A plasma arc welding torch is discussed. A first plasma gas is directed through the body of the welding torch and out of the body across the tip of a welding electrode disposed at the forward end of the body. A second plasma gas is disposed for flow through a longitudinal bore in the electrode. The second plasma gas enters one end of the electrode and exits the electrode at the tip thereof for co-acting with the electric welding arc to produce the desired weld. A shield gas is directed through the torch body and circulates around the head of the torch adjacent to the electrode tip

Mcgee, William F.

Rybicki, Daniel J.

Waldron, Douglas J.

English

NASA Technical Reports Server

I11111 1ll11 IIIII 11111 11111 11111 Il1 11111 11111 11111 ll11 IIIII 1111 
US005399831A 
United States Patent [191 1111 Patent Number: 5,399,831 
McGee et al. 1451 Date of Patent: Mar. 21, 1995 
1541 
1751 
1561 
TERNARY GAS PLASMA WELDING TORCH 
Inventors: William F. McCee, Decatur; Daniel 
J. Rybicki, Huntsville, both of Ala.; 
Douglas J. Waldron, Palmdale, Calif. 
The United States of America as 
represented by the Administrator, 
National Aeronautics and Space 
Administration, Washington, D.C. 
Assignee: 
Appl. No.: 172,961 
Filed: Dec. 27,1993 
Int. Cl.6 .............................................. B23K 10/00 
U.S. Cl. ............................ 219A21.45; 219/121.5; 
219/121.51: 219A21.48 
Field of Search ...................... 219/121.45, 121.48, 
219A21.5, 121.51, 121.52, 75 
References Cited 
U.S. PATENT DOCUMENTS 
4,964,568 10/1990 Rotolico et al. ................. 219/76.16 
4,990,739 2/1991 Zapatynsky .................... 219A21.47 
5,148,986 9/1992 Rusch ............................. 219/121.51 
5,194,715 3/1993 Severance, Jr. et al. ...... 219A21.48 
Primaly Examiner-Mark H. Paschal1 
Attorney, Agent, or Firm-Robert L. Broad, Jr.; Guy M. 
Miller; Alan J. Kennedy 
A plasma arc welding torch wherein a first plasma gas 
is directed through the body of the welding torch and 
out of the body across the tip of a welding electrode 
disposed at the forward end of the body. A second 
plasma gas is disposed for flow through a longitudinal 
bore in the electrode. The second plasm gas enters one 
end of the electrode and exits the electrode at the tip 
thereof for coacting with the electric welding arc to 
produce the desired weld. A shield gas is directed 
through the torch body for circulating around the head 
of the torch adjacent the electrode tip. 
1571 ABSTRACT 
3,628,079 12/1971 Dobbs et al. .......................... 219/75 4 Claims, 2 Drawing Sheets 
SECONDARY INERT 
PLASMA GAS 
PRIMARY INERT 
PLASMA GAS 
PRIMARY INERT 
PLASMAGAS -1 
INERT 
SHIELDING 
16 
TUBULAR 
ELECTRODE ( 36) PLASMA CONSTRICTING. 
ORFICE (47) 
PLASMA ARC PLUME 
https://ntrs.nasa.gov/search.jsp?R=19950019128 2020-06-17T23:49:25+00:00Z
U.S. Patent Mar. 21, 1995 Sheet 1 of 2 5,399,83 1 
34 
26 
FIG. 1. 
FIG. 2. L! 3 
FIG. 3. 
U.S. Patent Mar. 21, 1995 Sheet 2 of 2 
PLASMA GAS 
SECONDARY INERT 
PLASMA GAS 
PRIMARY INERT 
PLASMA GAS 
PRIMARY INERT 
5,399,831 
INERT 
SHIELDING GAS 
t 
5,39933 1 
1 
electrical current setting, thereby producing a more 
desirable Heat Affected Zone (HAZ) and greater ulti- TERNARY GAS PLASMA WELDING TORCH 
mate tensile strength values. 
The jet of secondary orifice gas channeled through 
5 the tubular electrode compliments the primary inert gas 
column channeled through the torch body to Provide a 
“Stiffer” arc less subject to becoming skewed and un- 
equal in dimensional shape. This characteristic will aid 
in alleviating weld “cutting” defects caused by an asym- 
metrical arc and subsequent asymmetrical heating Dat- 
ORIGIN OF THE INVENTION 
under contract NAS8-36200 awarded by the National 
Aeronautics and space Administration. The Govern- 
ment has certain rights in this invention. 
mS invention was made with 
FIELD OF THE INVENTION 
This invention relates generally to plasma arc weld- 
ing torches and more particularly to plasma arc welding 
torches having a hollow electrode including a tip 
through which an inert gas flows. The inert gas exits the 
electrode at the tip and coacts with an electric arc gen- l5 
erated at the tip to form an arc plume which is directed 
onto the workpiece. 
BACKGROUND OF THE INVENTION 
placing a welding torch adjacent a workpiece and di- 
recting an inert gas across the tip of an electrode pro- 
vided in the torch body and onto a workpiece. The 
interaction of the inert gas and hot electrode forms a 
substantially constricted arc between the tip of the elec- 25 
trode and the workpiece. 
In a typical plasma arc welding torch, the electrode is 
comprised of a refractory material and is mounted in the 
torch body in thermally and electrically insulated rela- 
tion therewith. The electrode is enclosed by the torch 30 
body and an inert gas is directed through channel or 
Plasma arc welding is generally accomplished by 20 
channels in the torch body and across The tip of the 
electrode and exits the body along with the electric arc, 
through an opening in the forward portion of the body. 
The inert gas acts upon the electric arc present be- 
tween the electrode and the workpiece to constrict its 
shape to that of a substantially narrow column. T h e  
inert gas also provides the necessary atmosphere which 
allows for electrical transfer of the arc across the gap 
formed between the electrode and the workpiece. In 
addition, this inert gas (defined herein as a primary 
orifice gas) provides some shielding effect to the molten 
weld zone as well as penetration control of the arc, 
depending on the volume of orifice gas flowing through 
the torch body. However, typically, a greater shielding 
effect is required and is accomplished by directing addi- 
tional inert gas (defined herein as shield gas) around the 
outer surface of the orifice member and across the ori- 
fice thereof to provide a total inert atmosphere at the 
weld zone. This additional inert (shield) gas may be the 
same type of inert gas and received from the same 
source as the orifice inert gas, if desired. Or, the addi- 
tional inert (shield) gas may be a different or same gas 
received from a second inert gas source, if desired. 
The quality of the constricted plasma arc column 
(formed by interaction of the inert orifice gas and the 
electric arc) depends on the type of inert gas used as the 
(orifice) gas, the tip configuration of the electrode, the 
size, shape and condition of the constricting orifice and 
the volume of orifice gas directed from the torch body. 
In the present invention, a secondary inert gas (de- 
fined herein as a secondary orifice gas) is directed 
through a hollow electrode to coact with the arc to 
produce equivalent defect free welds in types and thick- 
nesses of metals (ferrous and non-ferrous) with less total 
heat input per inch of weld (i.e. less current/voltage 
output and/or high travel speeds). The completed weld 
is more narrow with greater penetration at any given 
35 
40 
45 
50 
55 
60 
65 
- _  
tern at-the weld joint. 
The secondary orifice gas channeled through the 
electrode could be any one of the inert gases or semi- 
reactive gases or a mixture of two or more depending 
on the material being welded and the results desired. 
It is, therefore, an object of the present invention to 
provide an improved plasma arc welding torch. 
It is a further object of the present invention to pro- 
vide such a plasma arc welding torch which utilizes a 
secondary inert gas in conjunction with a primary inert 
gas to provide a substantially ’“stiffer’’ arc from the 
electrode of the torch than a typical single inert gas 
provides. 
It is yet a further object of the present invention to 
provide such a plasma arc welding torch with an elec- 
trode having a longitudinal passage therein through 
which the secondary inert gas is directed. 
BRIEF DESCRIPTION OF DRAWINGS 
FIG. 1 is a side elevational view of the torch head of 
the present invention. The torch head is shown to be 
provided with external threads onto which a shielding 
gas cup is threadably secured. The shielding gas cup is 
shown in dot-dash lines so that the grooved external 
threading of the torch body may be better illustrated. 
FIG. 2 is a partial longitudinal sectional view of the 
welding torch body of the present invention. 
FIG. 3 is a sectional view taken along line 3-3 of 
FIG. 2. 
FIG. 4 is an elevational diagrammatic view of the 
forward portion of the torch body and illustrates the 
relative flow directions of the primary and secondary 
plasma gas as well as the flow direction of the shield 
gas. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENT 
As seen in FIGS. 1 and 2, a plasma arc welding torch 
10 includes a body 12 having a shielding gas cup 14 
disposed around the forward potion 16 thereof. Cup 14 
includes internal threads 18 which threadably engage 
external threads 20 provided on the forward portion of 
the body. The external threads 20 are provided with 
grooves 22 (FIG. 1) transversely there across for rea- 
sons explained hereinbelow. 
As seen in FIG. 2, the forward portion 16 of body 12 
is provided with an annular cooling chamber 24 
through which a coolant, such as water, is circulated. 
The water enters chamber 24 through a passage 27 
provided in an aft portion 26 of body 12 and communi- 
cating with channel 24. The water exits the chamber 24 
through a passage 28 provided in the aft portion 26 of 
the body and disposed in communications with channel 
24. In i i e  manner, a shield gas passage 29 is provided in 
the afi portion 26 of body 12 to direct a shield gas from 
a source (not shown) to the external surface of the for- 
ward portion 16 (head) of torch 10. The shield gas flows 
3 
5,399,831 
4 
through the passage 29 and exits the torch body 
through an orifice 30 positioned adjacent to and on the 
aft side of threads 20. The shield gas is directed through 
grooves 22 (FIG. 1) in threads 20 for flow around the 
forward portion (head) of the torch. The shield gas is 5 
maintained in contact with the torch head by cup 14 as 
the gas is continuously flowed over the head and exits 
cup 14 through an opening 32 in the forward end 34 
thereof. 
electrode 36 is mounted in the body 12 and includes one 
end 38 which is disposed for connection to a source of 
As can be further seen in FIG. 2, an elongated hollow 10 
electrical power (not shown). The electrode 36 includes 
a second end 40 which terminates in the forward por- 
tion 16 of body 12. An annular thermally and electri- 
cally insulating support member 42 housing passages 43 
therein supports electrode 36 in the forward portion of 
body 12. 
To direct the flow of the primary inert orifice gas 
through the torch body, a passage 48 is provided in the 
aft portion of body 12 in communication with an annu- 
lar chamber 50 in the forward portion of body 12 and a 
source primary inert gas. Primary inert orifice gas is 
directed through passage 48 of body 12, and the pas- 
sages 43 of support member 42 and into chamber 50 for 
flow around forward portion 40 and tip 46 of electrode 
36. 
To direct the secondary inert orifice gas through 
body 12, electrode 36 is provided with a longitudinal 
passage 52 which is disposed in communication with a 
source of secondary orifice gas (not shown). The sec- 
ondary orifice gas exits passages 52 at the tip of the 
electrode and exits body 12 through an orifice 47 in the 
forward portion of body 12. 
It is understood that although a single inlet passage 48 
is shown and described as used in directing the primary 
gas to the forward portion 40 of electrode through 
passages 43 of support member 42, other passage means 
may be resorted to, if desired. For example, the torch 
may be provided with a single or plurality of longitudi- 
nal passages in the body which communicates with the 
source or primary inert orifice gas and chamber 50 
(other than through passage 43) whereby the primary 
inert orifice gas may be routed directly into chamber 50, 
thereby eliminating the need for passages 43 in support 
member 42. 
It is to be understood that the secondary plasma gas 
referred to herein may be any of the inert gases or semi- 
reactive gases or a mixture of two or more gases of 
these gases. The choice of gases is dependent on the 
material being welded and the results desired. The pro- 
cess can be applied to Direct Current Straight Polarity 
and Variable Polarity Welding Modes. 
It should be obvious from the foregoing that the 
principles of the present invention provides for a weld- 
ing process that is much less operator dependent and 
expands the capabilities for joining thicker materials 
with relatively low inputs. The present invention also 
permits the formed sections of the workpiece to possess 
more desirable mechanical and physical properties. 
Also, the welding process afforded by the welding 
torch of the present invention is more economical and 
efficient than other welding processes because greater 
welding speeds are attainable and less weld defects 
occur due to a stiffer and more controllable arc. 
It is to be further understood that although a specific 
construction has been discussed herein, it is for illustra- 
tive purposes only and various modifications of the 
appended claims will be readily apparent to those 
skilled in the art without departing from the spirit and 
scope of the claims. 
w e  claim: 
1. A plasma arc welding torch comprising: 
a body having aft and forward end portions; 
an electrode supported in said body, said electrode 
having an aft portion and a forward portion includ- 
ing a tip, said tip positioned in said forward portion 
of said body, and, said electrode disposed for pro- 
ducing an electric arc from said tip; 
first passage means provided in said body and dis- 
posed for communication with a source of primary 
inert gas plasma producing gas for directing said 
primary inert plasma producing gas across said tip 
second passage means being a longitudinal bore 
within said electrode, said longitudinal bore having 
a first end disposed for communication with a 
source of secondary inert plasma producing gas, 
and a second end for directing said secondary inert 
plasma producing gas out of said tip of said elec- 
trode for mixing with said electric arc and said 
primary inert plasma producing gas; and 
shielding gas means including third passage means 
disposed in communication with a source of shield- 
ing gas to direct said shielding gas around said 
forward portion of said torch body to provide an 
inert atmosphere at the weld zone adjacent said tip. 
2. A plasma arc welding torch as set forth in claim 1 
including a shield member positioned around said for- 
ward portion of said body for retention of said shielding 
gas means in contact with said forward portion of said 
body, and passage means provided in said body to direct 
45 said shielding gas means between the outer surface of 
said forward portion of said body and said shield mem- 
ber. 
3. A plasma arc welding torch as in claim 2 including 
cooling means for providing a cooling effect to said 
4. A plasma arc welding torch as set forth in claim 3 
wherein said cooling means is defined by an inner annu- 
lar cooling chamber in said forward portion of said 
body and passage means extending from said rear por- 
55 tion of said body to said cooling chamber, said passage 
means disposed for connection to said cooling source 
for directing coolant into and out of said cooling cham- 
ber. 
l5 
2o 
25 of said electrode; 
3o 
35 
40 
50 forward portion of said body. 
* * * * *  
60 
65 


Ternary gas plasma welding torch

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