A gas/arc electrode is disclosed for use under vacuum conditions where a first housing encloses a second housing, with an end of the second housing extending through an opening in the first housing and having an outlet orifice. Provisions are made for circulating a coolant through the first housing to surround and cool the second housing. An electrical current and a gas, such as argon, as passed through the second housing, with the current flowing through a narrow stream of the ionized gas flowing through the outlet orifice to a workpiece to be treated. The second housing forms a chamber which has a cross sectional area, in a plane perpendicular to the direction of gas flow, of at least ten times the cross sectional area of the outlet orifice such that a gas pressure can be maintained in the chamber to reduce erosion of the chamber walls

Poorman, Richard M.

Weeks, Jack L.

English

NASA Technical Reports Server

United States Patent t191 
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US005 149932A 
1 1 1 1  Patent Number: 5,149,932 
Poorman et al. [45] Date of Patent: Sep. 22, 1992 
1731 
Primi 
ARC/GAS ELECTRODE 
Inventors: Richard M. Poorman, Arab; Jack L. 
Weeks, Guntersville, both of Ala. t571 ABSTRACT 
Attorney, Agent, or Firm-Robert L. Broad, Jr.; Guy M. 
Miller; John R. Manning 
Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Appl. NO.: 677,182 
Filed: Mar. 29,1991 
Int. C l . 5  ................................................ BUK 9/24 
U.S. c1. ......................................... 219/75; 219/72 
Field of Search .................................... 219/72, 75 
References Cited 
FOREIGN PATENT DOCUMENTS 
591278 2/1978 U.S.S.R. ................................ 219/72 
85671 1 8/1981 U.S.S.R. ................................ 219/72 
A gas/arc electrode for use under vacuum conditions 
wherein a first housing encloses a second housing, with 
an end of the second housing extending through an 
opening in the first housing and having therein an outlet 
orifice. Provisions are made for circulating a coolant 
through the first housing to surround and cool the sec- 
ond housing. An electrical current and a gas, such as 
argon, as passed through the second housing, with the 
current flowing through a narrow stream of the ionized 
gas flowing through the outlet orifice to a workpiece to 
be treated. The second housing forms a chamber which 
has a cross sectional area, in a plane perpendicular to 
the direction of gas flow, of at least ten times the cross 
sectional area of the outlet orifice such that a gas pres- 
sure can be maintained in the chamber to reduce erosion 
of the chamber walls. 
zty Examiner-Clifford C. Shaw 5 Claims, 2 Drawing Sheets 
https://ntrs.nasa.gov/search.jsp?R=19920023786 2020-03-24T07:18:17+00:00Z
US.  Patent Sep. 22, 1992 Sheet 1 of 2 5,149,932 
20 
44 
Figure 1 
U S ,  Patent Sep. 22, 1992 Sheet 2 of 2 5,149,932 
41 \\ Figure 2 
5,149,932 
1 2 
will be evacuated to a pressure of less than about 0.001 
torr, with evacuation of the chamber being continued to 
hold this low pressure as the treatment is carried out. Of 
course, if the electrode is to be used in outer space, no 
vacuum chamber is needed. 
Referring now in detail to the drawing, there is 
shown an electrode 11 made U P  of a first housing 12 
having a second housing 13 positioned therein, with the 
second-housing 13 having an end 16 extending through 
10 an opeiiing in the first housing 12 so as to be exposed. 
The housing 13 is made of a conductive material such as 
copper while the end 16 is made of a metal which will 
I .  Field of the Invention readily emit electrons at an elevated temperature, such 
This invention relates to arc/gas electrodes suitable as tungsten or tantalum. Alloys of tungsten and small 
l5 amounts of thorium, yttrium or lanthanum can also be 
2. Prior art used. 
Gas/arc welding electrodes suitable for use in a vac- The second housing 13 is smaller than the first hous- 
uum environment are known. Typically, the electrode ing 12 to form a first chamber 20 surrounding the sec- 
will be in the form of a tube through which an electrical ond housing for the flow ofa coolant around the second 
current and a gas such as argon are Passed, the tube housing. The second housing 13 forms a second cham- 
being conductive such that the electrical current can be ber 21 through which a gas such as argon can flow to 
passed through the tube to ionize the stream of gas and through an outlet orifice 17 in the end 16 of the 
exiting from the tube and thereby provide a path for the .second housing 13, 
Argon gas flows from a source 25 through a hose 26 electric arc to reach the workpiece being welded. 
A major disadvantage of this type of electrode is that 25 to a gas inlet tube 27 leading to the chamber 20. A 
there is a considerable amount of corona discharge from coolant, such as a mixture of ethylene glycol and water, 
the electrode. Under vacuum conditions and with the flows from a 3o through a hose 31 to a coolant head being heated from the flow of electricty through inlet tube 34 leading to the chamber 2o to cool the it, there is a considerable amount of erosion of the weld- electrode. A coolant outlet tube 35 leads from the ing head. This erosion will quickly eat away the end of 30 chamber 2o to a hose 36 leading to a coolant sump 38. 
the tubular electrode from which the gas flows to result It will be noticed that one of the tubes 34 and 35 in a very short operating life. terminates at one end of the chamber 20 and other ter- 
SUMMARY OF THE INVENTION miates at the other end of the chamber 20. This is to 
through this cham- 
end extending through an opening in the first housing, sufficient to maintain the temperature of the electrode at 
with the second housing having an outlet orifice in the not more than about 150 to 200 
end thereof. The housings are of different sizes such that Under certain conditions it may not be necessary to 
a coolant can be circulated through the first housing use the housing 12 and it and the associated structure for 
around the second housing to cool the electrode. An Passing a coolant through the electrode can be elimi- 
inert gas is passed through the second housing to flow nated. For example, it may under certain conditions be 
through the outlet orifice toward a workpiece to be possible to fit the housing 13 with fins (not shown) 
treated and an electrical current is passed through the which would radiate heat from the housing 13 at a rate 
second housing to ionize the gas and thereby provide a 45 sufficiently high to keep this housing at a reasonable 
path for current flow through the outlet orifice to the temperature. 
workpiece. The second housing forms a chamber which The hose 31 is Preferably a conventional arc./gas 
has a cross sectional area, in the direction of gas flow, of hose which has a conductive metallic braid built into 
at least ten times the cross sectional area of the outlet the hose for carrying an electrical current from a Source 
orifice such that a gas pressure can be maintained in the 50 40 to the electrode 11 while the hose itself carries the 
ARC/GAS ELECTRODE 
ORIGIN OF THE INVENTION 
The invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured and used by or for the Government of the 
United States of A m e ~ c a  for government purposes 
without the payment of any royalties thereon or there- 
for. 
BACKGROUND OF THE INVENTION 
for use in a vacuum environment. 
A gadarc electrode wherein a first housing encloses 35 provide for a good flow Of 
an electrical)y conductive second housing which has an ber' is passed through the at a rate 
F. 
second housing to reduce erosion of the inner wall of 
the second housing from which electrons are flowing. 
DESCRIPTION OF THE DRAWINGS 
gas/arc electrode of this invention showing the posi- 
tioning of the parts of the device. 
FIG. 2 is an enlarged fragmentary view showing how 
the ionized gas flows from the electrode to a workpiece 
DETAILED DESCRIPTION OF THE 
INVENTION 
FIG. 1 is a cross sectional view, in perspective, of the 55 
to form a path for electrical current. 60 
The electrode of this inventon is intended to be used 
under vacuum conditions for such uses as welding, 65 
cutting, heating a metal for vapor deposition, etc. The 
electrode will be positioned in a chamber (not shown) 
surrounding a workpiece to be treated and the chamber 
coolant. 
The e!ectrical source 40 is such that an initial high 
voltage of about 20,000 volts can be applied to the elec- 
trode 11 to ionize the argon gas flowing through the 
electrode to a workpiece 41 (FIG. 2) to be treated. 
After the gas stream is ionized, the voltage applied to 
the electrode 11 is dropped to about 20 volts dc, with 
the electrode being negative and the workpiece being 
positive. Such power supplies are known. 
To reduce corona discharge from the electrode, the 
lower end of the first housing is fitted into an insulator 
44 made of lava stone, with an aperture 45 being pro- 
vided in the insulator 44 to expose the tungsten end of 
the second housing 13. 
Erosion resulting from corona in the chamber 21 is 
reduced by maintaining the pressure of the gas in this 
chamber within the range of about 0.1 to 1.0 torr. This 
is made possible by the ratio of the cross sectional area 
. 
5,149,932 
3 4 
of the chamber relative to the cross sectional area of the ond housing being electrically conductive and hav- 
outlet orifice 17. The cross sectional area of the cham- ing an outlet orifice in said end, said first housing 
ber 21, in a plane perpendicular to the direction of gas being larger than the second housing to form a first 
flow, should be at least ten times the cross sectional area chamber surrounding the second housing, said 
of the orifice 17. This will allow the chamber 21 to be 5 second housing forming a second chamber, 
held at a pressure of 0.1 to 1.0 torr. This pressure, which c. means for circulating a coolant through said first 
is much greater than the about 0.001 torr in the treat- chamber into contact with the second housing to 
ment chamber, reduces erosion of the surface of the cool said second housing and said electrode, 
chamber 21 for a much longer electrode operating life. d. means for supplying a gas to the second chamber, 
and 
to and through the electrode to exit the electrode e. means for supplying an electrical current to the 
through the orifice 17 in a narrow, ionized, stream 48 second housing to ionize the gas flowing from the 
which is represented by arrows in FIG. 2, with the orifice to provide a current path from the electrode 
coolant being passed through the electrode 11 from the to a workpiece positioned adjacent to said orifice. 
source 30. 2. The electrode of claim 1 wherein the coolant is 
The initial application of a high voltage to the elec- introduced into the first chamber adjacent to one end 
trode will ionize the argon gas in the chamber 21 and in' thereof and withdrawn from a point adjacent to the 
the stream 48 impinging on the workpiece 41 (FIG. 2) other end of said chamber. 
to form a conductive path for the electrical current to 3. The head of claim 3 wherein a portion of the first 
flow from the electrode 11 to the workpiece 41. The use 20 chamber surrounding said opening in said first housing 
of the chamber 21, as compared to the conventional 
tubular electrode, allows for the pressurization of the 4. The apparatus of claim 3 wherein said insulation is 
chamber 21 to reduce erosion from the inner walls of 
In ooperation, argon gas is passed from the source 25 10 
15 
is electrically insulated. 
lava stone. 
the second housing 13 and to provide conditions under 
which the argon gas can easily be ionized. 
The voltage is then dropped and the treatment car- 
ried out. Electrons will flow from the surfaces forming 
the chamber 21 through the orifice 17 to the workpiece 
41. Because of the large surface area of the chamber 21 
and the gas pressure in this chamber, erosion of the 30 
chamber walls will be very low. 
25 
What is claimed is: 
1. A gadarc electrode comprising 
a. a first housing, 
b. a second housing positioned inside the first housing 35 
and having an end extending through an opening in 
said first housing to an exposed position, said sec- 
5. A gadarc electrode comprising 
a. a housing forming a chamber, said chamber having 
an outlet orifice for the flow of a gas from the 
chamber to a workpiece, 
b. means for supplying a gas to the chamber at a 
predetermined rate, 
c. means for supplying an electrical current to the 
housing, said chamber having a cross sectional area 
in a plane perpendicular to the direction of gas flow 
of at least ten times the cross sectional area of the 
outlet orifice, and 
d. means for bringing a coolant into contact with the 
housing to cool said housing. * * * * *  
40 
45 
50 
55 
60 
65 


Arc/gas electrode

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