CA1093649A - Continuous tig welding of intermittent tabs of a tubular armature - Google Patents

Abstract

ABSTRACT
Non-continuous forms are welded on an automatic device using a continuous welding process (e.g., Tungsten Inert Gas Process (TIG) with a continuous welding arc. The noise level of the welding system is below that which is prescribed by the Operational Safety and Health Act (OSHA).
The device includes means for indexing and positioning the non-continuous forms relative to the welding electrode. The device further includes means for chilling the non-continuous-forms during the welding process, and means for periodically shunting the welding arc away from the non-continuous forms so as to maintain a continuous welding arc.

Description

- - - - - - -1. Field of the Invention -, ,,, _ 16 This invention relates to electric arc welding-17 and, more-particularly,- to--electric-arc welding using a -18 continuous arc with inert gas shielding.
19 2. Prior Art This type~,of-welding, i.e., elec~ric arc welding 21 With inert gas shielding, is well known in the prior art.
22- It is often--referred to as-a continuous welding process and 23 is--generally used for welding continuous-forms. The restriction 24-in-`use of this type of welding stems from the-fact that the-25-noise produced-by the HF current used to-initiate the-arc 26 for this-type of welding, when used for welding non-continuous 27 members, runs almost continuously and generates noise that 28 exceeds the level prescribed by the Operational Safety and ~ .., ~9 3~

1 Health Act, hereinafter called OSH~.

2 As is well known to those skilled in the art, OSHA

3 is the National Agent which regulates noise level in industrial

4 plants and factories. Generally, the regulation is such

5 that the noise is kept below the level where it will damage

6 human hearing. In a recent directive issued by OSHA, noise

7 level has to be equal to or less than 85 decibels (i.e.,

8 <85dba). If the noise level exceeds this standard, workers

9 in the vicinity of the noise creating means must wear hearing

10 protection or the noise producing means must be contained

11 within a sound proof enclosure.

12 Whenever the TIG process is used for welding

13 continuous forms, the noise which is generated by the TIG

14 welder is within the noise level prescribed by OSHA. However,

15 when this process is used for welding non-continuous forms _16 the noise level generated by the HF starting current exceeds 17 the-OSHA requirement. --In order to satisfy the OSHA standard, 18 the user must resort to either sound proofing or equip 19 workers in the vicinity of the welder with hearing protection.
20 Either approach significantly increases the cost to the user 21 which, in turn, increases product cost. As a result, this 22 type of welding is not used.
23 In order to appreciate and understand the noise 24 problem created by the TIG process, a synopsis of the TIG
25 welder operation will be given. Generally, a TIG welder 26 incorporates two separate and distinct circuit systems, a 27 high frequency start circuit and an AC or DC circuit. The function 28 of the HF circuit is to initiate the welding arc. Once the .'~

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1 arc is initiated, the welder automatically switches and 2 runs on the DC or AC circuit.
3 As is well known to those skilled in the art, the 4 high frequency circuit is a noise producing circuit. In 5 fact, the noise created by the high frequency circuit is 6 outside of the range prescribed by OSHA. However, this 7 circuit i8 operational only momentarily, i.e., to initiate 8 the welding arc, and, therefore, the human ear does not 9 recognize the noise. As such, the OSHA standard is not 10 violated. Once the arc is initiated, it will remain continuous 11 if welding is done on a continuous form. The arc is continuous 12 and it is sustained by the DC or AC circuit in the welder.
13 As'was stated, the DC or AC circuit produces a low level ... . _ _ 14 noiYe which is within tolerable levels.

1~ ' '~Howe'ver, if the welding i~ done on a non-continuous ., LO form ~ on an intermittent surface, the welder i5 always 17 operating in the start mode which is noise producing.

18 Stated another way, in welding an intermittent surface or 19 form the high freguency circuit initiates the arc . However, 20 before the running of the welder is transferred to the 21 control of the DC or AC circuit the arc is lost. As such, 22 the system ls forced to run in a start mode and produces 23 intolerabl6 noise.

24 In addition to the noise problem discussed above, 25 the weld joint which is produced by the welder when it is 26 running on the high frequency'circuit is less than satisfactory 27 and separates guicker than a joint which is formed by the 28 welder when it is running on the DC or AC circuit. This ~93~ ~

1 result stems from the fact that when the system is running 2 on the DC or AC circuit there is a steady flow of electrons, 3 for a sufficient time, from the welding electrode to the 4 members to be welded to create a homogenious joint. However, 5 when the welder is running on the high frequency circuit, 6 the flow of electrons is intermittent, which results in the 7 creation of an unsatisfactory weld joint due to crystalization.

9 The present invention solves the prior art problems 10 by a unique apparatus and method which allows the use of the Il TIG process for welding and maintaining the noise level of 12 the welder below that which is prescribed by OSHA.
13 More specifically, the article-to be welded is-14 seated on the mandrel of a positioning means. The mandrel 15 is maintained at an electrical-ground potential.~ A clamp -

16 means having an electrical ground plane is affixed to the

17 article. A TIG welder having an adjustable electrode is -

18 then positioned within arcing distance of the members to be -

19 welded. By activating the apparatus, the positioning means

20 position members to be welded relative to the electrode. A -

21 welding arc is initiated and a first electrical path is;-

22 established between the electrode and the members to be

23-weld~d. As soon as that member is transported from the

24 vicini~y of the electrode, a second electrical conducting

25 path is established between the electrode and the~ground-

26 plane. The net effect is that a continuous arc is created

27 since there is always a conducting path between the electrode

28 and ground. This, in turn, keeps the noise level within 1 acceptable range. In another embodiment of the invention, 2 only a single electrical grounding means inter-connects the 3 article and ground.
4 The foregoing and other (objects), features and advantages of the invention will be apparent from the following 6 more particular description of preferred embodiments of the 7 invention, as illustrated in the accompanying drawings.

9 FIGURE 1 is a perspective view of an article constructed in accordance with the teachings of the present 11 invention~
12 FIGURE 2 is a perspective view of a device for weld-13 ing in accordance with the present invention.
14 FIGURE 3 is a cross section of the work piece to be welded and is helpful in understanding the disclosed invention.
16 FIGURES 4A and 4B, in which FIGURE 4A appears out of 17 sequential order on the same sheet as FIGURE 1 depict the mandrel 18 and clamp assembly which forms the mechanism for inter-connect-19 ing the article of FIGURE 1 with the electrical ground potential.
DESCRIPTION OF T~E PREFERRED EMBODIMENTS
21 The present inventicn provides an apparatus means 22 and fixture in which a continuous welding process is utilized 23 for welding non-continuous or intermittent forms without 24 producing the undesirable effect which is customarily associated 25 whenever the present process i8 used for welding non-continuous 26 forms in the prior art. Although the invention is applicable 27 for welding any non-continuous forms, the invention will be 28 demonstrated within an environment where the tabs of a motor BOg76028 - 5 -1~3~

1 armature is being welded. As such, the description of the 2 invention, in accordance with the welding of armature tabs, 3 is only illustrative and does not limit the scope of the 4 invention since this process is intended to be used in any 5 situation where non-continuous forms are welded.
The Article 7 FIGURE 1 i8 a perspective view of a tubular armature 8 10 whose end portions, 12 and 14, are welded in accordance g with the present invention. Each end portion comprises a 10 plurality of tabs. For example, end portion 12 comprises 11 tabs 1,2,3,4...n. Similarily, end portion 14 comprises tabs 12 A,B,C,..n. Each tab is separated by spacing 16 and 18, 13 respectively. A more detailed description of armature 10 is 14 given in U.S. Patent 3,634,708 issued to Gene Allen Fisher 15 and assigned to the assignee of the present invention.
16 Additionally, this process may be used for welding pancake 17 armatures as well a~ the present tubular armature.
18 As will be explained hereinafter, in order-to weld 19 tab 1 or tab 2 or tab A or tab B, an arc is generated and-is 20 directed from a welding electrode to the selected tab. Once 21 that tab is welded, armature 10 is indexed and one of the 22 spacings, 16 or 18, i~ then positioned in operable proximity 23 to the electrode. Since the arc cannot be maintained between 24 the electrode and the space, the arc extinguishes itself.
25 As soon as another tab is positioned, relative to the electrode, 26 the arc is again initiated. It is this con~tant initiation 27 of welding arc which makes this process unacceptable for 28 welding non continuous or intermittent forms.

1093~'19 .
1 Armatures of the type shown in FIGURE 1 are fabricated 2 from two cards, each made by laminating a copper sheet to a 3 suitable backing member, for example, glass fibre backing. A
4 pattern of conductors are formed by chemical etching the 5. copper from the backing at predetermined intervals. The 6 backing is removed from the end portions 12 and 14 (FIGURE
7 1) of these conductors to provide the areas which will be 8 welded. This area is referred to as tabs. The cards are g then placed, one on top of the other,.such that the glass fibre 10 from the inner card forms the inside diameter ~I.D.) of the 11 tubular armature and the glass fibre from the outer card 12 insulates the cards from each other.. The conductors are 13 related so that when the ends are welded a coiled armature 4. is formed. After proper alignment,. they are glued together i5 around_a mandrel of proper-diame-ter ana-.the tabs are-welded--16 in accordance..with the present invention to ~orm an armature.
17 -A more detailed description of the manufacturing process.for.~
. ~ .
18-a tubular-.armature. i9 given in:U.S `..-Patent 3,650,021 which .
l9 is~assigned t-o the assignee of the-present invention; whiie --20 a detailed description of manufacturing process for a flat -21 or pancake armature is given in.U.S. Patent 3,312,846 issued ..

- 22 to Jac~ues Henry.Baudot:.

. 23 : - The Welding Apparatus 24.- FIGURE ~ shows a perspecti-ve.-view of-the~welding -25 apparatus which is.used for welding the tabs-of the armature 25 shown in FIGURE l. The apparatus-includes a fixture 20 and 27 welding means 22. Welding means 22 is a conventional TIG

28 welder. Since TIG welders are well known in the prior art, . BO976028 - 7 -!

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1 a detailed description of their configuration or operation 2 will not be given hereinafter. Suffice it to say that the 3 TIG welder includes a high frequency circuit which is used 4 for initiating a welding arc and an AC or DC circuit which 5 sustains the arc for welding a~ter it has been initiated.
6 The welder also includes switching circuitry wh~ch automatically 7 switches operation from the high frequency circuit to the DC
8 or AC circuit once the welding arc is initiated. Welding g means 22 includes a welding electrode 24 which has movement 10 in the directions shown by arrows 26, 28 and 30 respectively.
11 Welding means 22 is positioned relative to Fixture 20. By - 12 orienting welding electrode 24, the electrode is positioned 13 within arcing distance of the article or tab to be welded.
14 Still referring to FIGURE 2, Fixture means 20 is 15 operably associated with the welding means 22 and is used to--, -16 position a work piece in proximity with the welding electrode 17 for welding. Fixture 20 includes a frame 32, with end 18 portions 34 and 36 attached to said frame., Shaft 42 is 19 interconnected to end portion 36 via a spring-loaded connector, 40. With this spring loaded connection, shaft 42-has movement 21 in the direction shown by arrow 110. As will-be discussed 22 later, the movability of shaft 42 allows mandrel 44, upon 23 which the armature is positioned for welding, to be removed 24 and inserted in Fixture 20. Connecting means 46-is attached 25 to the free end of shaft 42. This connecting means functions 26 to receive one end of mandrel 44. The other-end of mandrel _ 27 44 is attached to connecting means 48 which is seated upon 28 end portion 34.

3~as 1 In order to rotate or position the individual tabs 2 of armature 10, relative to welding electrode 24, mandrel 44 3 is driven by a variable speed motor 50 which is connected to 4 a speed reducing means 52. The motor and speed reducing 5 means is coupled to the mandrel shaft via connecting means 48.
6 Any conventional variable speed motor with suitable motor ' 7 speed control ~4a can be used for driving mandrel 44. In 8 the preferred embodiment of this invention, a variable speed g motor, having an average speed of 1200 revolutions per 10 minute, was used. This speed reducer.has a.150 to 1 gear.
11 reducing ratio. This means that the mandrel, with its 12 associated work piece, is driven at an approximate speed o~
13 11 reYolutions per minu~e. As such, each end o'f each-armature -14 requires an approximate-time-o-~-~ive seconds-for welding'.
15'~his method-of welding'is more efficient-tha~--manual methods ~
16 such as puls~ arc or resistance welding which requires 17 approximately 1 sec.-per tab._ Of course,-it 'is within the -lB skil} bf the art.to vary the speed and setting ~f the motor---19 and its speed reducer to achieve a faster-or slower'rate-of----i .' 20 welding without departing from the scope of this invention. .
Zl Still.referring to FIGURE-2,-in order to weld the ~
22 tabs which.are associated with end-portion..1-4 or-12 -SFI~URE~
23-'~ armatur~ l0-is seated on mandrel 44. Fixture means 54,-'' -' -- -;
24 which is a chill-Iing and a grounding means,~-is-attached-to: ' Z5 encircle armature 10. The combination,:that.is Fixture 54, 26 armature 10,.and mandrel 44, is connected-to Fixture 20 at ~
27 connectors 48 and 46 respectively. The welding electrode 24 28 of welding means 22 is then adjusted to be within arcing al~

1 distance of end portion 14. As the welding means i8 turned 2 on, a supply G of monatomic gas enshrouds the tip of the 3 welding electrode and the tabs to be welded. The presence 4 of the gas ensures that the weld is not contaminated as a 5 result of chemical reaction or foreign elements from the 6 surrounding atmosphere. The detail of Fixture 54 is discussed 7 hereinafter; suffice it to say that in order to ground the 8 fixture, a spring loaded brush 56 rides on ring 58. Ring 58 9 is the grounding ring for the fixture. Spring loaded brush-10 56 is grounded via connecting means 60 through the welding 11 means 22. Another spring loaded brush, 62, rides upon 12 mandrel 44 and operates to define a second conductive path 13 between the mandrel and ground. In operation, either Fixture 14 54 ~r Mandrel 44 may be ~rounded, howeverj in some applications -15 only onç of the two, and-not both,:is grounded.
16 Referring to FIGURE 3, a sectional view of mandrel 17 44,-with armature lO and Fixture 54 is shown. Tab A, which 18 is associated with end portion-14 of armature 10, is positioned 19 relative (that is within arcing distance) of electrode 24.
20-As soon as welding means 22 tFIGURE 1) is turned on, an arc 21 i~ generated between electrode 24 and-Tab-A in the direction 22 shown-by path 64. The arc remains on-momentarily until tab 23 A is welded. However, as the armature i~-rotated by the 24 drive means passing the electrode,-a blank~-space-j--for-example 25 18 (FIGURE-l), is then positioned under the welding electrode.
26 As is well known in basic electrical theory, electrons tend 27 to flow along a path of least resistance. This being the 28 case, a second conducting path is generated between the 1~93~

1 electrode and Fixture 54 or Mandrel 44. This second conducting 2 path is identified by arrow 66. As soon as the space 3 is rotated past the electrode 24, the arc again will be 4 between the new tab and the electrode along path 64. This 5 process is alternated, that i~ electrons continue to flow 6 along path 64 and 66 until the tabs on armature 10 are 7 welded. In order to create a conducting path between the 8 conductors to be welded, both mandrel 44 and Fixture 54 are 9 grounded. Of course, the device can be operated with either 10 the Fixture 54 or the mandrel 44 grounded. However, it is 11 determined that by grounding both the Fixture and the Mandrel, 12 the quality of the welded joint is superior to the joint 13 created when only the Mandrel or the ~ixture is grounded.
14 By creating dual conducting paths, once the arc is initiated 15 it is maintained continuously and, therefore, the welder can 16 be operated on the DC or AC circuit without generating 17 undesirable high frequency noise.
18 Referring now to FIGURE 4A and FIGURE 4B, a perspective 19 view of mandrel 44, together with Fixture 54 is shown.
20 FIGURE 4A shows a perspective view of the back of Fixture 21 54, while FIGURE 4B shows a perspective view of mandrel 44 . .
22 sitting apax~ from the front of Fixture 54. Mandrel 44 23 includes a central portion 68 and two end portions 70 and 72 24 respectively. End portions 70 and 72 are machined so that ~
25 they can be fitted into connecting means 46 and 48 of=Fixture 26 20 (FIGURE 2). The central portion, 68, of mandrel 44 has a 27 substantially cylindrical shape. The shape is such that 28 armature 10 fits snugly onto the mandrel. Of course, it is 1~3~

1 within the skill of the art to manufacture the mandrel with 2 a shape different from the one shown in FIGURES 4A and 4B.
3 Therefore, the design of the mandrel :is dependent on the 4 shape of the work piece to be welded and merely changing the shape of the mandrel will not depart from the scope of this 6 invention. As was stated earlier, Mandrel 44 operates to 7 support the workpiece and also to define a conductive path 8 to ground. In order to achieve the electrical conducting g function, conducting rings 74 and 76 are positioned one on each end of central portion 68. Although several conducting 11 materials can be used for manufacturing the conducting 12 rings, within the preferred embodiment of this invention the 13 conducting rings were fabricated from copper. By positioning 14 the workpiece on mandrel 44 so that the portions to be 15 welded are in contact with one of the conducting rings (see 16 FIGURE 3) and then grounding the mandrel via spring loaded 17 brush 62 -(FIGURE 2), the entire mandrel is grounded whenever 18 necessary. In order to form an electrical isolation between 19 the conducting mandrel and Fixture 20, end portions 34 and 20 36 (FIGURE-2) are manufactured from insulating material.
21 Still referring to FIGVRE 4, Fixture 54 includes ~2 three separate, but identical sections identified as Portions 23 76, 78 and-80 respectively. Among other-things,--Fixture 54-24 operates as-a grounding means during a welding operation 25 when there is no electrical conduction between the workpiece 26 and the welding electrode along conducting path 64 (see 27 FIGURE 3). Stated another way, whenever space 18 or 16 is 28 positioned within arcing distance of welding electrode 24, 1093~

1 in order to maintain a continuous arc a second conductive 2 path to ground is achieved between Fixture 54 and welding 3 electrode 24 via electrical conductive path 66. In addition 4 to the conductive function, Fixture 54 operates as a chill 5 ring for maintaining the temperature of the workpiece within 6 acceptable limits. Each section of Fixture 54 is identical 7 in geometric shape and construction. As such, the description - 8 Of any section is an adequate description of all three g sections. For example, Section 76 has a substantially - 10 cylindrical geometric shape. Again,-this-shape should not 11 be regarded as a limitation on this invention. Generally 12 the shape.of the fixture will assume-the shape of the workpiece 13 to.be welded.=-In the preferred embodiment-of this invention -14 where a substantially'cylindrical armature-is welded, the ':~ ls-work fixture is-fabricated with a cylindrlcal-shape to -. '' -16 mirror that-of the cylindri-cal armature.- Howeverr in'the-..
17 situation where-:the armature~-has.a different shape, example -lg-a pancake armature,= then the geometry of the wor~ fixture would 19 be substantially-that_of-the-pancake.armature. In other 20 wordsj the shape-would mirror.that of its associated armature.
21 Still referr-i-ng..to FIGURE-4,-each-section of 22 Fixture_54 includes.two conductive--rings-82-and 84 respectively;
- 23-with one positioned on-each-end-of-the-longitudinal dimension................ -- 24 of.the fixture. Both conductive rings are interconnected-..
''' ' 25 via-a conducting plane-86.. Conducting.plane 86 is then..-..
26 connected to conducting ring 58 via.conducting means 88,- 90..
27 and 92 respectively. The front portion of the connecting 28 means are 5hown in FIGURE 4B while the bac~ portion-of the .
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1 connecting means are shown in FIGURE 4A. To complete the 2 Fixture 44, each section of said fixture is hinged together ~ by second connecting means 94 and 96 respectively. For 4 ~losing the fixture latching means 98, 100, 102 and 104 are 5 attached to end portions 80 and 76 respectively. In order 6 to close the fixture about workpiece, latching means 98 is 7 mated with latching means 104 while latching means 100 i8 8 mated with latching means 102. Again, several different 9 types of latching means can be implemented without departing 10 from the scope of this invention. By using a sectional 11 approach to design Fixture 54, each of the identical sections i2 is grounded via brush assembly 56 which rides on conducting 13 ring 58 (see FIGURE 2). By so doing, Fixture 54 is always 14 grounded to create a second electrical conductive path 15 between the welding electrode and ground. This completes 16 the detailed description of the preferred embodiment of the 17 invention-18 OperatiOn 19 In operation, a workpiece such as armature 10 20 (FIGURE 1) is seated on Mandrel 44 ~FIGURE 4). Fixture 54 21 is then operable positioned about the workpiece and is 22 latched into place via the latching means 98, 100, 104 and 23 102 respectively. The mandrel i6 then connected to welding 24 fixture 20 via connecting means 48 and 46 (FIGURE 2).
25 Welding electrode 26 of welding means 22 is then positioned 26 to be within arcing distance for welding the tabs of the 27 armature (FIGURE 2 and FIGURE 3). The workpiece is then 28 rotated in either direction shown by arrow 110 (FIGURE 2).

3~9 1 As soon as a tab is passed by welding electrode 24, said tab 2 is welded. However, as a space passes by the electrode the 3 arc is shunted to Fixture 54 or Mandrel 44. The process is 4 repeated until the workpiece is welded.
While the invention has been particularly shown 6 and described with reference to preferred embodiments thereof, 7 it will be understood by those skilled in the art that 8 various changes in form and details may be made therein 9 without departing from the spirit and scope of the invention.

11 , ~0

Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Welding apparatus for a non-continuous workpiece comprising in combination:
a welding means, having a welding electrode, for generating a welding arc;
positioning means associated with said welding means, support mandrel associated with the positioning means and electrically connected to the portion of the work-piece to be welded, said mandrel being electrically conductive to define a first electrical conductive path to ground;
second electrical conductive means placed adjacent said welding electrode to define a second electrical con-ductive path between the electrode and ground whereby the first and second electrical conductive paths operate to establish and maintain a continuous welding arc between the welding electrode and the non-continuous workpiece so as to reduce noise generated by the welding means.

2. Welding apparatus for a workpiece having electrically conductive and non-conductive surfaces comprising in com-bination:
welding means having a welding electrode at a first electrical potential for generating an electrical welding arc;
positioning means operably associated with said weld-ing means for positioning the workpiece in close proxi-mity to the welding electrode;
first conductive means electrically connected between the conductive surface of the workpiece and a second elec-trical potential; and second conductive means adjacent the non-conductive surface of the workpiece, said second conductive means supporting the workpiece and defining a second electri-cal conductive path to the second electrical potential, whereby said first and second conductive means alter-natively conduct current with the welding electrode so as to enable a continuous arc generation.

3. A welding apparatus as defined in Claim 2 wherein said positioning means comprises:
a support frame;
end connectors operably associated with said support frame; and rotatable mandrel means operably connected to the end connectors for alternatively positioning the sur-faces of the workpiece adjacent to the welding electrode.

4. A welding apparatus as claimed in Claim 3 further including:
a variable speed motor connected to said rotatable mandrel means; and means for controlling the speed of said motor.

5. A welding apparatus as defined in Claim 2 wherein the second conductive means includes a clamp operable for chilling the workpiece.

6. A welding apparatus as defined in Claim 5 wherein said clamp comprises:
a member including a plurality of sections with each section having a geometrical shape substantially equi-valent to the workpiece;
means associated with each section of said member electrically connected to the second electrical potential;
means for joining each section to form the member;
and means for locking the member so as to encompass the workpiece.

7. A welding apparatus as claimed in Claim 6 wherein said member is substantially cylindrical and fabricated from a material having relatively high heat absorbing characteris-tics.

8. A method for welding discontinuous workpiece forms with a continuous welding process comprising the steps of:
(a) positioning an arc welding means adjacent to the workpiece form;
(b) initiating a welding arc;
(c) welding one portion of the discontinuous workpiece form by maintaining the welding arc with the work-piece form to a first electrical conductive path;
(d) maintaining a welding arc through a second elec-trical conductive path during a portion of the discontinuous workpiece form that does not require a welding process; and repeating steps (e) and (d) until the entire discontinu-ous workpiece form has all of its welding portions completed.