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Reference is made to my copending patent application Ser. No. 728,202,
filed Sept. 30, 1976.
The invention relates to a method and apparatus for applying metal coatings
to metal substrates and is in particular concerned with gas-torch
techniques wherein metal powder is deposited, as for example along an edge
which is ultimately to serve as a cutting edge.
Prior techniques for the gas-torch application of metal coatings to metal
substrates have involved hand-held devices requiring relatively great
skill in manipulation, if acceptable bonding and coating quality are to be
achieved. As a practical matter, there is always a degree of uncertainty
as to just how reliable the coating will be in use, so that testing
procedures are costly and relatively elaborate, depending upon the degree
of assurance desired. The problem is particularly acute for application of
such metal coatings along a particular swath or edge which may undulate or
be non-linearly characterized.
It is therefore an object of the invention to provide an improved method
and means for gas-torch application of metal coatings to metal substrates.
It is a specific object to meet the above object for situations in which
the metal coating is to be applied along a swath in a surface of the
substrate.
It is also a specific object to meet the above objects with virtual
certainty of superior-quality coatings at all times.
It is another specific object to meet the above objects to a degree
permitting the substantial reduction of testing procedures.
A further specific object is to provide an improved method and means of the
character indicated whereby a predetermined metal coating may be applied
to a given substrate, with complete reproducibility of a metal coating of
precisely the same high quality and thickness, from one workpiece to the
next, in a succession of similar workpieces to be treated.
A still further specific object is to meet the above objects for a coated
swath which follows a non-linear course in the substrate surface.
A general object is to achieve the foregoing objects at substantial savings
of expense for materials and labor, in both coating and testing
operations, and with relatively great universality of application, in a
large variety of workpiece configurations.
Other objects and various further features of novelty and invention will be
pointed out or will occur to those skilled in the art from a reading of
the following specification in conjunction with the accompanying drawings.
In said drawings, which show, for illustrative purposes only, a preferred
embodiment of the invention:
FIG. 1 is a simplified view in perspective of apparatus of the invention,
illustratively shown in application to the metal coating of a cutting-edge
region of a harrow "point";
FIGS. 1A, 1B, 1C are simplified fragmentary views in perspective, to
illustrate a variety of different workpieces which may be coated by the
apparatus of FIG. 1;
FIG. 2 is an electrical block diagram of circuitry to operate the machine
of FIG. 1;
FIG. 3 is a graphical presentation to show several coordinated operations,
to the same time base, in operation of the machine of FIG. 1; and
FIGS. 4 and 5 are similar simplified enlarged sectional views of a coated
substrate in the course of a coating application to illustrate operation
of the machine of FIG. 1.
In FIG. 1, the invention is shown in application to an automatic operation
upon a workpiece W, shown in phantom outline as a harrow "point" to which
a swath of coating metal is to be applied by a Torch T along each of two
divergent cutting edges thereof. Generally, each cutting edge will be
straight, but the orientation of these cutting edges with respect to the
vertical plane of symmetry of mounting alignment (e.g., alignment of
mounting to its intended supporting structure) involves complex angle
components. The torch T is shown carried by unitary mechanism including a
floor-mounted frame comprising a base 10 and a fixed upright column 11.
The workpiece W is removably secured to a work holder 12 carried by
unitary mechanism including a floor-mounted frame or stand 13. A control
and monitoring panel 14 is also floor-mounted, upon a pedestal stand 15
and has flexible electrical connection 16 to the torch-mounting unit (at a
junction box 17) and thence, via a further flexible electrical connection
18, to the work-mounting unit. The three stands 10-11, 13 and 14 may of
course all be integrated into a single floor-mounted piece of equipment;
however, I prefer that each of these units shall be separately
floor-mounted as shown, for maximum flexible adaptability to various
particular different job requirements and situations, in that any force
reaction between torch-related and workpiece-related elements is
negligible compared with the mass and relatively immobility of units
10-11, 13 and 14, once set in desired position on a given floor.
The torch-mounting unit includes three orthogonally related guide and drive
systems for universal positioning of the torch T in space. Specifically, a
main slide 20 is vertically guided in ways 21 forming part of column 11;
along these ways, an elongate rack 22 is engaged by pinion means (not
shown) but forming part of a Z-axis drive which includes motor means 23
carried by slide 20. The main slide 20 includes a horizontal arm 24. A
secondary slide 25 is horizontally guided by ways 26 forming part of arm
24; along these ways (26), an elongate rack 27 is engaged by pinion means
(not shown) but forming part of a Y-axis drive which includes motor means
28 carried by slide 25. Columns 29 at the corners of slide 25 mount
another horizontal arm or deck 30, equipped with horizontal ways 31 which
are orthogonal to the ways 26. A third slide 32, which is the ultimate
supporting slide for torch T, is horizontally guided by the ways 31; along
these ways (31) an elongate rack 33 is engaged by pinion means (not shown)
but forming part of an X-axis drive which includes motor means 34 carried
by slide 32. Suitable flexible cables, as at 35 from box 17 to the X-axis
motor 34, will be understood to accommodate interconnection of all motor
drives, and other moving parts including limit switches to be later
described.
The workpiece holder 12 is shown mounted to and extending upwardly from a
turntable 36, journaled in a cradle frame 37 for rotation about a
generally vertical axis, for an azimuth or .theta. component of workpiece
positioning; for the depicted accommodation of harrow points (see also
FIG. 1A), the holder 12 comprises an upstanding column with oppositely
sloping upper flats to which shanks of two harrow points W may be secured,
with their cutting edges symmetrically oriented substantially in a single
plane which is normal to the axis of rotation .theta.. The cradle 37 will
be understood to include motor means (not shown, but suggested by the
legend ".theta.-Drive") whereby mounted workpieces may be driven about the
.theta. axis. Cradle 37 is in turn supported for tilting adjustment about
a second axis, orthogonal to the .theta. axis, being journaled on a
horizontal axis through spaced upstanding arms 38 forming part of the
stand 13; and an .alpha.-Drive motor 39 is shown with pinion connection to
a sector gear 40 for positioning cradle 37 about the horizontal axis of
.alpha.-displacement. The arms 38 are preferably canted forward, as shown,
to place the horizontal axis of .alpha.-tilt close to the forward legs of
stand 13, for more convenient work placement with respect to torch T.
An important feature of the invention is concerned with developing a
predetermined elongate path of metal coating upon a workpiece surface, as
along and immediately adjacent one cutting edge thereof, and in the
circumstance that the width of the desired path exceeds the width of a
single bead that can be deposited by a single pass of the torch across the
workpiece surface. To meet this situation, the torch T and the workpiece W
are subjected to a relatively slow first component of feed motion
governing torch progress along the intended path while also subjecting the
torch T and the workpiece W to a relatively fast second component of
oscillatory motion governing torch displacement generally transverse to
the intended path. These two components of feed motion may be generated by
different combinations of the drives thus far described --for example, for
a straight horizontally oriented harrow point edge that is set parallel to
the X-axis guideways 31, a slow X-drive rate, combined with a relatively
rapid Y-drive oscillation, the latter being at short amplitude of
shuttling reciprocation to thereby cover the width of the intended path.
In the form shown, however, I indicate my preference for use of separate
mechanism 41 to impart oscillating motion to torch T, such mechanism 41
being carried by and effectively part of the X-axis slide 32 but shown
positioned away from ways 31 by an offsetting arm 42.
The functional relationship of torch T to its oscillating mechanism 41 will
be better understood from the schematic showing at the upper left corner
of FIG. 2, wherein a vertical pedestal 43 rises from a horizontal base 44
and provides a vertical axis of pivotal support for the torch body 45.
Torch T includes separate inlets 46-46' for connection to oxygen and
acetylene supplies, via flexible hoses (not shown), and a discharge of
torch products issues from a downwardly and forwardly directed nozzle 47;
electrode 48 is held by an offset arm 48' at fixed spacing from nozzle 47
and is excited, via a flexible lead, by means to be described. A
continuously running motor 49 provides a reduction-gear output on a
vertical shaft 50 for developing an eccentric motion, from which torch
oscillation is picked off via a rod link 51. As shown, a boss 52 with a
radial groove or slot 53 is mounted to shaft 50, and externally accessible
means 54 enables radial-positioning adjustment of a crank-pin connection
(in groove 53) to rod 51, thus determining selection of the amplitude of
torch oscillation. Boss 52 is also shown with a cam formation 55 operative
upon the probe arm of a limit switch 56, once per revolution of shaft 50,
and for substantially one half of such revolution, for a valve-operating
and synchronizing purpose to be explained.
Another important feature of the invention is that in the indicated
torch-oscillating action, the metal powder to be applied to the workpiece
shall be applied intermittently and in synchronism with the desired
oscillatory motion. I have been able to achieve highly satisfactory
coatings, of smooth and uniformly continuous nature, using a cycle wherein
powder flow is admitted to the gas flow in torch T, once (and for
approximately a half cycle of oscillation) for every two cycles of
oscillation. More particularly, the torch T (see FIG. 3) may include a
valve 57 to control flow in an internal passage between a metal-powder
supply 58 and the interior of torch body 45. The valve 57 is shown to be
solenoid-operated at 59, being normally closed by spring means acting upon
a rod to squeeze and close an elastomeric valve section of the powder
passage. The described cycle of operating valve 57 is seen in FIG. 2 to
rely upon a divide-by-2 counter 60 connected to bi-stable flip-flop means
61 for controlling excitation of solenoid 59; and the curves of FIG. 3
show the sychronized relation between torch oscillation (curve a), the
substantially half-cycle nature of closure of the cam-operated switch 56
(curve b), and the divide-by-2 function of means 60-61 whereby solenoid 59
opens valve 57 only once for every two oscillatory cycles of torch T
(curve c). Legends applied at row d of FIG. 3 identify the metal-spraying
and purely fusing functions which result for the described operation of
valve 57.
FIG. 2 provides additional detail for an understanding of coordinated
automatic operation of my machine, and for simplification all electrical
return lines have been shown as grounded. Controls at the console 14
include a power shut-off button 62 with normally closed contacts, and
therefore circuit connection to a source (indicated by legend) will
immediately illuminate (a) a lamp 63, signifying "power on" to the
machine, and (b) a lamp 64, signifying "cycle-off", meaning that no cycle
or other automatic function of the machine is yet in progress. A push
button 65 is pressed to close its normally open contacts to supply
momentary excitation to a "latch-in" winding 66 having normally open
contacts 67 which are thus closed to latch (e.g., magnetically retain)
power to an automatic cycle-control system; normally closed contacts 68 to
lamp 64 are also operated by winding 66. Thus connected (upon closure of
contacts 67 and opening of contacts 68), a "cycle-on" lamp 69 illuminates,
the "cycle-off" lamp 64 extinguishes, and several parallel circuits are
also simultaneously established, namely:
1. Solenoid actuation of valve means 70 to open position, governing
admission of acetylene-gas supply to the torch inlet 46;
2. Solenoid actuation of valve means 71 to open position, governing
admission of oxygen-gas supply to the torch inlet 46';
3. Start of the motor 49, thus initiating the torch-oscillation action
already described;
4. Start of a preheat-cycle timer 76, to time out its period, predetermined
by adjustment at 76', it being noted that timer 76 is provided with
normally closed contacts 77 through which timer 76 is run, and with two
sets of normally open contacts 77'-77" both of which close upon completion
of the preheat-cycle timed interval;
5. Excitation of an indicator lamp 78, signifying that the preheat cycle is
in progress;
6. Start of a timer 73 via its normally closed contacts 74 to govern a
period of sparking from the ignition electrode 48 to nozzle 47; and
7. Excitation of an igniter transformer 75 having its secondary connected
to the lead to electrode 48. A short period, in the order of 10 seconds,
is more than ample for ignition time at 73, the same being disconnected at
74, upon lapse of the ignition-time interval.
During the preheat cycle, torch T courses the starting end of the desired
coating path, but no feed advance is started, and no metal powder is
sprayed. Then, when the predetermined preheat-cycle interval has been
timed out, the normally closed contacts 77 open, to extinguish the
preheat-cycle indicator lamp 78, and to allow the ignition circuitry to
reset. At the same time, normally open contacts 77' close to complete a
circuit to selector-switch means 72, for initiation of one or more of the
various feed drives, as appropriate for the particular working situation,
all as preset in selector-switch means 72 and other circuitry to be
described. Still further at the same time, contacts 77' close to complete
a circuit to limit switch 56 and thus to the means for initiating and
controlling the program of powder flow into the torch body 45.
It has been generally indicated that feed drives should be selected and set
for the requirements of a particular job. There are five drive motors
23-28-34-37-39, and in FIG. 2 these motors and their respective drive
controls are collectively designated by labeled boxes having primed
notation for the same identifying numerals. Each of these drives, for
example the X-drive 34', is operated via a series-connected limit switch
(79) to one of the selectable outlet terminals of selector-switch means
72, such limit switch having normally closed contacts connected to its
drive means and being mounted to monitor achievement of the preselected
end of the particular drive, the end of the particular drive being
additionally signalled by closure of normally open contacts of the same
limit switch. Thus, for the X-axis situation, limit switch 79 may be
carried by the X-axis alide 32, for ultimate coaction with an abutment 80,
adjustably clamped to ways 31, for terminating the X-drive when the
normally closed contacts of limit switch 79 are thereby opened; in like
manner, another limit switch 81 carried by the Y-axis slide may coact with
an end abutment 82 that has been adjustably clamped to the Y-axis ways 26,
and the remaining drives are correspondingly served by the normally closed
contacts of further limit switches 83-84-85.
Aside from the described normally closed limit-switch contact relationship
to each of the inputs to drives 34'-28'-23'-37'-39', the normally open
contacts of these limit switches are connected in parallel to complete a
circuit to a "latch-out" winding 87 associated with contacts 70, thereby
resetting the latter to their normally open condition and shutting down
all machine operations, including any and all feed drives, torch
oscillation, powder-flow, and torch-gas supplies. At this point, the
coating will have been applied as a continuous and complete swath, and the
workpiece may be removed from holder 12 for replacement with the next
workpiece and for an exact repeat of the described operations;
alternatively, and for the holder 12 accommodating two opposed harrow
point workpieces W, with all surfaces to be coated in the same radial
plane about the axis of .theta. rotation, the .theta.-drive may be
actuated to index the workpieces W for presentation of the next coating
path to working position, e.g., parallel to the X-axis ways 31.
In FIG. 2, semi-automatic means are schematically shown for such indexing
of the indicated workpieces W, for the simplified case in which for each
harrow point, the cutting-edge surfaces to be coated are equally inclined
on opposite ends of a plane of symmetry through the mounting means at
holder 12. The termination of each indexing step, for the four surfaces
(two on each harrow point) to be coated, is marked by the setting of
successive limit switches (L.S.-1, 2, 3, 4) at adjustably fixed positions
adjacent turntable 36 and about the axis of .theta.-rotation, said limit
switches being poised for successive actuation by a lug (not shown) on
turntable 36 and said limit switches having normally closed contacts which
open to terminate the particular increment of indexing (.theta.) rotation
which is selected by the currently stepped condition of step-switch means
89. The .theta.-Drive 37" thus affected is preferably separate from the
means 37' but is operative upon the same .theta.-Drive motor, so as to
avoid interference between a .theta.-Drive for indexing and a
.theta.-Drive for a working feed. Indexing is started by depressing a push
button 90 to pick up a latch-in winding 91, thus closing its normally open
contacts, to supply power to the .theta.-Drive 37" via the particular
normally closed limit-switch circuit that is determined by the currently
set condition of switch 89; indexing is completed when said particular
limit-switch circuit is opened, thus closing its normally open contacts to
complete a circuit to a latch-out winding 92 for returning contacts 91' to
their normally open condition, while at the same time supplying a
step-advancing impulse to the indexing step switch 89, at connection 93.
Also at the same time, excitation of latch-out winding 92 operates
associated normally closed contacts 92' to open condition, thereby
extinguishing a lamp 94 and indicating that indexing has been completed.
The various drive boxes 34'-28'-23'-37'-37"-39' of FIG. 2 have been
indicated schematically and are to be understood to suggest use of one or
more of a variety of motor-drive controls. By the same token, adjustment
knobs a at each of these boxes will be understood to suggest manual or
other setting of the control function (for example, speed) for the
particular motor drive involved. Thus, whichever one or more of the feed
drives that has been selected by means 72 to be operative for a given
working operation may involve steady, continuous and relatively slow feed
during the course of the relatively rapid oscillatory trasverse of the
work path by reason of eccentric-throw pickoff by rod 51. Alternatively,
upon selective closure of a switch 95, an intermittent feed-drive control
96 may be caused to advance the applicable one or more of the feed drives,
once per eccentric cycle. To this end, closure of switch 95 enables means
96 to respond to the cam-operated output of switch 56 (curve b of FIG. 3),
so that the particular feed drive is only advanced at such intermittent
times, thus allowing at least one non-spraying torch impingement upon a
given area of the working path for each metal-spraying pass of precisely
the same area. Upon proper phase adjustment of output signal from (with
respect to input signal to) the control means 96, such adjustment being
suggested by manual means 97, the first torch pass over a specific
traverse line may be a local surface preheating (non-spraying) pass, so
that the next-ensuing pass may be metal-spraying. Thereafter, the
cam-derived feed-advancing signal will be operative to advance the
particular feed to the extent of substantially half the width of a spray
bead while another full cycle of oscillation proceeds without metal
spraying, thus avoiding extended time for fusing the most-recently
deposited metal with respect to metal deposited on preceding passes.
The foregoing discussion with respect to metal beads and spraying vs.
fusing oscillatory traverses of the work path will be better understood
from a consideration of FIGS. 4 and 5, both of which are simplified
diagrams, for illustrative explanation only. The diagram of FIG. 4 depicts
the application of successively sprayed beads m-n-o-p-q-r to the desired
upper surface region of the workpiece W, in the course of torch feed in
the direction indicated by legend and a heavy arrow, and with torch
discharge directed as also indicated by an arrow. Successive beads
longitudinally overlap each other to the extent of approximately 25
percent of the width of individual beads, but without an adequate fusing
interval between successive spraying passes (e.g., in certain instances a
one-half cycle of oscillation between successive spray passes is not
sufficient), the beads do not fuse to each other; poor bonding results, as
between each bead and adjacent substrate, and as between adjacent beads.
On the other hand, with an extended fusing interval between spray passes,
as suggested at c and d in FIG. 3, the fusing heat between bead sprays is
effective to "puddle" each bead to those which preceded it, thus producing
the smooth and continuous coating suggested at 98 in FIG. 5, with the most
recently applied bead r' being due for "puddled" assimulation into the
single coating layer 98 in the course of the three fusing (non-spraying)
passes to occur before the next metal-spraying pass of the work path
occurs.
The overlay coat 98 may range in thickness from about 0.005 to 0.02 inch,
and each bead width may range from 0.05 to 0.3 inch, for a
nozzle-discharge distance of about 0.75 inch.
Metal powder suitable for the described intermittently sprayed application
to a metal substrate generally comprises self-fluxing nickel-base,
cobalt-base, iron-base and copper-base alloys. The self-fluxing properties
are due to the presence of silicon and boron in the coating-metal powder.
As regards the self-fluxing nickel-base, cobalt-base and iron-base alloys,
the alloys generally contain by weight about 0.05 to 6 percent Si, about
0.5 to 5 percent B and up to about 3 percent C, the balance being
essentially either nickel, or cobalt, or iron together with alloying
elements, such as Cr, W and Mo.
A typical nickel-base alloy may contain by weight about 0.5 to 3 percent
Si, about 1 to 5 percent B, 0 to about 15 percent Mo., 0 to 15 percent W,
and the balance essentially nickel, the total Cr + Mo + W content ranging
up to about 30 percent.
A typical cobalt-base alloy may range in composition by weight from about
0.5 to 3.5 percent Si, about 1 to 3 percent B, 0 to about 3 percent C,
about 5 to 30 percent Cr, 0 to about 15 percent Mo, 0 to about 15 percent
W, and the balance essentially cobalt, the total Cr + Mo + W content
ranging up to about 30 percent.
The iron-base alloy may range in composition by weight from about 0.5 to 3
percent Si, about 1 to 3 percent B, 0 to about 3 percent C, about 5 to 25
percent Cr, 0 to about 15 percent Mo, 0 to about 15 percent W, and the
balance essentially iron, the total Cr + Mo + W content ranging up to
about 30 percent.
The indicated coating alloys are formulated to provide melting points
ranging up to about 2500.degree. F. (1371.degree. C.), the melting points
ranging from about 1800.degree. F. (983.degree. C.) to 2250.degree. F.
(1233.degree. C.). The melting point is controlled by the amount of
silicon and boron in the alloy. The coating is applied by flame-spraying
an alloy powder of the composition (e.g., atomized powder). The
alloy-powder particle can be of mesh size ranging from less than 125 mesh
(about 125 microns) to about 400 mesh size (about 40 microns). Mesh size
referred to herein is based on U.S. Standard.
It will be seen that I have described means and methods which meet all
stated objects. My invention brings an individual art form to a
predictable level of high performance and product quality, to the extent
that far less operator skill is required, wastage of materials is
substantially reduced, and production capabilities greatly enhanced. And
these results are obtained for a tremendous variety of work requirements.
To illustrate efficacy of the invention, I provide below three specific
examples of automated coating, using the machine which I have described.
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EXAMPLE I
Workpiece: Harrow Points, being catalog Part
No. "479008R2-12" of International
Harvester Company; top surface at
right and left cutting edges to be
coated, each with 0.75-inch wide
path, of 9-inch length to path
intersect at pointed end. Mounted
in duplicate, as shown in FIG. 1A,
and indexable in .theta. increments, for
successive coatings of the four
edges, as described above.
Oscillating Traverse Span:
1.00 inch
Traverse Cycle:
1 per second.
Metal-spray duty cycle:
20 to 25 percent of two-cycle
period of oscillation.
Feed: Continuous, along X-axis.
Feed rate: 3-4 inches per minute.
Metal-Powder, at 58:
"LUBROTEC 19985"*; about 1.5 to
2 ounces consumed per treated
edge; coated-layer (98) thickness
of about 0.025 inch.
REMARKS: Longitudinal cut through coated path, the cut
being taken longitudinally along the path (in the sense
of the sections of FIGS. 4 and 5), showed uniform layer
as at 98, with no residuum of individual beads; puddling
mix of adjacent beads was such as to eliminate outer-
surface ripple to substantially less than 10 percent of
stated coating thickness.
EXAMPLE II
Workpiece: Harrow Disc, 20-inch diameter
and dished, being catalog Part
No. "JD 35 #B 3134" of Deere & Co.,
Moline, Illinois; convex surface
to be coated with 0.75-inch wide
circumferentially continuous
annular path. Mounted at center,
to pedestal on turntable 36, as
shown in FIG. 1B, with cradle
tilted about 30 degrees to permit
torch oscillating traverse to be
at substantially uniform spacing
from instantaneously treated region
of convex surface.
Oscillating Traverse Span:
1.00 inch
Traverse Cycle:
1 per second
Metal-Spray duty cycle:
20 to 25 percent of two-cycle
period of oscillation.
Feed: Continuous .theta. rotation
Feed rate: About 18 to 20 min/rev.
*Trademark of Eutectic Corporation, New York, New York, for its machinabl
coating (overlay) powder.
Metal powder, at 58:
"LUBROTEC 19985"; about 15 ounces
consumed per treated edge; coated-
thickness layer (98) of about
0.025 inch.
REMARKS: Smooth and continuous,
as in Example I.
EXAMPLE III
Workpiece: Helical Earth-Auger, 18-inch
diameter by 13.5-inch advance/turn,
being catalog Part No. "JD HDG 530"
of Deere & Co.; periphery of lower
surface of blade to be coated with
1.5-inch wide continous path.
Auger stem held inverted by lathe
chuck 36' secured to turntable 36,
with stem axis vertical, for
.theta. rotation about vertical axis, as
shown in FIG. 1C.
Oscillating Traverse Span:
1.75 inch
Traverse Cycle:
0.6 per second
Metal-spray duty cycle:
20 to 25 percent of two-cycle
period of oscillation.
Feed: Continuous .theta. rotation, with
synchronized Z-axis drive,
mechanically geared synchronizing
of these feeds being as suggested
schematically at 99 in FIG. 2.
Feed rate: 25 to 28 minutes for the single-turn
helical advance of the workpiece.
Metal Powder, at 58:
"LUBROTEC 19985"; about 30 ounces
consumed per treated edge; coated-
thickness layer (98) of about 0.025
to 0.030 inch.
REMARKS: Smooth and continuous, as
in Examples I and II.
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While the invention has been described in detail for the presently
preferred form, it will be understood that modifications may be made
without departing from the invention. For example, the torch T which
happens to be of the internal-powder-feed variety may and in certain cases
preferably is replaced by an external-powder-feed torch, or a
two-powder-feed torch, as of the kind described in greater detail in my
copending patent application Ser. No. 728,202, filed Sept. 30, 1976.
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