15. not required. It is also found desirable to control the angle
of convergence of the tapered walls 55 which define the end
of the secondary mixing chamber bore, and in this embodiment
the included cone angle is approximately 54 degress. It
should range between 45 and 65 degrees, but the closer it is
20. taken to 54 degrees, the better the results are likely to
be. This is believed to be related to the deflection of
particles or molecules oE gas Erom the walls of the boreO
Again it has been found for reasons which are not under-
stbod, that the jet diameter of the issuing aperture of the
25. nozzle is critical, and ~or any given torch, a series of
experiments are required to ascertain which diameters are
suitable. In the example of this embodiment, there have been
three satisfactory diameters discovered, one being 0.90
millimeters, the second being 1.30 millimeters and the largest
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being 2.40 millimeters, that is the same diameter as the
diameter of the aperture through the oxygen director and
the first mixing member. Diameters between these diameters -~
have been found to give results which are inferior.
In use, gas at low pressure (about 4 p.s.i. or 28 k.p.a.)
is delivered at equal volumes to the torch, and not in the
theoretically correct 80:32 ratio of oxygen to acetylene, but
the flame temperature is extremely high for a very small
diameter. A blue smooth cone extends for about nineteen mm.
in the case of the smallest tip, twenty nine mm. for the
intermediate tip, and sixteen mm. for the large tip. If
butane and oxygen are used then a 1-1 ratio by volume is
found to work satisfactorily, but the temperature is much lower
than with acetylene.
The primary combustion of the blue cone is known to yield
carbon monoxide and hydrogen, and the secondary combustion
of the surrounding flame to yield carbon dioxide and steam.
However, the surrounding flame is not oxygen-rich, and oxygen
is entrained from the atmosphere by the smooth flowing gases
to form the envelope flame. The quantity of entrained oxygen
is very much greater than the prior art torches, and the
welding takes place under such advantageous conditions that
negligible metal oxidation occurs. This in turn simplifies
welding of difficult metals such as aluminium and magnesium
alloys.
The invention results in such improvements that micro-
welding becomes possible, and in a second embodiment
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(illustrated in Fig. 5) the construction is substantially
similar to the first and similar numbers designate similar
elements, excepting that instead of using a handle as in
the first, the hand piece 11 comprises a gas directing block
5. 60 secured to one side, and near one end, of a mounting
cylinder 61 which takes the place of the boss of the handle
and which is threadably engaged by the oxygen director and
by the primary mixing member. The block 60 is provided
with two small flexihle tubes 62 to hose valves (not shown)
10. and the device can then be held between the fingers in the
manner of a pencil. However, a simple tubular handle 63
is also provided which slips over the device and locks on to
the cylindrical member 6 to provide a handle for hand welding
if this is required.
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