Note: Descriptions are shown in the official language in which they were submitted.
CA 02485302 2004-10-19
DUAL-PROCESS POWER CABLE WITH
INTERCHANGEABLE TIG WELDING
TORCH AND SMAW ELECTRODE HOLDER
BACKGROUND OF THE INVENTION
This invention generally relates to cables for supplying welding
power from a power supply to a welding site. In particular, the invention
relates
to cables for supplying welding power to electrodes used in gas tungsten arc
welding (GTAW) (also known as tungsten inert gas (TIG) welding) and shielded
metal arc welding (SMAW) (also called "'Stick" welding).
Power supplies such as welding power supplies are used to
provide high-amperage current. Typically, in a welding power supply, a pair of
output terminals is provided. A welding cable connected to the welding torch
(or
stinger, drive assembly or welding circuit) is inserted into one of the two
output
terminals. The other output terminal receives a welding cable that is
connected
to the workpiece being welded. In some systems, the connectors are twist-lock
type connectors (also called "international connectors"), the power supply has
a
female connector, and the welding cable has a mating male connector. In other
systems, the cable has a female connector and the power supply a male
connector.
In a conventions! TIG welding process, a concentrated high-
temperature arc is drawn between a non-consumable tungsten electrode and a
workpiece. The workpiece is connected to the output of a welding power source
via a work clamp. The tungsten electrode is nested in a torch that comprises a
shielding gas source, such as a cup, to direct a shielding gas, such as argon,
helium, a mixture thereof, or other inert or non-inert gases, to a welding
site on
the workpiece. The torch receives a flow of shielding gas from a gas cylinder.
In
accordance with known techniques, the welder may strike an arc by touching or
scratching the electrode against the workpiece to close a circuit between the
electrode and the work clamp. As the electrode is drawn away from the
workpiece, an arc is initiated. Alternatively, the arc is initiated using a
high-
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frequency electrical impulse provided by the welding power supply, which
jumps to the workpiece. The welder then feeds a bare welding rod to the
welding site. More precisely, the tip of the welding rod is inserted into the
gap
between the electrode tip and the welding site. The arc that crosses the gap
from the electrode tip to the workpiece causes the tip of the welding rod and
the
underlying workpiece material at the welding site to melt, thereby creating a
molten puddle. During a single welding pass, the arc and the welding rod must
be moved in unison in order to. effect a weld bead. The displaced arc leaves
the
molten puddle in its wake. The portion of the molten puddle furthest from the
90 arc hardens continuously to leave a weld bead joining two pieces of metal.
When welding with the TIG process, the majority of heat goes
into the arc, however a significant amount is retained in the torch.
Typically,
means are provided for removing the wasted heat. Torches for GTAW welding
may be either water- or air cooled. High-production or high-amperage torches
are. usually water-cooled, while lighter-duty torches for low-amperage
applications may be air-cooled.
The SMAW process d'rffers from the GTAW process in several
fundamental respects. First and foremost, a consumable electrode is used.
Typically the electrode consists of a core of mild steel wire or other known
material and a sheath surrounding the core and comprising a special coating
that assists in creating the arc and at the same time produces a shielding
atmosphere that protects the molten steel as it transfers across the arc. The
consumable electrode is typically held between a pair of jaws made of
electrically conductive material and electrically coupled to the power cable.
When no more of the electrode held by the jaws can be consumed, it must be
replaced by a new consumable electrode. Another difference is that the SMAW
electrode holder does not need to be cooled. Also, shielding gas need not be
soun;ed from the power supply unit in the SMAW process.
The greatest advantage of the GTAW process is that it will weld
more kinds of metals and metal alloys than any other arc welding process.
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GTAW can also weld dissimilar metals to one another, such as copper to brass
and stainless steel to mild steel. The concentrated nature of the GTAW arc
permits pinpoint control of heat input to the workpiece, resulting in a nan-ow
heat-affected zone. There is no requirement for flux with this process.
Therefore, there is no slag to obscure the welder's vision of the molten weld
pool. Also, in the GTAW process there is no transfer of metal across the arc.
Thus there are no molten globules of spatter (as in SMAW) to contend with.
The process itself does not produce smoke or injurious fumes.
The main disadvantage of the GTAW process is the iow filler
metal deposition rate. Another disadvantage is that the hand-eye coordination
necessary to accomplish the weld is difficult to team, and requires a great
deaf
of practice to become proficient. In contrast, in SMAW the electrode melts and
becomes filler metal Also, the arc rays produced by the GTAW process tend to
be brighter than those produced by SMAW. When welding in confined areas,
concentrations of shielding gas may build up and displace oxygen.
In practice, a TIG welding torch is connected to a main unit that
supplies power, shielding gas and coolant (if required) by means of a cable
that
comprises an electrical conductor, a channel for shielding gas, and in the
case
of a water-cooled torch, outbound and return channels for recirculating
cooling
water. In the case of an air-cooled torch, the water channels can be
eliminated
and the shielding gas can also be used for cooling the torch. In the case of
Stick welding, the SMAW electrode holder is connected to the main unit via a
power cable. It is known to provide different cables that are dedicated for
use
with a TIG torch or with a SMAW electrode holder respectively.
It is also known to provide a dual-purpose cable that can be used
with either a TIG torch or a SMAW electrode holder, the torch and electrode
holder being interchangeable. However, in this known combination torch setup,
the cable has a threaded male connection. The amount of time needed to
change the welding head becomes excessive because of this threaded
connection, which requires the installed head to be unscrewed and the new
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head to be screwed, each operation requiring multiple turns. The known
arrangement also has the disadvantage that it allows an electrically hot
connector to be exposed during changing of the welding head, potentially
creating a safety hazard.
There is a need for a power cable with interchangeable TIG torch
and SMAW electrode holder that overcomes the aforementioned problems.
BRIEF DESCRIPTION OF THE INVENTION
The invention is directed to a power cable with interchangeable
TIG torch and SMAW electrode holder in which the heads can be interchanged
quickly without tools and without the hazard of an exposed electrically hot
male
connector at the end of the cable. This is accomplished by providing a female
receptacle at the head end of the power cable. The TIG torch and the SMAW
electrode holder are each provided with the same type of male connector for
coupling with the female receptacle on the head end of the power cable. The
male connectors and the female receptacle may be of the twist-lock or similar
variety. The provision of a single power cable with interchangeable heads for
use in TIG welding or SMAW reduces confusion at the worksite, reduces the
cost of equipment, and increases flexibility in the welding operations.
One aspect of the invention is a kit comprising: a power cable
comprising a female receptacle at a head end; a TIG welding torch comprising
a first plug that can be coupled in the female receptacle of the power cable;
and
a SMAW electrode holder comprising a second plug that can be coupled in the
female receptacle of the power cable.
Another aspect of the invention is a kit comprising: a power cable
comprising a female receptacle at a head end; a T1G welding torch comprising
a first male connector that can be coupled in the female receptacle of the
power cable; and a SMAW electrode holder comprising a second male
connector that can be coupled in the female receptacle of the power cable. The
female receptacle is not threadably engaged with the portion of the first or
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second male connector inserted therein.
A further aspect of the invention is an assembly comprising: a
power cable comprising an electrical conductor running the length of the power
cable, a first electrical connector at a head end of the power cable and a
second electrical connector at the other end of the power cable, and further
comprising a channel running along the length of the power cable, the channel
being at least partially occupied by a gas; and a SMAW electrode holder
comprising a third elect~cal connector coupled to the first electrical
connector of
the power cable.
Yet another aspect of the invention is a method for changing the
welding mode of a welding system: comprising the following steps: uncoupling
a first welding head from a head end of a power cable by a relative movement
different than unscrewing; and coupling a second welding head from the head
end of the power cable by a relative movement different than screwing, wherein
one of the first and second welding heads is a TIG welding torch and the other
of the first and second welding heads is a SMAW electrode holder.
Other aspects of the invention are disclosed and claimed below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a drawing showing a partially sectioned view of a known
TIG welding torch.
FIG. 2 is a drawing showing an exploded view of a TIG
torch/power cable assembly in accordance with one embodiment of the present
invention.
FIG. 3 is a drawing showing the TIG torch/power cable assembly
of FIG. 2.
FIG. 4 is a drawing showing a partially sectioned view of the
skeleton of the torch body depicted in FIG. 2.
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FIG. 5 is a drawing showing a side view of the torch body
depicted in FIG. 2.
FIG. 6 is a drawing showing a side view of a nipple with female
receptacle incorporated in the power cable depicted in FIG. 2.
FIG. 7 is a drawing showing a side view of the power cable
handle shown on a smaller scale in FIG. 2.
FIG. 8 is a drawing showing a side view of a SMAW electrode
holder that can be interchanged with the TIG torch depicted in F1G. 3.
FIGS. 9 and 10 are drawings showing side and end views
respectively of a handle for the SMAW electrode holder shown in FIG. 8.
Reference will now be made to the drawings in which similar
elements in different drawings bear the same reference numerals.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with one embodiment of the invention, a welding
system is provided wherein a TIG welding torch and a SMAW electrode holder
can be interchangeably connected to a welding power supply unit via the same
power cable. The single cable is capable of carrying cun-ent for either TIG or
Stick welding processes. This single lead also carries shielding gas to the
work
site for TIG welding. This lead incorporates a female connection at the work
site, allowing the operator to interchange a Stick electrode holder and a TIG
torch. The Stick electrode holder and TIG torch each incorporate a male
connector that mates with the female connector in the power cable. These
heads can be easily interchanged without the use of tools.
A known air-cooled TIG welding torch is depicted in FIG. 1. The
torch comprises a torch head section and torch handle section. The head
section comprises an internally threaded barrel 2 formed of copper or other
highly electricailyconductive metal or alloy for retaining a tungsten
electrode 4.
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The electrode 4 is coaxially supported with respect to barrel 2 by means of a
collet 6 formed by a tubular inner sleeve having longitudinal slots that
define
spring fingers that clamp onto the electrode 4. The collet 6 is in turn
inserted
within a collet body 8. The externally threaded rear end of collet body 8 is
received within the lower forward end of barrel 2. The collet body 8 further
comprises a nose projection 10 having multiple apertures 12 (only one of which
is visible in FIG. 1 ) for emitting shielding gas introduced into the space
between
collet 6 and collet body 8.
The forward end of collet body 8 adjacent nose 10 is externally
threaded to engage an internally threaded nozzle 14 formed of a temperature-
resistant ceramic material. The shielding gas emanates from apertures 12 in
the nose 10 of the collet body 8 and flows through the nozzle 14 to envelop
the
welding zone. The rearward end of nozzle 14 is tapered to nest within a front
insulating collar 16 that is snapped onto the forward end of a cylindrical
insulating jacket 18 that surrounds the barrel 2. The jacket 18 is molded of
an
elastomeric material. A back insulating collar 20 snaps onto the rearward end
of
the jacket 18. A tubular stem 22 of a back cap 24, in which the rear portion
of
electrode 4 is disposed, extends through the back insulating collar 20 and
threadably engages the rear end of the barrel 2. An O-ring seal 26 is disposed
between the back insulating collar 20 and the back cap 24.
The barrel 2 of the torch head section is joined to the handle
section by means of a tube 28 made of a highly electrically conductive metal
or
alloy. The end of the tube 28 is connected to barrel 2 and extends laterally
therefrom at an oblique angle relative thereto. A cylindrical connector 30
made
of an electrically conductive material is connected onto the rearward end of
tube 28 for connecting the torch to a source of welding current as welt as to
a
pressurized source of shielding gas. The connector 30 in its forward end has
an
internal bore 32 equal in diameter to the internal diameter of tube 28. The
rear
portion of connector 30 has a bore 34 of larger diameter, which is internally
threaded to accommodate a conventional externally threaded coupler 36 on the
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CA 02485302 2004-10-19
head end of a power cable 38. Shielding gas flows in series through a channel
inside the cable 38; through the bores of the coupler 36, the connector 30 and
the tube 28; into the annular space between the barrel 2 and the collet 6;
through the space inside the collet body 8; and out the apertures 12 in the
nose
10 of the collet body 8.
A cylindrical body 40, made of an elastomeric insulating material
such as silicone rubber, is molded over and around the tube 28. In fabricating
the torch body, the barrel 2 and tube 28 are placed in a mold into which a
silicone rubber molding compound is injected to form the molded body 40,
which body also surrounds the barrel 2 to define jacket 18. The mold is
designed to form suitable flanges at the opposite ends of the jacket for
mounting the front and back insulating collars. The mold is also designed to
form a shoulder 42 and a plurality of spaced annular ribs 44 to the rear of
the
shoulder 42. The ribbed section of the molded body is disposed within a
tubular
handle 46 made of electrically insulative material. The fonnrard end of handle
46
abuts shoulder 42. The electrically insulative handle 46 surrounds the
electrically hot connector 30.
In accordance with one embodiment of the present invention, a
TIG welding torch is provided having a torch head section similar to that
shown
in FIG. 1, but a different torch handle section. More specifically, the torch
handle section has a male connector that connects the TIG torch section to a
complementary (i.e., mating) female connector (i.e., receptacle) on the end of
the power cable. In this embodiment, the male connectors and the female
receptacle may be of the twist-lock or similar variety. In addition, a SMAW
electrode holder is provided that is interchangeable with the TIG welding
torch.
In other words, the same power cable can be used with different heads, one
having a TIG welding torch and the other having a SMAW electrode holder.
The power cable in accordance with the aforementioned
embodiment will be described hereinafter with reference to FIGS. 2, 3, 6 and
7,
while the TIG welding torch in accordance with the aforementioned
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embodiment will be described with reference to FIGS. 2-5. The SMAW
electrode holder in accordance with the aforementioned embodiment (which
can be coupled to the power cable in place of the TIG welding torch in the
assembly depicted in FIG. 3) will be described hereinafter with reference to
FIGS.8-10.
Referring to FIG. 2, the components of the TIG torch headlpower
cable assembly comprise a TIG welding torch 100 (only partially depicted), a
TIG welding torch handle 102, a power cable 104 (only the ends of which are
shown), and a power cable handle 106. The same components are shown in
an assembled state in FIG. 3.
The TIG welding torch comprises an electrically conductive
skeleton 108 (shown in FIG. 4), which is partially overmolded with
electrically
insulative material, as shown in FIG. 5. Referring to FIG. 4, the electrically
conductive skeleton 108 comprises a coupling 50 and a male connector 52
(which may be formed as one piece, as seen in FIG. 4, or as two pieces
connected together). The skeleton further comprises a tube 28 having one end
brazed to the coupling 50 and the other end connected to a barrel 2 (also part
of the skeleton). The skeleton components may be made of copper, brass or
other suitable electrically conductive material suitable for carrying welding
current. The coupling 52 has a central circular cylindrical bore 53 for
passage of
shielding gas. The bore 53 is coaxial with the bore of tube 28. The barrel 2
and
the tube 28 are overmolded with electrically insulative material, thereby
forming
cylindrical body 40 (with shoulder 42 and ribs 44) surrounding the tube and a
jacket 18 surrounding the barrel, as seen in FIG. 5.
The TIG welding torch is shown in FIGS. 2 and 3 without the
nozzle, back cap, collet, collet body, and tungsten electrode, which may be
similar to those components as depicted in FIG. 1. FIGS. 2 and 3 each show
the front collar 16 and the back collar 20, both of which are made of
electrically
insulative material.
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As seen in FIG. 2, the power cable has a female receptacle 54 at
the head end and a male plug, comprising a nut 58 and a nipple 58', at the end
that connects to the welding power supply unit. The latter end will typically
be
male, but could be female, and could be threaded, international style, a lug,
or
permanently affixed to the welding power supply. The cable comprises a hose
56 made of flexible, electrically insulative material and having a circular
channel
for the passage of shielding gas. One end of the hose 56 is crimped onto a
nipple 64 (shown in dashed fines in FIG. 2) by a brass ferrule 60. The nipple
64
and the female receptacle 54 are formed as one piece, as best seen in FIG. 6.
The other end of the hose 56 is crimped onto a nipple 58' by a ferrule 61. One
end of a cable 62 is crimped onto nipple 58'. The cable 62 carries welding
current from the power supply to the female receptacle 54 and has a
cylindrical
gas passage through the center.
The components depicted in FIG. 2 are assembled as follows.
First, the power cable handle 106 is slid over the head end of the power cable
104. As seen in FIG. 7, the power cable handle 106 has a bore 94 with an
internally threaded section 96. The threaded section 96 engages the externally
threaded female receptacle 54, enabling the handle 106 to be tightened onto
the head end of the power cable 104. Next, the torch handle 102 is slid over
the
power cable 106. Then the male connector 52 of the TIG welding torch 100
(see FIG. 5) is inserted into an opening 78 formed in the female receptacle 54
(see FIG. 6). The opening in the female receptacle has a shape that matches
the end profile of the male connector, which is a circular tube shape with a
projection or key 51 (see FIG. 5) on its outer peripheral surface. The male
connector 52 can only be inserted into the female receptacle when projection
51 is aligned with a corresponding recess that forms part of the opening in
the
female receptacle. The male connector 52 is inserted until projection 51 is
aligned with the entrance to a groove 76 (see FIG. 6) defined in part by a
shoulder having a ramped wall or cam 77 in the shape of a helical section that
transitions to a landing at a stopping point. By turning the torch relative to
the
power cable, the projection 52 enters the groove, rides along the helical
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CA 02485302 2004-10-19
77 (thereby tightening the male connector inside the female receptacle), and
is
stopped at a fully tightened position. The entire rotation of the torch
relative to
the power cable during coupling may be on the order of one-half tum.
After the male connector of the welding torch 100 is tightly
coupled to the female receptacle at the head end of the power cable 104, the
torch handle 102 is slid toward the torch. More specifically, the torch handle
102
is slid over the ribbed portion of the molded cylindrical body 40. The ribbed
portion comprises a circular cylindrical section having a plurality of
external
annular ribs 44 projecting radially outward at regular spaced intervals along
a
longitudinal axis. Each rib 44 has an outer diameter greater than the internal
diameter of section 98 of the internal bore of the torch handle 102 (see FIG.
2).
However, since the molded body 40 and its ribs 44 are made of resilient
material, the ribs 44 will compress as the torch handle 102 is pushed onto the
ribbed cylindrical section. When the end of the torch handle 102 abuts the
shoulder 42, as seen in FIG. 3, the torch handle cannot be pushed further. In
the state shown in FIG. 3, the friction between the compressed ribs 44 and the
internal surface 98 (see FIG. 2) holds the torch handle 102 securely in place.
As shown in FIG. 6, the female receptacle 54 is integrally formed
with a nipple 64, which is inserted inside the hose of the power cable. A
section
of the nipple 64 is provided with a series of conical ridges 70 that slide
easily
into the hose. and resist being pulled out of the hose. As previously
described,
the hose has a circular channel for the passage of shielding gas from the
shielding gas supply through the power cable and toward the welding torch.
Although not shown in the drawings, the end of the nipple 64 is D-shaped after
being crimped onto the weld cable. In other words, the nipple 64 has a flat
side
66 that provides relief for the shielding gas to flow into a gas port 68. The
piece
shown in FIG. 6 also has a circular central channel 72 for the shielding gas.
One end of the channel 72 communicates with the space adjacent the flat side
66 via the gas port 68. The other end of the channel 72 (located inside the
female receptacle 54) will communicate with one side of an O-ring 79 (see FIG.
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6), which is seated along the periphery of a disk-shaped space 74 in the
female
receptacle 54. The space 74 communicates with one end of channel 72. The
male connecter 52 is inserted into female receptacle 54 and rotated. When the
male connector and female receptacle are tightly coupled, the O-ring 79 is
compressed between the end of the male connector and the female receptacle
54 to form a hermetic seal that prevents shielding gas from leaking through
the
interstice between the male and female connectors. Instead, the shielding will
flow under pressure from the channel 72 (see FIG. 6) into the bore 53 of the
coupling 50, and then down the bore of the tube 28 (see FIG. 4).
When the operator wishes to interchange a SMAW electrode
holder for the TIG welding torch 100 shown in FIGS. 2 and 3, the torch handle
102 is slid away from the torch and the torch is unscrewed from the power
cable. Both the torch 100 and torch handle 102 are then removed and replaced
by a SMAW electrode holder (shown in FIG. 8) and a Stick handle (shown in
FIGS. 9 and 10).
Referring to F1G. 8, the SMAW electrode holder 110 comprises a
body 80 made of electrically conductive material (e.g., brass). One end of the
body 80 forms a jaw 84. Another jaw 82 (made, e.g., of the same electrically
conductive material) is connected to a lever 86, the jaw 82 and lever 8fi
being
operatively coupled to the body 80 by a hinge point (not shown in FIG. 8) and
a
coil spring 88. When the lever 86 is depressed, the jaws 82 and 84 open and a
consumable electrode (not shown) can be inserted between the jaws. When
the lever is released, the coil spring 88 causes the jaws to hold the
consumable
electrode securely. The jaws are covered by respective covers 90 and 92 made
of an electrically insulative material, such as thermoset plastic.
A male connector 52' is connected to the other end of the body
80. The end of the male connector 52' is similar in external shape to the end
of
the male connector in the TIG welding torch, but differs in that it lacks a
passageway or channel for shielding gas, i.e., the male connector 52' can be
solid, not hollow. The male connector 52' is inserted into the above-described
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female receptacle and locked in place when the projection or key 51 is rotated
into the groove inside the female receptacle and latched behind a shoulder
that
forms that groove. In the particular example disclosed herein, the female
receptacle 54 (see FIG. 6) is an International-style receptacle.
The electrode holder handle 112 (see FIG. 9) is a generally
circular cylindrical structure that slides over the body 80 (see FIG. 8) of
the
SMAW electrode holder. The bore 114 of the handle 112 intersects the annular
plateau 81 formed on the body 80. The handle 112 has a slot 118 (see FIG. 10)
that provides clearance for the lever 86 and the coil spring 88. The handle
112
is then secured by a set screw 83 whose head is backed into a circular hole 85
in the handle. The insertion of the screw head into hole 85 prevents the
handle
from sliding off.
The power cable (104 in FIG. 3) can carry current for either TIG
welding or SMAW. The female receptacle has a passageway for shielding gas.
When a TIG welding torch is connected to the female receptacle, the power
cable provides both welding current and shielding gas to the TIG welding
torch.
When a SMAW electrode holder is connected to the female receptacle, the
power cable provides only welding current, i.e., the passageways for shielding
gas are not used.
While the invention has been described with reference to
preferred embodiments, it will be understood by those skilled in the art that
various changes may be made and equivalents may be substituted for
members thereof without departing from the scope of the invention. In
addition,
many mod~cations may be made to adapt a particular situation to the
teachings of the invention without departing from the essential scope thereof.
Therefore it is intended that the invention not be limited to the particular
embodiment disclosed as the best mode contemplated for carrying out this
invention, but that the invention will include all embodiments falling within
the
scope of the appended claims.
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