The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material

Milly, Peter F., Sr.

Morris, Timothy B.

White, J. Kevin

English

NASA Technical Reports Server

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US005302805A 
United States Patent [HI 1111 Patent Number: 5,302,805 
Morris et al. [MI Date of Patent: Apr. 12, 1994 
Appl. NO.: 70,132 
Filed: May 27,1993 
Int. Cl.5 ................................................ B23K 9/12 
U.S. C1. ................................................ 219h37.71 
Field of Search ............. 219A37.2, 137.7, 137.71, 
219A24.34, 137 PS, 121.47; 228/11, 244 
References Cited 
FOREIGN PATENT DOCUMENTS 
2754580 6/1979 Fed. Rep. of Germany ... 219/137.7 
60-56481 4/1985 Japan .............................. 219/124.34 
3-248775 11/1991 Japan ............................. 219/137 PS 
[54] WELDING WIRE PRESSURE SENSOR Primary Examiner-Clifford C. Shaw 
[75] Inventors: Timothy B. Morris, Scottsboro; Peter 
F. Milly, Sr.; J. Kevin White, both of 
Huntsville, all of Ala. 
The United States of America as 
represented by the Administrator Of 
the Aeronautics md Space 
Administration, Washington, D.C. 
ASSEMBLY Attorney, Agent, or Firm-Robert L. Broad, Jr.; Guy M. 
Miller; John R. Manning 
I571 ABSTRAa 
The present invention relates to a device which is used 
to monitor the position of a filler wire relative to a base 
material being welded as the filler wire is added to a 
welding pool. The device is applicable to automated 
welding systems wherein nonconsumable electrode arc 
welding processes are utilized in conjunction with a 
filler wire which is added to a weld pool created by the 
electrode arc. The invention senses pressure deviations 
from a predetermined pressure between the filler wire 
and the base material, and provides electrical signals 
responsive to the deviations for actuating control mech- 
anisms in an automatic welding apparatus so as to mini- 
mize the pressure deviation and to prevent disengage- 
ment of the contact between the filler wire and the base 
material. 
Assignee: 
16 Claims, 1 Drawing Sheet 
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AUTOMATIC WELD1 NG ASSEMBLY I 
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U.S. Patent Apr. 12, 1994 5,302,805 
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1 
WELDING WIRE PRESSURE SENSOR ASSEMBLY 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Stat. 435; 42 U.S.C. 2457). 
BACKGROUND OF THE INVENTION 
5,302,805 
1. Field of the Invention 
The present invention relates generally to automatic 
welding systems wherein human intervention during 
operation is to be minimized. More specifically, the 
invention is a sensing device for the automatic position- 
ing of a filler wire relative to a base material being 
welded. 
2. Description of Related Art 
The current method used to maintain a correct posi- 
tioning of a filler wire on otherwise automated welding 
systems is by use of a human operator who manually 
positions the filler wire as he visually monitors its 
contact with the base material. This is a very difficult 
and tedious task, particularly during long welds which 
require a great deal of precision. The operator of such 
systems must view the weld area through a protective 
lens due to the intense arc light. From a restrictive 
viewing position, the operator must visually position 
the filler wire and must interpert the force being exerted 
by the filler wire upon the base material by observing 
the deflection in the wire. This procedure is inaccurate 
and inconsistent at best due to typical operator error, 
operator fatigue and to the varying judgment and reac- 
tion time of different operators. Prior to this invention, 
welds reauired to be uerformed in a limited mace which 
contact between the filler wire and the base material, 
thereby eliminating the need for manual weld wire 
positioning and providing a high quality weld. 
It is therefore an objective of this invention to over- 
5 come limitations of the existing art by use of a unique 
pressure sensor assembly which provides signals for the 
automatic positioning a filler wire relative to a base 
material being welded. 
It is another objective of this invention to provide a 
10 welding wire pressure sensor assembly which is capable 
of providing accurate signals for the automatic position- 
ing of a welding filler wire so as to provide a great 
improvement in the consistency and quality of the 
welds being formed. 
These and other objectives of the invention will be 
apparent to one skilled in the art from the following 
detailed description of a specific embodiment thereof. 
BRIEF DESCRIPTION OF THE DRAWINGS 
The drawing is a sectional view of the invention 
shown as diagrammatically connected to an automatic 
welding assembly. 
DESCRIPTION O F  PREFERRED EMBODIMENT 
Referring now to the drawing, the welding wire 
pressure sensor assembly which is the subject of the 
invention, is referred to generally by the reference nu- 
meral 10. This assembly consists of a base 12 which is 
3o mounted to a position controller 13, as illustrated dia- 
grammatically by the dashed connector line 15. The 
position controller 13 is part of an automatic welding 
assembly 17 which is the basic assembly to which all 
illustrated welding apparatus is attached. It is to be 
,< understood that the position controller 13 of the auto- 
2o 
25 
J J  
matic welding assembly 17 is capable of positioning the 
would accomm&ate a could 'not utilize welding wire pressure sensor assembly 10 in response to 
certain welding processes because a human operator electrical signals. Such controllers, are well known in 
was required to position the filler wire manually. E ~ ~ ~ -  the art of automated welding systems, and are utilized in 
tanks and other vessels. which are performed by such systems. The base 12 
includes a base pivot 14 and a base distal end 16. A 
connector 18 extends from the distal end 16 and is 
The present invention relates to a device which is threaded for connection to the automatic welding as- 
used to monitor and control the position of a filler wire 45 sembly 17. A tip n~chanism 20 includes a tip body 28 
relative to a base material being welded, as the filler having a t h ~ ~ d e d  opening 30 for reception of a 
wire is added to a welding The device is applica- threaded tip member 32. The body 28 also includes a tip 
ble to automated welding systems wherein nonconsum- pivot 22 and a tip distal end 24, and is attached to the 
able electrode arc welding processes are utilized. In base 12 by a Pivot Pin 26 which Passes through the base 
these systems, a filler wire is added to a weld pool cre- 50 Pivot 14 and the tip pivot 22. A base liner 34 is rigidly 
ated by the electrode arc. Examples of welding pro- fitted to base 12 and Passes through the COnneCtor 18 
cesses ofthis type include Plasma Arc Welding (PAW), and the base distal end 16. A tip liner 36 is rigidly fitted 
Variable Polarity Plasma Arc Welding (VPPAW), and to the tip mechanism 20, and passes through the distal 
Gas Tungsten Arc Welding (GTAW). In performance end Portion 24 and the tip member 32. A filler wire 38 
of these processes, a filler wire contacts the base mate- 55 passes through the base and tip liners 34 and 36 respec- 
rial being welded just ahead of the weld pool as the tively and is slideably fitted therein. AS illustrated dia- 
filler wire is being fed into the weld pool. To provide a grammatically by the dashed connector line 25, the 
precision weld, it is important that the filler wire be filler wire 38 is fed through the welding wire pressure 
correctly positioned and that it remains in contact with sensor 10 by an automatic wire feeding mechanism 19 of 
the base material being welded within a predetermined 60 the automatic welding assembly 17. It will be noted that 
range of applied pressure. The purpose of the present the filler wire 38 contacts a base material 40 immedi- 
invention is to automatically sense pressure deviations ately adjacent a welding pool 42. The welding pool 42 
from a predetermined pressure between the filler wire is formed in the base material by the action of an arc 44 
and the base material, and to provide electrical signals emitting from an electrode 46. As diagrammatically 
responsive to the deviations, for actuating control 65 illustrated by the dashed connector line 21, the elec- 
mechanisms in an automatic welding apparatus. In re- trode 46 is a part of the automatic welding system 17. 
sponse to these signals the control mechanisms position As denoted by the directional arrow adjacent the lower 
the filler wire so as to prevent disengagement of the end of tip member 32, the automatic welding assembly 
ples of such limited space areas include the areas inside 40 the performance of many of the automatic operations 
SUMMARY OF THE INVENTION 
3 
5,302.805 
17 carries the electrode 46 and the wire pressure sensor 
10 along the base material from left to right. 
When in proper welding position the wire 38 moves 
along the base material 40 creating a force F as denoted 
at the lower end of the filler wire 38. The force F is 
created as a pressure is applied to the wire 38 it is 
pressed againast an edge 48, which is the leading edge 
of the weld pool 42. This force generates a clockwise 
moment of the tip mechanism 20 about the pivot pin 26. 
In order to measure this moment a pressure sensitive 
device, such as an electric load cell 60, is positioned so 
as to measure the pressure exerted on the load cell 60 by 
the cloclwise movement. Additionally, it will be noted 
that the force F is transmitted upwardly by the wire 38 
and presses the wire against the back side 50 of the tip 
liner 36. This force translates to a frictional drag be- 
tween the tip mechanism 32 and the wire 38. Thus, as 
the wire 38 is fed through the tip mechanism 20, the 
frictional drag of the wire 38 on the tip mechanism 
causes a downward force on the tip mechanism which 
adds to the clockwise moment about pivot pin 26. 
Load cells such as are utilized in this invention are 
commercially available. In operation, a typical load cell 
is excited by an external power supply and provides an 
electrical output which is proportional to the pressure 
applied to the cell. The output of the cell is utilized to 
provide signals for actuation of a controller such as is 
commonly used in automated systems. 
As illustrated in the drawing, the load cell 60 is ex- 
cited through an electrical conductor 61 by a power 
supply 63. The signal output from the load cell 60 is 
transmitted via conductor 65 through an amplifier 67 
and finally to the position controller 13. A temperature 
compensator unit 69 is included in the output circuit of 
the load cell 60 and is located adjacent thereto to elec- 
trically correct the output signal of the load cell 60 for 
variations in ambient temperature which typically ac- 
company the welding process. 
Three adjustable screws 62, 64, and 66 are utilized to 
control and adjust the operation of the load cell 60. The 
screw 62 is utilized to directly actuate the load cell 60 in 
response to rotation of the tip mechanism 20 around the 
pivot 26. The screw 64 is utilized to limit rotation of the 
tip mechanism to prevent an overload of the load cell 
60. And screw 66 is utilized to adjustably rotate the tip 
mechanism to apply a predetermined preload to the 
load cell. The preload of the load cell establishes the 
starting point of a range within which the load cell is to 
be operated. To permit more deflection per applied 
load, Belleville spring washers 68 are placed between 
the load cell and the base 12. 
Components utilized in conjunction with the inven- 
tion such as the amplifier 67 and the temperature com- 
pensator 69 are commercially available. 
In operation, as the wire 38 moves along the base 
material 40 the force F will be applied to the wire 38 
because of its contact with the base material at edge 48. 
As pointed out above, this force generates a clockwise 
moment of the tip mechanism 20 about the pivot pin 26. 
To measure this moment, the load cell 60 is positioned 
to measure the pressure on the load cell 60 as caused by 
the clockwise moment. After being corrected for tem- 
perature variations the signal output from the load cell 
60 is transmitted via conductor 65 through amplifier 67 
and finally to the position controller 13. As pointed out 
above, the adjustable screws 62, 64 and 66 are utilized 
for initial adjustments relating to the operation of the 
load cell 60. More specifically, the screw 62 is adjusted 
4 
to center the tip mechanism 20 with respect to the base 
12 and to directly actuate the load cell 60 in response to 
rotation of the tip mechanism 28 around the pivot 26. 
The screw 64 is adjusted to limit rotation of the tip 
5 mechanism to prevent a pressure overload being ap- 
plied to the load cell 60. And screw 66 is adjusted to 
rotate the tip mechanism so as to apply a predetermined 
preload to the load cell. The preload of the load cell 
establishes the starting point of a range within which 
The controller 13 receives the signals from the load 
cell 60 and controls the position of the assembly 10 in 
response thereto. The typical scenario for sensor opera- 
tion is to bring the wire into contact with the base mate- 
I5 rial and then to apply an additional amount of pressure 
(preload) to the wire. This pressure results in an initial 
electrical output from the load cell 60. This initial pres- 
sure is considered to be the target pressure. The control- 
ler then uses a proportional and differential (PD) algo- 
20 rithm to maintain the pressure at this value by moving 
the assembly 10 in a direction toward the electrode 46 
so as to decrease the pressure of the wire 38 against the 
contact point 48. Alternatively, a similar result will be 
accomplished if the controller is programmed to rotate 
25 the assembly 10 in a clockwise direction so as to de- 
crease the pressure. Thus, if the pressure on the wire 
increases, the assembly 10 is moved closer to the elec- 
trode 46 so as to decrease the pressure of the wire 
against the pool edge 48 until the target pressure is 
30 reached. Conversely, if pressure decreases are sensed, 
the wire pressure sensor assembly 10 is moved away 
from the electrode 46 so as to increase the pressure of 
the wire against the pool edge 48. 
Variations in the configuration of the welding wire 
35 pressure sensor assembly may be employed to achieve 
specific desired characteristics in operation. For exam- 
ple, the tip member 32 may be formed in a curved con- 
figuration thus providing increased clearance between 
the welding wire pressure sensor and the automated 
40 welding system to which it is attached. This configura- 
tion also provides a constant frictional preload within 
the tip member thus providing a preload of the wire 
pressure sensor which is desirable for certain applica- 
10 the load cell is to be operated. 
tions. 
Obviously, numerous other modifications and varia- 
tions of the present invention are possible in light of the 
above teachings. It is therefore to be understood that 
within the scope of the appended claims the invention 
may be practiced otherwise than as specifically de- 
45 
50 scribed herein. 
We claim: 
1. A welding wire pressure sensor assembly adapted 
for connection to an automatic welding and wire feed 
system comprising: 
a base disposed for attachment to said automatic 
welding and wire feed system and having a base 
wire passage therethrough; 
a tip mechanism pivotally attached to said base and 
having a tip wire passage therethrough; 
sensing means mounted between said base and said tip 
mechanism for providing signals to said automatic 
welding and wire feed system in response to a 
rotational force applied to said tip mechanism so as 
to provide a rotational bias of said tip mechanism 
about said pivotal attachment and against said sens- 
ing means and said base as a welding wire is passed 
through said tip mechanism by said automatic 
welding and wire feed system. 
55 
60 
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5,302,805 
6 
2. A device as set forth in claim 1 wherein said pivotal 
attachment is located between said base wire passage 
and said sensing means. 
3. A device as set forth in claim 2 wherein means are 
provided to apply a preload to said sensing means. 
4. A device as set forth in claim 3 wherein means are 
provided to limit application of force upon said load 
cell. 
5. A device as set forth in claim 4 wherein said sens- 
ing means is a load cell. 
6. A device as set forth in claim 5 wherein means are 
provided for amplification of the signals of said load 
cell. 
7. A device at set forth in claim 6 wherein means are 
provided for temperature compensation of the signals 
from said load cell so as to maintain accurate signals 
from said load cell under extreme variations in tempera- 
ture. 
8. A device as set forth in claim 7 wherein spring 
means are positioned between said load cell and said 
base. 
9. Apparatus for determining and detecting the posi- 
tion of a welding wire with respect to a base material 
having a weld pool formed therein by an automatic 
welding mechanism, said determining and detection of 
the welding wire resulting from interaction of said 
welding wire with the edge of said weld pool, said 
apparatus comprising: 
base means for attaching said apparatus to said auto- 
tip means movably attached to said base means: 
a welding wire passing through said base means and 
said tip means and forcibly contacting the edge of 
said weld pool so as to move said tip means with 
respect to said base means; 
and sensor means for providing control signals to said 
automatic welding system for controlling the posi- 
matic welding mechanism; 
tion of said welding wire responsive to movement 
of said tip means with respect to said base means. 
10. Apparatus as set forth in claim 9 wherein said tip 
means is rotatably attached to said base means. 
11. Apparatus as set forth in claim 10 wherein said 
sensor means is responsive to pressure applied thereto 
by said tip means as said tip means rotates with respect 
to said base means. 
12. Apparatus as set forth in claim 11 wherein said 
13. Apparatus as set forth in claim 12 wherein means 
are provided to apply a predetermined pressure to said 
load cell. 
14. Apparatus as set forth in claim 13 wherein means 
are provided to limit the pressure which may be applied 
to said load cell. 
15. In an automatic welding and wire feed system in 
which a weld pool is formed in a base material during a 
2o welding process, a welding wire positioning mechanism 
for maintaining the tip of a welding wire adjacent said 
weld pool in aligned relation with and at a predeter- 
mined set pressure relative to a point on said base mate- 
rial, comprising: 
support means for supporting said welding wire in 
said aligned relation with said point on said base 
material; 
and sensing means for sensing deviations from said 
predetermined set pressure, said sensing means 
disposed for providing electrical signals responsive 
to said pressure deviations, whereby said automatic 
welding and wire feed system compensates for said 
deviations from said predetermined pressure by 
corrective movement of said support means. 
16. A device as set forth in claim 15 wherein said 
5 
lo sensor means is a load cell. 
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sensing means is a load cell. * * * * *  
40 
45 
50 
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60 
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Welding wire pressure sensor assembly

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