USRE15313E - Arc-welding system and method of operating the same - Google Patents

Description

H. 0-. MOHTON. ARC WELDING SYSTEM AND METHOD OF OPERATING THE SAME. I

APPLICATION FILED JAN 2511922.

33 I Re1ssued Mar. 21, 1922. 3f

NI STATES PATENT. omen.

HARRY D. MORTON,.OF DETROIT, MICHIGAN, ASSIGNOB TO AUTOMATIC ARC WELDING COMPANY, 01! DETROIT, mQHIG-AN, A CORPORATION OF MICHIGAN.

- ABC-WELDING- SYSTEMAIVVD amnion or ornnarmo THE smn Specification of Reissued Letters Patent. Reissued Mar, 21, 1922 Original No. 1,392,437, dated amber 4,1921 Serial No. asasao, filed December 2, 191a. Application m reissue filed January 25, 1922. Serial No. 531,828; l

T all whom concern). Be it known that I, HARRY D. MORTON, a

. citizen of the United States, residing at'Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Arc-Welding System's and'Methods of Operating the Same, of

which the'following is a specification.

My invention relates to electric arc welding, and more particularly to automatic and semi-automatic apparatus for i this purpose and to the method ofoperating the" same.

In the drawings, Fig. lis a diagrammatic view showing one form of my invention, in V which theballistic resistance which is Qused' in the welding circuit may have ei'thera'sub-' stantially zero temperature co-efiicient in which no compensatory adjustment is re quired, or in which the'ballistic resistance has a substantialtemperature co-eflicient, in which case manually operated compensatory means are used; Fig. 2 is a diagrammatic ",view illustrating automatic compensatory means for the ballistic resistance, and Fig. 3 is also a diagrammatic view showing another form of automatic compensatory means for the ballistic resistance.

Referring to Fig. 1, current is supplied to the welding circuit from a generator or other suitable. source of current, not shown, the circuit including the wire 11, solenoid 12, wire 13, welding strip 14,'work 15, and return wire 16. It will be understood that in the welding operation an'arc is formed at a between the end of the welding strip and the groove 17 in the work 15. For the purpose of welding two plates or parts together, the ends to be joined-are tapered and placed in abutting relation, thereby forming the groove 17 and the intense heat of the are at a rapidly melts the metallic strip 14 and this molten metal is deposited in the groove 17 thereby uniting the pieces of metal at the joint 18. On account of the fact that the intense heat at the are a melts the strip 14 rapidly,it is necessary to feed this strip from a reel to the arc uninterruptedly and automatically to produce a homogeneous by an annular weld, and in order to mounted in a welding head 21, which is indicated in dotted lines, and provided with suitable guides for the welding strip, 14. The" work in the present case consists of two cylindrical members which are to be 'oined 0 this the work is rotated while the welding strip 14 is being fed to the are at a and while the molten'metal formed is being deposited in the groove 17. The cylindrical members constituting the work 15 are rotatively supported in any suitable manner, as by the center 26 and a mandrel 27. The mandrel 27 is connected by the gear 81 to a gear 80 7o keyed to the motor shaft m. It will be seen that by this arrangement the motor shaft 122. drives the feed rolls 19 and and also produces a relative movement between the work and the welding head while the strip 14 is be- 5 ing fed'to the work and the molten metal is being deposited on the work. It will also be noted that the feed rolls are driven at a higher speed than the work, since the ratio of the gears and 81 is about asl to 7 A fixed relation is preserved between the feed of the welding strip 14 and the rate ofmovement of the work 15, but the feed of the welding strip 14 is varied because the welding strip cannot be made uniform throughout its 85 entire length. Different portions of the welding strip may vary in fusibilityor be r of slightly-differing diametersand the strlp will, therefore,fuse at different rates When the welding strip 14 fuses very rapidly there 9 is a danger that the are at a may suddenly become so long as to rupture and then 1n order to start the are it is necessary to bring the end of the strip 14 again into contact with the work. Conversely, if the feed of the strip 14 to the are axis more rapid than strip may be fed against the work and cause a short circuit, which is injurious to the work and also requires separating the electrodes to a ain form an arc.

- I have j ound that under: normal conditions an equilibrium ,is maintained b the arc itself, which has, Within certain limits,

if the welding strip is continuously fed at a suitable constant rate, a compensatory actlon, as follows: When the arc shortens the resistance decreases, the amperage uses,

and this rise in amperage results in the welding strip fusing more rapidly, thereby causingthe arc to lengthen. Conversely, if the arc lengthens the resistance is increased, the amperage decreases proportionately, the weldingstrip is fused more slowly, and the continuously moving welding strip restores.

, through the shaft m the welding Strip feed; roll 20 and through gears 80, 81, the mandrel 27 supporting the work 15. In series with the armature of this motor M is the rheostat R." The arm 86 of thisrheostat tion of my device, its effect is to accentuate the self-compensatory action of the are. In

the device here shown, the motor M, which is supphedwith current from a source in- .dependent of the welding circuit, drives is connected to the armatures of the coils 84, 85. These coils 84, 85 receive their current from "an independent source, such as the battery B. In the local circuit are the two switches 0, 0. These switches are operated by the movable switch member 32 attached to the armature 30 of the control). The op-T solenoid 12 in series with the arc. eration of the device is as follows: The are is struck by first moving the weldin strip 14 into contact with the work 15 an then separating the same therefrom manu-' ally, or in any other well known manner. Thereafter the welding strip is continuously fed toward the work during the welding process. In the event of the are becoming too short, the. solenoid 12 becomes more strongly energized and its armature 30 overcomes the tension of the opposing spring 31, causing the movable switch member 32 to engage with the stationary I contact member 0, thereby establishing a local circuit from the battery B throughthe solenoid 85 and moving the rheostat arm 86 in a direction to cut in additional resistance in the resistance member R. The amount of current in the armature of the motor M is thereby reduced and the speed of the motor corre+ spondingly decreased. This reduction in the rate of feed in the welding strip 14 results n the welding strip being fused' more rapldly' than it is. fed and the arc is quickly restored to its normal length. Conversely,

accurately made.

i a similar result.

if, during the welding process, the arche- -comes unduly long, the pull of solenoid 12 is correspondingly decreased and the tension of the opposing spring 31 overcomes the;- solenoid pull, causing the movable switch member 32 to engage the stationary contact a and thereby close the local circuit from the battery B through the solenoid 84 and move the rheostat arm 86in adirection to cut out some of the resistance in the rheostat R. The amount of current in the armature of the motor M is thereby increased, the speed of the motor is correspondingly accelerated, thus causing the welding strip, l lxto be fed more rapidly than it is fused, and restoringthe are to its normal length.

Whatever arc-maintaining mechanism may be employed, the adjustment mustbe For example, I have found that where a ballistic resistance is used which has a relatively high temperature co-efiic-ient of resistance,'the fusing energy available at the arc varies materially with the temperature of this ballistic resistance R. When R is cold and its resistance 90 is low, a relatively high fusing energy is available at the arc. 'onversely, as R becomes heated and its resistance increases materially, a corresponding reduction occurs in the fusing energy available at the are. Assume that spring 31 is so adjusted that when the resistance R is at a temperature of 300 F there is available at the arc such an amount of fusing energy as to result in a substantially inormal equilibrium between the feeding rate of the welding strip 14 and the fusin rate of said welding strip. Under these con itions, if the arc shortens unduly,

the low-speed switch 0 will become operative and the arc length will be restored to normal 106 in the manner hereinbefore described. Should the arc lengthen unduly, the highspeed switch 0 will. become operative, with The corrective means will remain operative to maintain the are so long 100 asthe supply of fusing energy available at the arc is not interfered with. When, however, the temperature of the resistance reaches, say 600 F., the supply of fusing energy available at the arc will have been Ill materially reduced, with a correspondin reduction in the normal pull'of solenoi '12, and a consequent tendency on the part of spring 31 to keep the high speed switch 0' closed. The motor will thus tend to run at a highrate of speed and, therefore, tend to bring the welding strip in contact with the work, and thus produce a condition the opposite of that which is desired. Converselmj, as the resistance-R cools-.as, for example? when the machine is shut down'-the amount of fusing energy available at the arc is materially increased, with a corresponding increase in the normal pull of solenoid12, and

a consequent tendency on the part of this solenoid to overcome the tension of s rin 31. and keep the low-speed switch cose The motor will thus tend to run at a lower rate of speed and, therefore, tendto allowthe arcto become so long as to rupture, thus bringing. about "a condition the oppositeof "that which is desired. order to overcome.

" may be varied. 1

I have found that it is inconvenient to obtain a stability of adjustment by the means shown in Fig. 1, as it is often necessary to change the adjustment from time to time during the day, and from day today.

I have discovered that one cause of this difliculty is variation in the resistance of the welding circuit. I have: found that if the stabilizing means, such as resistance R and reactance C, is one whose effect is consider, ably different when hot from that exerted when cold, a sin le adjustment of screw 33 will not suflice. It is, therefore, highly desirable that the resistance B "should be one having a low temperature resistance co-efiicient. I have found the low tem erature co-eflicient alloys now on the mar et satisfactory.

Any means, however, for. rendering the resistance substantially constant in its effect may be employed to permit a substantially constant adjustment. j

In referrin to a stabilizing means constant in effect I' intend to implysuchsubstantial or approximate constancy of resistance as will permit of constancy of adjustment. It might in some cases,'for example,

be possible to do this without employing a so-called zero co-eflicientjmaterial, by using ordinary resistance grids having a normal carrying capacity so much greater than the welding current that thetemperature would not vary greatly, or artificial cooling might be resorted to, to attairi the same end by maintaining a constant temperature.

In many instances approximate compensation for temperature changes may be secured by the use of a resistance having a positive temperature co;eflicient in series with an electrolyte or other form of resistance-having a negative temperature co-efiicient. An automatic means of varying the amount of resistance in circuit so as to main- .1.a....fi.1dwinding 35 is in series the...

with. The variable resistance 9 is SllifiGlBIlt".

inmagnitudeso that, under the control of magnet 36' shunted across the circuit'inside of the resistance andreactance stabillzing means, it is able to maintain a substantially constant potential across the arc. This resistance' is shown as a carbon pile rheostat controlled by lever in response to the magnet 36 acting against the weight of the lever 37 L In Fig. 3 I have shown an automatically self-compensating resistance which may be employed. In this figure r R and r, are res stances having approximatel perature co-eflicients, and R w ich constitutes the maj or part of the stabilizing resistance, may be any convenient resistance, such as a cast iron grid, iron wire or water rheostat.- A small variable resistance, indicated as a carbon pile rheostat 9, is part of the branch containing R Resistances 1' and 1', may be of very small current carrying capacity, and hence inexpensive. The resistances are so proportioned that at normal 7 temperature there is no difference of potenwhich by worm and sector S actuate lever 37 of carbon pile rheo'stat 9. The field magnet F of this motor is connected in shunt to the circuit as shown. Its connection is zero temimmaterial, as it is onlymecessar that there should be a field, and its particu ar strength is-immaterial.

Should a change occur in the resistance R 4 a difference of otential will occur between points a and and a current will flow through the armature A whose direction will depend upon whether an increase; or a decrease in resistance'R has occurred. The armature will thereupon rotate to vary resistance 9 to restore the total resistance in circuit to normal. Any other suitable variable resistance means maybe emplo ed. All of the foregoing means, and ot ere which will sug st themselves, I intend to include as sta ilizing means constant in effect.

Another source of varying circuit resistance seems to be the varying resistance of the welding strip itself as the result of the heating effect of the welding current and of' the arc. It will be observed that the welding strip in the device herein shown, for purposes of illustration, is carried by a,

suitable guide 34 and feeding rolls 19 and 20.v The current is carried to the electrode chiefly by the lower guide or holder 34. I. have found that it is very desirable for themaintenance of a stable are, and in commercial use practically indis usable for the best results, that the electro e holder ofan are welding machine having automatic electrode feeding and are maintaining means, should be as close as possible to the arc. The reason 'for this is not entirely clear, but I have found from much experience that if the electrode holder is a considerable distance from the arc, the are becomes unstable. and diflicult to' control." For example, in a particu- A lar automatic machine, developed and built by me, I have found that with a current of 140 amperes an electrode of iron orsteel wire inch in diameter, fed at a speed of about 16. inches a minute through a holder,

such as 3, reachin to within to 5 inch of the arc, the operatlon is stable as long as the machine is kept in operation. If, however, this distance is materially increased in said machine, the length of time that the arc continues stable decreases, and if the distance. is as great as 2 or 2% inches the are is stable only for a -few seconds after the machine is started. I l

It may be that this effect is purely mechanicaland the result ofvibration resulting. from the feeding forward of the electrode strip. I have observed that this condition ofinstability accompanies the extension backward from thearc of the incandescence of the electrode and that the correct distance is to be determined in view of the diameter of the wire, the current carried,

, and the speed at which the wire is fed. This leads me to believe that the sudden increase of resistance of the wire as itreaches the temperature of recalescence, and the extenthe current to the electrode at a sion backward of such a temperature to too great a distance, is the cause of this instability. However this ma be, the fact is unquestionablyestabli'she by my experience, and I have discovered that the difiiculty can be overcome by supporting and conveying oint close to the arc, and that unless this ower elec-- trode holder is brought down rather near the are, continuous stable operation is very difiicult to secure.

It is advantageous to have this electrode guide of; suificient current carryingcapacity to avoid its being greatly heated by the current which it carries, and of good heat conducting material. A wire or rod of an inch in diameter would be melted in a short time by a current of about 90 amperes, and one of a diameter by a current of about 140 amperes, and, in general, the current employed in welding is large enough to'soon melt or raise to high incandescence the electrode used if the latter were stationary.

' Inasmuch as the wire is fed continuously forward, it does not melt except at the are, even with continuous welding, and by taking the current to the electrode near to the arc the heating to incandesoence, with its attendantf extreme changes in resistance, is

confined to a short length of the electrode. The changes of resistance are, therefore, *a

small percentage of the total resistance and do not result in instability. It will be seen, therefore, that the .,continuous feed and the point of support at which the current is taken to the electrode are features intimately related to the stability of the arc.

The lower electrode holder is preferably made adjustable to and from the work in any well known or convenient manner, in

order that the most advantageous distance from the arc may be attained for any particular circumstances of use.

While I have shown means for steadily feeding the electrode toward the work, and prefer such meansd I do not limit m self thereto, as the intermittent feeding o the electrode by short increments at frequent intervals may be substituted for the steady.

feed and by the expression continuously feeding, as used in my claims, I intend to include either a steady feed or an intermib tent feed sufliciently rapid to be equivalent thereto.

What I claim and desire to secure by Letters Patent of the United States, is:

1. In a welding apparatus, awelding tool,

a welding circuit, and a stabilizing means ing circuit.

constant in its effect included in said weld- 2. In a welding apparatus, a welding tool,

a welding circuit, and a stabilizing resistance whose resistance is independent of its temperature included in said welding, circuit. 3. In a welding apparatus, a weldingtool, a welding circuit, and a stabilizing means comprising a reactance and a resistance, said resistance being constant in its effect included in said welding circuit.

4. In a metallic electrode arc welding apparatus, a welding tool having means for, feeding the electrode toward the work, a

welding circuit, and a stabilizing means constant in its effect included in said weldmg circuit.

feeding a weldingstrip toward the work, means for supplyingelectrical energy to the 5. In a welding apparatus, means for are, and means responsive to variations in the resistance of the weldlng c1rcu1t external to the arc foi correctively varying the rate of feed of said strip.

6. In a metallic electrode arc welding apparatus, means for feeding a welding strlp toward the work, means forsupplying electrical energy to the are, stabilizing means in the welding circuit, and means associated with the stabilizing means for aocentuating the self-compensatory action of the are.

7 In an arc welding apparatus, means for continuously feeding a-metallic welding strip toward the work at a'normal rate pro portioned to the resistance of the welding circuit external to the are, means for maintaining' said proportion between the mustance of the circuit and the rate of feed, and means for controlling the relation between the fusing rate and the feedingrate of the Welding strip to compensate for variations at the arc.

8. In a metallic electrode arc welding apparatus, a' welding tool, a stabilizing resistance constant in its ,effect, and means for conveying current to the electrode at a point near the arc.

9. In a welding apparatus, a welding .machine having automatic means for continuously feeding the electrode toward the work, and a Stabilizing means Whose effect is constant.

10. In a welding apparatus, a welding tool having automatic means for continu ously feeding the.elect rode toward the work and for maintaining the arc, and a stabilizing resistance whose effect isindependent of its temperature. I

11. In a metallic electrode arc welding apparatus, a welding tool having automatic means for continuously feeding the electrode toward the work, a stabilizlng resistance whose effect is independent of its temperature, and means for conveying current to the electrode at a oint near the arc.

12. In a meta ic electrode arc Welding apparatus, a welding tool havin automatic means for continuouslyfeeding't eelectrode toward the work and for maintaining the arc a stabilizing resistance whose effect is independent of its temperature, and means Work, which consists in supplying the current to the welding strip always at a .point near the are through a stabilizing means constant in its effect. a

14. The process of electric arc welding which consists in striking an are between the work and a strip of metal constituting one electrode, stabilizing said are by supplying current to a point on the strip near the are through a stabilizing means constant in its" effect, and maintaining said are by feeding said electrode continuously and automatically toward the work.

15. In an electric arc welding apparatus, a welding tool having automatic means for continuously feeding the, electrode toward.

the work and for maintaining the arc, and a stabilizing means constant in its effect.

16. In an electric arc welding apparatus, a constant potential source of current, a welding tool having automatic means for continuously feeding the electrode toward the work. means controlled by a variable characteristic of the are for controlling the.

welding tool having automatic means for continuously feeding the electrode toward the work, means controlled by a variable characteristic of the arc for controlling the are, a stabilizing means constant in its e ffeet, and means for conveying current to the electrode at a point near the arc.

18. In an electric arc welding apparatus, a constant potential source of current, a welding tool having automatic means for continuously feeding the electrode toward. the work, means controlled by a variable 30 characteristic of the are for controlling the 1 arc, means for'adjusting said means, a stab ilizing means constant in its effect, and

means for c0nveying current to the electrode at a point near the arc.

19. In a metallic electrode arc welding apparatus, the combination with a welding tool, having means for continuously feeding a welding strip toward the work, and means for, supporting said strip at a point close to the are, of an arc stabilizingmeans constant in its effect.

20. In a welding apparatus, a welding machine having automatic meansfor feeding th electrode toward the work, and a stabilizing means whose effect is constant.

21. In an electric arc welding apparatus, a circuit having a constant resistance for supplying current to the arc, means for automatically feeding a welding strip toward the work, and means for automatically controlling the relation between thefeeding rate of the welding strip and the fusing energy of the arc.

22. The process of electric arc welding which consists in suplying current to the arc through a circuit having a constant resistance, automatically feeding a welding strip toward the work, and automatically controlling the relation between the feeding rate of the welding strip and the fusing energy of the are. y

23. In'an. electric arc welding apparatus, a circuit having a constant resistance for supplying current to the arc, and means for 116 automatically feeding a welding strip toward the work.

24. In an electric arc welding apparatus, a circuit whose resistance external to the arc is constant for supplying current to the are, 12 and means for automatically feeding a welding strip toward the work.

25. The process of electric arcweldlngwhich consists in maintaining the resistance of the circuit external. to the are constant,

and automatically feeding a welding strip arc weldjng wherein a metallic welding strip is"'ai1tomat-ica1ly fed toward the work, which consists in maintaining the resistance of the circuit external to th are constant throughout the welding operation.

27. The improvement in that method of are welding'wherein a metallic welding strip is automatically fed toward the work, which consists in malntaining stable the resistance 10 of the welding circuit external to the arc and in utilizing changes ina characteristic of the arc to maintain the are.

In testimony whereof I have hereunto signed my name in the presence of two subscribing witnesses. I

HARRY n. MORTON.

Witnesses: a

'ADELE S. EBEBHARDT, DANN L. W001).

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