BE635724A - - Google Patents

Description

       

   <Desc / Clms Page number 1>
 



  "Improvements to aros"
Many properties of arcs or electric discharge. do not vary linearly with the magnitude of the arc current, but on the contrary they appear or are noticeable only when this magnitude exceeds a certain value. The present invention relates to a method and equipment for causing such properties or bring them into play when it is impossible, difficult or undesirable to maintain the magnitude of the arc current above the indicated value or, otherwise, to achieve control of the arc current. ownership where possible,

   useful and desirable to maintain the magnitude of the arc current above said value,

 <Desc / Clms Page number 2>

 
 EMI2.1
 A prime example of such properties is the property that an a: king possesses during an A 1 welding process! arch appealing to a.

   electrode concommablop to cause a transfer to the welded part of the molten eleotrode material all in the form of a sprayed transfer called projected small droplets which provide a deposit and establish a good weld * This property disappears when the importance current falls
 EMI2.2
 we disapprove of a particular thief, park * that at this moment,

   the Xitu to transfer the molten material forms a spray which is projected by the arc as a rapid stream of small * droplets traveling under conditions of free flight or practi-
 EMI2.3
 After free flight from the consumable electrode to the part, the molten electrode am "tiara forms a large globule before any significant transfer takes place,

     a series of these large globules forming a coarse deposit and consequently tending
 EMI2.4
 give a bad weld * this is not the only drawback $ however, since the transfer itself is not affected by the arc (since the arc contributes practically nothing to the transfer mechanism), it is caused either by the
 EMI2.5
 gravity, or by the fact that the global and the part meet.

   In either cage, the part is placed below the consumable Itelootrode and this constitutes a restriction India * sirablw at certain times * lg * n will only account for the value of the current of the ara above which satisfactory welds are obtained and below which non-satin welds are obtained is not a single precise value, since there is a wide range of current values producing welds of medium quality.



   A particular example of a welding process exhibiting the aforementioned phenomena is that of using a consumable aluminum electrode with a diameter of 1/16 inch wrapped in argon and using a current arc.

 <Desc / Clms Page number 3>

 continued.

   Good weld is obtained for currents above 150 amps and relatively good welds are obtained up to about 140 amps (the rate of electrode delivery being reduced accordingly).

  . Below this and with a feed rate of about 120 inches per minute we discover a discontinuity in which a new relation exists between the current and the consumption rate of the consumable electrode and for which the current changes from about 140 to 100 amps, This transition is accompanied by an approximately ten-fold drop in transfer frequency and hence a corresponding increase in transfer size,

   the transfer below the discontinuity (the so-called range below the threshold) taking place in the form of relatively large globules reaching up to 1/4. inch in diameter, which is equivalent to approximately 2 inches of the length of the aluminum electrode. Some improvement can be obtained by reducing! Depending on the diameter of the electrode, but this requires an increase in the feed rate of the electrode for any given current.



   Due to the fact that hitherto high currents have been maintained above the level of discontinuity to achieve the spray transfer, it has not been possible to satisfactorily weld thin materials. Another disadvantage of the prior methods for the satisfactory welding of thick materials is that, even above the discontinuity, the transfer of the projected spray does not always lead to constant results, nor is any given weld as regular as it is. 'it would be desirable.



   The first example of an arc property given above is the establishment of a spray transfer. A second example resides in cutting. The cutting of a part 'can be executed only when the amplitude of the current is greater than a certain value, because below this value:

 <Desc / Clms Page number 4>

      the material which is founded by the aro remains in position on the pieoe
 EMI4.1
 where it does not solidify on cooling, while above this value the molten material is driven from the part.



   The basic principle of the present invention lies in
 EMI4.2
 'O;: tj that the arc: must It1'8 m11S operate cyclically with at least two iv6aU% d1ftérnts returning cyclically, an expression which will be further detailed below. Equipment for electric aro <? following linvmhtion includes a power supply system 86b. <: - .. el "rtt" 1cu] ;. Where the supply of an electric power t electrodes (which in the case of the aforementioned welding operation (,; .. u:

  'constituted by the consumable electrode and by the part, ras- peo't5, v.ern,) llt). eyetime comprising a '180-1' t puiosanoe oouroe, r.q5 intended to supply a powerful electric power to the electrodes and comprising means which either have an impedance determining the power supplied to the electrodes, or have a second source of electric power intended to provide a
 EMI4.3
 electric power to the 'leotrode8, the means being provided * to act, in a way other than we control the aro, a
 EMI4.4
 cyclically to cause the arc to work at at least two different levels returning oyolically.



   The two aforementioned levels will be called, for convenience, the lower or substantive level and the upper or increased level. When the equipment is fully dc working equipment, the increased level is simply a dc level higher than the dc background level and no further explanation of this term is needed.



  However, when the equipment is totally or partially alternating current equipment, providing the liver with background and increased currents which already fluctuate oyolically or rhythmically, then operation at more than one level implies, for the increased level , that the amplitude of the harmonic component
 EMI4.5
 principal of this nivduoz (c'c:; 'i.-4: .- say the amplitude of the maximum instantaneous value of this component whatever the sign)

 <Desc / Clms Page number 5>

 
 EMI5.1
 oci 4 ", jl" 'ltU1X' h the amplitude of the component haJ'80Diqu .. princfpa- 1 & '". \' ÓQv. due background.

   For the department. who work in puviî * .-. alternating current and partly direct current and which ii '.- atftiysMnt an arc with an alternating current comprising a * Qw & -t-.i. \ it * of direct current, the increased level is the amplitude of the ccir h jS) , nttantane when the alternating current has its value of 01- .. let ttgme polarity that the component of direct current, tunJl "qua the level, of bottom or base is the amplitude of the current ïnei ##: U loraqt19 the alternating current has the peak value and the polarity opposite to that of the current component * con-bitm.



  Ku making the two-level monk work the arc h, he dvi "dh pOt, s1bl. To reveal a perceptible property of- aro or zeu p.tSaon06 by leading him to play effectively, ilLli, -4 1 '.1 :: n'tI, U'111' the magnitude of the arc current above the area so far as necessary, also lon-, <i,.; ##. The level at * ru 4 and greater than this value, - while
 EMI5.2
 1 \ <<u. u <ions 1, H} I4't 8 be 1n! 'r1eur lx this value. A 400% 101'111
 EMI5.3
 \ "1 ,, ;; \ 't." ...' HI! possible. since we can provide d44, ') y'h'u.n: tfl f4v, lower vt.nS. A second advantage is that lt ap-; p11. (. I &, UQn of the increased level allows a command of the = ment where the pro- 11i: ';. 6 .r'pIi.: Rt1.tt or water Sir his presence .

   Indeed p this second 6, '' '' l '\ .., t they r, (j, n,: 5f \ U. Eauti the first, if we deny it because the h- "'"! <Lncl} ( Ht1i hearth maintained above the aforementioned value '"$, 1; t'Il,) Rcoru then simply commands the moment to appear, h. The property 1ntô1" $ saa.nte.



  The two aforementioned advantages are of particular importance; ;; for arc welding with a consumable electrode.



  Thus, firstly # the minimum operating current 'rmut ,, e4ou-kk, ie the background level, can be lowered well by *, 1 {iriii of the average current corresponding to the consumption speed.', ; 3n / .t for the desired electrode supply vi tau "8, q) 1. :: t> 'in..I'é.rii1ur at the normal discontinuity level, while

 <Desc / Clms Page number 6>

 the increased level is greater than this average current and the level of discontinuity *, such that the background level simply tends to melt the material of the electrode slowly to produce a large cell,

   But the increased level acts so as to effect a spray transfer of the molten material as small droplets before the material is able to fall under the effect of gravity. - that the increased level may contribute to a certain extent to the melting and just as the background level may contribute to a certain extent to the transfer under particular circumstances, but essentially the aim is that the merger should be caused almost entirely by the background level and that the transfer is effected practically completely by the increased level.

   The frequency of the transfer is thus directly related to the frequency of occurrence of the increased levels, while the average value of the material transferred is determined by this frequency and the rate of consumption. This reduces the average current or power required for the weld, so that the weld can then be performed using a wider range of currents and power values than before. and the power required allows the welding of thinner materials than has been possible heretofore and reduces electrode delivery rates and travel speeds.



  So, for example, the average level (i.e. the average at the liver of the increased and background levels) can be as low as 100 amps for aluminum electrodes with a diameter of 1/16 of an inch. or even as low as 50 amps for this size and even less for thinner electrodes, the increased level required for the transfer obviously being much higher both than this average level and the background level.



   Second, by making the increased levels responsible * for the transfer of material from the electrode, a greater degree of

 <Desc / Clms Page number 7>

 control of the transfer is possible than previously and a smooth and frequent transfer becomes practically possible without difficulty, applying the increased level cyclically and frequently. This particular advantage can, if desired, be obtained even when the background level is higher than the level of discontinuity, conditions under which the transfer of the projected spray would occur even in the absence of the increased level, but not necessarily so regularly. or as frequently as desired.

   For example, with a direct current above the discontinuity level, the transfer can occur at a relatively low speed well below 50 times per second, but it can be achieved 50 times per second by using the power distribution network to provide an increased level of this frequency.



   Whether or not the background level is greater than the discontinuity level, the transfer is achieved primarily through the increased level. The background level maintains an arc between the consumable electrode and the part and; ...: melts the electrode, whereas the increased level returning cyolically transfers the molten material to the part which is being welded * :

     
An arc welding system operating in this way can be such that it operates with a so-called self-regulated arc, i.e. a feed mechanism is provided for the electricity. A consumable trode so as to supply the latter to the workpiece at a preset or normally constant speed, the electrode being consumed by the action of the arc so as to maintain a substantially constant arc length.

   Alternatively, however, the feed mechanism can be controlled by the voltage of the arc, through a servo-mechanism, for example, so that an increase in the average arc voltage above the equilibrium value causes an increase in the average electrode feed rate in order to re-establish equilibrium, as in automatic arc welding 'or ordered.

   In addition, the elotode may have a thin re-

 <Desc / Clms Page number 8>

 coating garment with or without an additional gas shield, where flux can be added, or the electrode can be coated with a thicker flux coating in a manner analogous to arc electrodes metal for manual work.

   The invention finds particular utility for reducing edge and speed of consumption in soldering operations where the normal current density in the consumer electrode is very high, for example 50,000 amps per square inch and / or. or the consumption rate of the electrode is normally greater than 100 inches per minute.



   Equipment according to the invention can, however, be used * Without other sticks, for example for cutting, lighting or heating, when it is desired to obtain a certain property of the macaw maintain the single level arc current needed to make the property appear of interest * By working the aro at two or more levels, one can in fact obtain a mixture of arc properties normally associated with the different levels.

   With the equipment for the above uses, neither of the two electrodes should be consumable and the arc can work in a neutral gaseous atmosphere or not, for example in air, at atmospheric pressure or not. The invention can be used for cutting work, where the background level causes melting and the increased level drives molten material from the workpiece, which is thereby cut.



   Many different programs for an operating cycle are possible. For example, the background level may be a simple sinusoidal current waveform acting during only part of the system oyolus, while the increased level may be another simple sinusoidal current waveform having of a higher amplitude and only acting during the rest of the cycle.

   In a second example, the background level is again a simple sinusoidal current waveform but in this case this waveform is applied during the in-

 <Desc / Clms Page number 9>

 
 EMI9.1
 third of the oyole, while bulb. tm or more otoatente of oe., 01e'l the increased level is applied as h form, for example, 4 'i8p \ 11- niona whose amplitude is greater than that of the background level and which are applied less than one times for each half cycle of the. waveform, more than once or exactly once. In- ;
 EMI9.2
 Corn 1.! \ X1S Another example, the background level is a direct current level and the increased level is an alternating current which is applied purely intermittently and oyo11ql.letl1ent.

   Still in another oxea 1e, the background level is a direct current level which is applied intermittently and oyolically.



   The aro current in any cycle can have a pattern consisting of one or more background levels cons- or
 EMI9.3
 tanta / in direct current and one or more constant increased levels or in direct current, with a rapid transition between the levels, which provides a rectangular waveform, which may although not necessarily have certain distortions by
 EMI9.4
 : 70'.I; .... 't'u: i oon av4la a purely rectangular wave forae s4om'tr1- tn3 ilitb 1 \ tl ra possibility is that the level of: tond h ,: ". . I .: direct current level, while the increased level is given by a triangular shaped waveform superimposed on the top of the direct current level, this form of inducing growth or fall. either fast * or relative holds len, eae with or without a relatively flat top.

   Instead of the tnangular wave foras, a single half cycle of an ft1nu'Qtd wave on $ avoc or without a flattened top, can be sl1perpow 'at aoamet of the current level atnt9.ru.



  The equipment according to the present invention should not be confused with equipment having auxiliary devices.
 EMI9.5
 11a1re to stabilize or re-strike the arc. Such auxiliary devices are of two different types. The first type provides high frequency, high voltage spark injection.
 EMI9.6
 i!). li.me the gap between electrodes, but the li-mGma device does not supply power to the electrodes but acts as a

 <Desc / Clms Page number 10>

 so as to exile the interval of such aorta that the power
 EMI10.1
 denies to el otrod * 9 by another foroe of electric power can Qrêw or maintain an arc.

   The second volume of auxiliary device provides unidirectional peak injection as
 EMI10.2
 described in the patent; in Great Britain No. 705,164. This orgte injection device is connected to the power supply of the electrodes. The device also acts cyclically, but it does so entirely under the control of the arc, serving
 EMI10.3
 to provide an extremely short magnitude for each alternating half cycle of the aro's alternating voltage, in order to maintain the arc and to prevent the rectifying characteristics of the arc from coming into play.

   This can be contrasted with the equipment according to the present invention in which the aforementioned means act independently of the arc and, therefore, the different levels returning oyolically do not have to be repeated at the same rate as the current. alternative of the arc itself
 EMI10.4
 m8ma.

   In addition, it can be said in general that while the removal of the peak injection device from the prior equipment would cause the arc to go out, either immediately or after a few
 EMI10.5
 cycles, removing the increased level will not cause the aro to turn off, as it can be maintained only by the
 EMI10.6
 background level, although, as indicated above, such an arc may not be particularly effective for any particular purpose, for example in effecting the transfer of spray.
 EMI10.7
 projected risation.

   Another difference to the S te gold injection tools is that the latter offer. as one 8uramp11tud indicated. or an extremely short peak, while the means of the equipment according to the invention have preferably been provided to act in a cyclical fashion such that the increased level serves.
 EMI10.8
 maintained for a substantial period of time, on the order of one wave or more. The increased level can be repeated in any desired way, for example. $ tro applied from 5 to 500 times per second.

   The frequency shimmers can by

 <Desc / Clms Page number 11>

 example be a simple multiple or a sub-multiple of the frequency of the power supply network, the latter constituting the first source of electric power intended to apply the background level, while the increased level is applied either several times per year. in each cycle of the distribution network, so that the cycle of this distribution network and that of the system are the same or, in another way,

   the increased level may be applied to only one liver for several cycles of the distribution network * such that these cycles constitute one cycle of the system *
Another characteristic which is different from normal peak injection devices is that the average of the increased level is appreciable and, in general, is greater than 5% of the average current of the background level. (for alternating current arcs, the average values indicated are the average rectified values).



   The increased current controls the transfer of material from the electrode, as described above, but it is necessary for a general ratio between the powers, the current and the mean voltage; ne, to satisfy the equilibrium requirements with the consumable electrode. Thus, if the electrode is supplied at a preset constant speed, then the power source should be substantially of the constant potential type, such that arc variations in arc length (which is equivalent to variations in arc resistance) and the result is compensation for variations in the average current.

   Alternatively, if the power supply has a significantly higher RMS open circuit voltage compared to the arc voltage, the power is approaching! then of the constant current type (albeit with a pulse waveform) and the supply to the electrode should be adjusted to match the rate of consumption. This latter adjustment is usually achieved by a simple servo-system taking the arc voltage as the basis (which indicates the length of the arc).



   As indicated above, the means intended to modify.

 <Desc / Clms Page number 12>

 
 EMI12.1
 The arc current in electric arc equipment can either include a second source of electric power intended to supply electric power to the electrodes, or have an impedance which determines the power supplied to the electrodes. 'one and the other case, the oyoli-
 EMI12.2
 that can come either from a switching device acting cy.



  Ql1ment (which can be a mechanical switching device 16 \ 0'0 xÉ 4a.ai w ', v & X1 / * therralo! 11cu8 or semi-conductor, by &:,! #. .LA iItpoe.1 t.tt da orutation k tranSi.tol'a), that is to say of the na- 1 '! t.). own dee means oux-manea. For example, these means may take the form of a second power source which is ut; o alternating or pulsed source of pll108W1oe, or in-! wv * 1 * lee aoyena p.v8nt present the lmp6danoe or the form of a rectifier or redrenaour network which acts cyclically by letting the current flow in one direction and not in the other.
 EMI12.3
 be.

   Other details and features of the ressua invention are taken from the description oi-apraa, given by way of non-binding example and with reference to the accompanying drawings, in which:
 EMI12.4
 Figure 1 shows an arc welding system carrying a single source of AC or DC power.
 EMI12.5
 



  Figure 2 shows an arc noudare system similar to that of Figure 1, in which the power source supplies alternating current to parallel circuits through the in-
 EMI12.6
 via a two-wave rectifier bridge and a half-wave reducer, respectively.



   FIG. 3 shows an arc welding system comprising two alternating current or direct current power sources, connected in parallel with the electrodes of the arc.



   Figure 4 shows a system similar to that of Figure 1, in which the secondary winding of our transformer

 <Desc / Clms Page number 13>

 
 EMI13.1
 OMt1t. the second of the two power sources * Figure 5 represents a system analogous to that of flowers 3 and 4, in which the ill.p4danott in the parallel circuit for the varying arc current oyo11qu.nt do not deny the indaîras Lit figure 6 represents an arc welding system xt0- * dit'1. comprising a capacitor constituting the second source of
 EMI13.2
 powerful.



   FIG. 7 shows another system comprising two power sources available therein.



   FIG. 8 represents a system constituting one aspect of the present invention and comprising three power sources in order to make the arc work at three different levels.
 EMI13.3
 cyaliquatMnt.



   FIG. 9 represents a system similar to that of FIG. 7, but particularly suitable for operation with a controlled arc and a consumable electrode.



   Figure 10 shows a variant of the system of the
 EMI13.4
 U.ic: - "9 including means for controlling the power supply of: 1 \:, M '' 'i,') 1 ihdJ: H> iI1tu.abl. According to the increased current level.



  The fig it represents a system similar to that of, 1; ttgl1r. 3rd gyeo a starter circuit.



  Lou fleuiea 12 and 13 represent from $ system * modified \ .t cni IL) i'8fir "* us Ui * s ooanandéa to silicon.



  Figure 14 shows the system in the IMS "". UOl \., Olyphilised feed. is the second power source *
 EMI13.5
 2acs lo Y8tèm $ with arc represented in figure 1, a <besides 4 * single power Pl is oonn <otët <n series with an i8pédaD- ce The power source and the impedance being connected to the two electrodes 1 and 2 which , when the equipment is to be used
 EMI13.6
 e for arc welding, a present in the form of an ilte-
 EMI13.7
 consumable wire trode and workpiece, respectively.

   Zn payllèla with impedance Z1 is connected to a second impedance 442 M't wérife with a switching device 0 which introduces oy-

 <Desc / Clms Page number 14>

 Click the impedance Z2 in the circuit in order to reduce the total impedance offered to the current through the arc and consequently to increase the level at which the arc works.

   In this example, wire 1 is 1/16 inch diameter aluminum wire which is fed at a rate of 100 inches per minute. The low current level is of the order of .µ0 amperes, while the current level increases this by the order of 200 amperes and is maintained weighing approximately 8 millisscondes with each operation of the switching device C, the cycle being repeated at about 50 times per second.



   The dotted line 3 in FIG. 1 is intended to indicate that in an arc welding system comprising a consumable electrode 1, the latter can be used either so as to provide an automatic arc. -regulated with a pre-set electrode advance speed, i.e. a so-called controlled arc, with which the electrode supply speed is a variable which is determined by a servomotor sensitive to the voltage of the bow. In the latter case, a nearly constant current supply at each level is desirable,

   so that the operating currents are not strongly affected by variations in the voltage of the arc or the length of the arc. This is easily obtained by providing that the open circuit voltage or the voltage effioaoe in open circuit of the power supply P1 is clearly higher than the arc voltage,

   for example equal to three times the voltage of the arc or greater than 50 volts at this voltage * The rms open circuit voltage of the power source P1 is defined as being the voltage zone given by a straight line passing through the voltage-current working point having the same slope as the output characteristic of the power source P1 at this point.

     Alternatively, for operation with a self-regulated arc, it is desirable that the open-circuit voltage or the open-circuit rms voltage of the power source P1 be reduced and not be much higher. to that of the arc, as defined in the patents in

 <Desc / Clms Page number 15>

      
Great Britain No. 767.688 and 767.689. This condition applies mainly to the current period aooru, in which, for good self-tuning, the total impedance of the circuit must be low compared to the arc, so that the latter is the factor. dominant in the control of the current of the circuit.

   Thus one method of operation is to use a nearly constant potential power source with negligible limiting impedance (i.e. Z1 and Z2 providing low total impedance) for the increased current period, in order to d '' provide means for self-tuning and for increasing the impedance of the circuit (when Z2 is isolated by the switching device) to provide the low current period or background during which, given that the consumption speed is also reduced, rapid self-adjustment is less important
In the example just given,

   the power source P1 can be a direct current source and the impedences can then be mainly resistive, although for improvement. In order to maintain arc stability, some circuit impedance can be usefully added, especially when the open circuit voltage is low. Alternatively, however, the power source P can be an alternating current source, in which case the impedances are usually mainly reactivated. In this case, it is useful for the switching device C to cut the current. in impedance Z2 in the vicinity of zero current or at the time thereof.

   The switching device C can be a mechanical device with one or more breaks in series, or it can be an electrical or electronic device such as a vacuum contactor, a controlled gas discharge device or a semiconductor, depending on the requirements of particular applications.

   The switching device C can operate at a single multiple or a submultiple of the frequency of the power source P1 or it can be operated at or near this frequency, like this se-

 <Desc / Clms Page number 16>

 This would be the case when the switching device presents itself to us in the form of a rotary mechanical switch driven by an induction motor supplied by the power source,
Again, in order to promote the stability of the arc and
 EMI16.1
 in particular the re-priming with a 1-teratit current supply, of the well-known auxiliary devices, intended for the injection of high frequency and high etinoella 1;

  en- i, a. one ridge injection as deor1t in the patent in tea. à * Bj <ietftgn 8o '3. i 64, can draw incorporated according to the papticulihrea requirements of the consumable electrode arc which have m;> 1! 1 & 1'1. * As an alternative to the arrangement, shown in i. # ±, .. <'., <1 $ a 1mp6dan <) 6 can draw C01U1.ct in parallel with the prâulre oeuros of power across the electrodes and a say. positive switching working oyolically is connected in other way with the impedance or. in parallel with a part of it, in order to increase the current cyclically.



   In the system shown in FIG. 2, the first power source P1 is an AC power wall and is connected to the first electrode 1 by a rectifier 4 constituting means offering an impedance. A double rectifier network in bridge 5 constitutes medium seoonds offering an impedance
 EMI16.2
 dance and it is supplied from the first power source P1 and is connected so as to supply a rectified current to the electrodes 1 and 2. The alternating current source P1 can be constituted, for example, by the winding secondary of a transformer with one end connected by the rectifier 4 and an impedance Z2 to the first electrode 1.

   The other end of the winding can be connected to the work, not directly but through one of the four rectifiers of the double bridge rectifier network 5. With such an arrangement, the arc is offered to users. alternating cycles with pulses which, by making Z2 low enough, can be at a high or increased level

 <Desc / Clms Page number 17>

 
 EMI17.1
 The arable bridge rectifier network offers an output signal at each half cycle of the source in alternating OOI11'a11t, the rectified OQ.ttL $ signal being applied * to the arc by means of an iarpédanoa 31 which can be returned sufficiently large so that the current resulting in the aro constittie its background level.

   The ro4rouuour 4 in series with the impedance Z2 acts in an oyol way as a conductor dVMaJ1t only at half a cycle out of two and this is to ensure that the arc works cyclically at two levels.
 EMI17.2
 FIG. 3 represents a system according to the invention
 EMI17.3
 comprising a second power source P 2 which is provided for! working in an oyolîque fashion using a 008muta- device; !: oyolic ion C intended to oonneot the second source of then8an-1 G4 to oo trodoa 1 and 2 and to disconnect it, so # .lut 1 ;; ... 1'C alternately supplied by the two sources and pak la) rot1Hu. "Souroe only. Each power source can. 'H' b0j [/ 'na" direct current or alternating current or 1' ;; ,,, JIJH, Í ') Qfl nu df.1 <Â, and all of them can be oonneat48, .i.

   W * \, tl.a. ijropxc Íln.r "1, noe Z and Z2 'respectively and a 1'! Ù..L, t ',, \}, Ó:,; (H1tJotWlablG 1. As indicated by the dotted line *, jt eettt) 61cetrode can be advanced so as to establish an arc s.¯.> K 'c un ,, \ 1: 0 self-tuned Q!' II.1JUiI indicated pr4c'demmont, and des ') J' r, r.t '' f..c may be intended to stabilize or revive-, Y, .- the ai'o nor this is considered desirable. Useful values .t "; ' 1. 41cnta of circuit of the system of figure 3 when 18 u.xSki ant .J)! '. TVI, l POIl ;;: - self-adjusting rJtr6 consist in using as 2rQ1ôre power source P a source of 35 volta in current O (nt1lJll and for the first impedance Bzz a value of 0.3 chou in order to provide a background current of up to 30 amps.

   The second 1 .t: i) u, r., Of power P2 can then have an output of 35 volte ra.; Ai..t alternating and the second impedance 25g a value of C'j, 1 ohi d'ln of give an increased arc current of about 200 ampb; #### h .. r4) I, n "controlled operation, the output voltages of

 <Desc / Clms Page number 18>

 
 EMI18.1
 the first and second power sources P1 and 72 POttr "would be increased to about 100 volta in direct current and alternating current, respectively, and the values of 18 feet.

   these be also increased,
The first power source must / not be connected.
 EMI18.2
 nocturnal permanently at the two electrodes as in the example which has just been described, because as an alternative the switching device working oyal, quarent can be provided to connect the two power sources in sequence to the electrode , so that only one source feeds the aro at any given time.



   In another example of the system according to the invention, represented in FIG. 4, a second winding of a transformer constituting a second power source P2 is connected in parallel with the first power source P1, at the terminals of the electrodes 1 and 2 and it works oyclique because it cons.
 EMI18.3
 titutes an alternating power source or 1apul.ionntlle.

   The first power source P1 1 is a direct current source
 EMI18.4
 noted by an impedance Z1 at the electrodes *, the impedance 21 being constituted by a control resistance and a stabilization reactance. This first power source P1 offers the background constant, while the increased current is offered by a AC current P 2 connected by a rectifier 4 and an impedanos Z2 to the terminals of electrodes 1 and 2, in parallel with the first source P and its impedance Z1.

   With such an arrangement, a current flows from winding P1 only when the alternating electromotive force becomes greater than that of the arc voltage and this occurs at the frequency of the power applied to the primary winding. . For cyclic repetition at
 EMI18.5
 double this frequency, a two-wave or bridge redoresor system can be used, and for a multiple of this frequency, a series switching device with the rectifier can be used.

   This offers the advantage that the switching device can be designed to open only.

 <Desc / Clms Page number 19>

 
 EMI19.1
 in the tbwMOw of an olest load i.e. after Iw wM9a '<) at 44 stopped by the action of redransemmtt Du = * & ut way * m 4i p - aitit ooaumdd rectifier such as an ooawukâé rectifier 111- where may be useful and diolaaohi of the appropriate fffla * in place of such a combination 4 * a device of osMmtwtl ** #t * # a redranstar * For M fonotioanemoat d laro auto- 41SIde 1 * elder ,,. fired with a rsdrssstur should have <UM âa1 ', s top4dim and the order of the electroaotriot force l.taornn.r dolt r aM'; - risurs of ur.qur volts only 1 * t may have 1 '4ma ma current of bottom of the notroo proxy.

   D '<UMt nut twOM4 any-
 EMI19.2
 faith, for .. '\. 11'81 "a oon.r6, s more preoim 4 * ...... #aamM 1 you can \ .1t111.er an electromotive force a1'r.Dat1T' p188 él # v # # * a 1mp'dano. of t3tlttliBtlt, l1 who can Itr. prtAcd, .- 1 r.6: ttJA'tt. ".. and we want it, ltéleotrod. oon80 # aable p8 \ .lt - $ 'tr <! # m; motion in. as long as 8, yatèlli 'iL arc e $ MMM9.d <.



  With the 81.t .. vaaant 4i * itr * 4éed.'t. J.a 4Uur * 4 \ $ 1 00 .. rant acoru fit 1nté1.u.r. k lU1 4ea1-cycle, cNt 41tan1t 3 <& r <M.SM?i <) i rely probable when the orl. da 3m t4 \ 'N4 rr, re' 8.ul.llen1i. Arin d to hold 1 * éhu ',,, d. ! '# * # to .-' i 1l1- 'eeulament. In order to obtain A duration d <oeurejat aOfttr-U jp2iua "ajamgnegr que oeoi and 8upér1. \. 1r .. t1 ru doaī <5ycl .. Seaa., Szur, alternative can 8be prepol xi * e pax one yes - 4 <0s E3 tstt> aiw! J tina eupplrfaantaire 4rie dno * ow * # 3! ' TRBsapM "t 1 tinu 8upplla.nta1re a4r1e .... aro that the first '0111'0' of coarMit ..... 'Ori'! M nworcoaSSbe: 80 \ 11'01 of direct current can ta1: N party * ilai La jw atâ & z> 4Wu.rr.08 of direct current or. 4 be combined * - "'" .ar ...



  Dan. oette "arīte, px.T ..w .... ūoe. &. un. 8011ro. e.ltlmat1'Y ', from such: l .. prwatièrw ll" .. u. 8ur -UA an alternative aouroe, such <Mf j îfaws KaqgwrtL'a & a aur alternative background level with a 111 ...... 1t aoorui period 41q \ t ... At when the second * 8oU ". Mal1: 1beftaU..1.: ... nltt -. "9n.ao-.
 EMI19.3
 is holding
 EMI19.4
 The 1mpéd.no ...- m.'t1oaa'- 1 ** exeopl- * préoéïl * * must not. 8tre des 11BHSdano .. l1JJ6r .. 1D.18 <ï3Le}) 8lrvwtt;

   

 <Desc / Clms Page number 20>

 
 EMI20.1
 Present to you under the fora * of nonlinear device, such * as saturating iron core inductors or resistor with variable voltage-current characteristic and such devices. tifs can be particularly useful to accentuate the level
 EMI20.2
 increased currentq For example # in a system According to the invention iiin r.pr68ftnt the flower * 59 a first 80u.roe this power,? 1 and a first impedance zi 1 are arranged in series at the terminals of the alotrod '8 * while in parallel with oelles-oi are dlipo * ét # on * orle the tm with the other, a second source of pay *% ea, .a: alternative p 20 a rectifier 4 and a non ispedanoe l1n4 & 1- # *% Z2 (for example a known lmpedanoe oocueroîalomont v4 *% UâtO'11).

   Coati leads to a * some saving of then.



  It! U1.S and at a more pronounced 01 "tl in the period of increased current than with the analogous equipment previously described and having linear impedance.



     In yet another system according to the invention and shown in FIG. 6, a first power source P11 and a
 EMI20.3
 impedance t 1 are connected% in series to the terminals of electrodes 1 and 2, as previously connected to the limited electrodes have also connected a second power source P2 not having or the form of a capacitor connected to electrodes 1 and 2 by a device of oOllml. \ tat10n C and an impedance Z2 # the non-denser P 2 is charged through another impedance z3 h a separate DC source P21 and the increased level can be established at any desired rate,

   by operating the switching device C and thus discharging the capacitor in the circuit comprising the electrodes 1 and 2.



   When two power sources are provided, they do not necessarily have to be connected in parallel with one another and at the terminals of the electrodes, as shown in Figures 3 to 6.

   FIG. 7 shows a system according to the invention in which the second power source P2 is in series with the first power source P1 and the electrics.

 <Desc / Clms Page number 21>

 
 EMI21.1
 from 1 and 2 seat arranged * so as to work 7011qu ... n't 11 "& - 06 the fact that we have an alternative power source
 EMI21.2
 
 EMI21.3
 or 1mpu.la1onnel16. the first new one .- Ce of power P <can be;

   a direct current supply or an alternative current source
 EMI21.4
 If desired, the bow can work more than two
 EMI21.5
 x9.veo.t, different revommt oyoliqu.ement, case in which one pure '. sees an oyclically additional working circuit which is intended to act, other than the aro control, in order to bring the arc to work at different levels * shark. For example, data the a8tà # .e represented in figure 8, a first end of the pu1soùac P. and an impedance Z. in series with where it is.
 EMI21.6
 cor.noL6a to the elootrodon bernas in order to offer the level. background or do baat.

   At the terminals of the electrodes and in parallel with the l) The fl1it; the & 001lrot of power Pl and its impedance Z. have 4'- onneoté1 on 861'1e one nveo the other, a second Impedance 5 Z2 # a r.e1rCUJu6Ur 4 and a secondary winding of a tran.torma- taui5 ctti-tujr i * a source of] power P 2.

   At the terminals di? ïj otrcd "s.uT. :: 'r;:; nt f'c: on6otée. in pmxallèlt with the dsux ri'tvs l-Uijnfc & U!> ua on one with" The other @ a three- Kis .9! iî.'pt 'iUui-; s a switching d18p08i tif C and a Gond in ...... tettr! "' 1 'c last dtsi ohnrgé through a iap4danol nuppllê- Rtantî ..- 3j cal s souf-- # CI (} haix Pj 1. oondaneatour P3 can '! "# Nr T-' '' 1 !! l ''} îa; the tH.-; '.., .te duration and high energy, which can be rea 1 \ BIlt "'V' '\') ll.l.1" either during the period of sharp current M !, running from the.qu.J:; "'& the second source of power P2 agitates either ta pùrltC 1 '? * arc tr'1 "fs.1l1t a / .1 background level.

   This,
 EMI21.7
 The osposite arrangement can be used, for example, when the concentration of ni goes to a bottom and the increased level due to the aourco wave of power leads to the formation of a non-venable drop at the pointa of the consumable eleotrode, the taoheaent of the gouttolatta being completed by means of the discharge of the oondenaa- tOlU 'TIR1n ertpn8 4quipemo.nte according to the invention, the..0- 1n provided to fRire cyolically vary the current of the bow

 <Desc / Clms Page number 22>

 can be considered as a second power source or as an impedance.

   Thus, in one form of equipment, a power source P can be provided with two separate sampling points in order to offer two different base levels. The power source can, for example, be the secondary winding of a transformer having different intermediate pry points. This can be viewed either as a single power source with different sampling tips, or as two power sources having some parts in common and providing an arrangement similar to that of Figure 7.



  One sampling point can be connected directly to the consumable electrode by an impedance Z1, while the other eet connected to the same electrode by an impedance Z2 and a switching device in series. The sampling point connected to the electrode by the Z2 impedance offers the high level. This level can be produced by choosing a prie point on the coil * 'whose electromotive force * is less than that of the point
1 'conneoté to the impedance Z1 impedance Z2 then being much smaller than the impedance Z1).

   Alternatively and as shown in figure 9. the high level can be produced by establishing * a circuit for a second impedance Z2 and a switching device 0 from a sampling point whose force The electric motor is greater than that of the point connected to impedance 21. The first variant of figure 7 is more suitable for self-regulated arc operation, while the latter variant of figure 9 is more suitable for / operation with a controlled arc.

   It should be noted that with this latter type of operation, although the electrode feed mechanism is normally based on the mean axis voltage, it may be preferable to use the voltage of the electrode. arc Average taken in a part of the sequence of currents, in particular the period with increased current level, at the coars of which the consumption of the electrode is higher.

   A suitable system to obtain c

 <Desc / Clms Page number 23>

 The result is shown in the fiacre 10 for a direct current are, in which case on the input side of a disoruimator 10 the resistance and capacitance combination shown at 11 has a time constant of the order of. 1 millisecond friend offers, thanks to the rectifier 12, a longer discharge time constant.

     These time constants allow the capacitor to charge near the peak of the arc voltage during a period of increased current while being immune to parasitic voltage surges such as those which occur at times of transfer. The rest of the system comprising the controlled voltage supply 13 for the drive motor 14 of the electrode advancing rollers is in accordance with common practice.



   As a further example of operation with a self-regulating ato, numerical values will now be given for the elements of the circuit of FIG. 4 suitable for this mode of operation.

   The first power source P1 is a direct current source (battery, dynamo, single-phase or three-phase rectifier transformer) having an output of 25 to 35 volts in open circuit, the first impedance Z1 1 being a resistor intended to limit the current of basis at an order of magnitude of
10 to 50 amps with, if desired, a reactance of the order of 0.2 mH,

   in order to help stabilize the arc and reduce the bypass of the pulse current in the source P1 (this consideration is not important in the case of power supplies with rectifiers), the second power source P2 is an alternating current source with an output of about 25 to 35 volta in circuit or. green and with a diode rectifier at.

   silicon 4 in series with it and the second impedance Z2 is a resistor of sufficiently low value and negligible reaotanoe to allow pulse currents of the order of 100 to 300 peak amperes
This system is suitable for pulse transfer control for 1/16 inch diameter aluminum wire in argon with consumption rates on the order of 100 inches per minute.

   For consumption speeds

 <Desc / Clms Page number 24>

 
 EMI24.1
 lower than * very "" 'J1 4 # itapuléieis lower * than 04l11N of the distribution network penvaat 4 be used, without calling for example a simple rotary switch to cut off the unwanted pulses or by replacing the rectification preferably by a silicon controlled rectifier, which can be deolea- \ .10.f; there will * v J.1 '' 4A ton) t1onneme: n1; with an are command, in which i.'6w-s owed the elessoda $ t as a function of the arc voltage or 1?! ' GSIlJ d, ''.:. Fi.1t ", '! 4t \. $.', 4 'manual as for welding at 61¯0- 9rQdt & barii, isa 48tér1et1q.8 total. De la aouroa dt pays * -! khThese must not approach constant current (royantj.

   In this h'Alt 4eo tensiosafi efficient in open oirouit high piM / and '4 {, * # / - # |>? U6 llt \; cJ)' ', 1, Ut & 8 are noe8s..ir'8. So in liexulm.



  1 sî avtUÀ4} the LfT: lona are increased to about 50 to 75 volte for Pl and F2 (which can be one and the same Douros) with the appropriate circuit impedances to limit the currents to the levels defined below. -before.



  There is a practical point that $ # applies to all
 EMI24.2
 systems described, about starting the. process. Although
 EMI24.3
 high teasien sparks (high frequency bloeu) could / be used to ignite 1 ewro, otc1 offers 41- towards disadvantages including r..1ttào.1q interference ...



  Normally, for high currents, the praatl is started allowing the electro4e to hit the, 1 .., r .. 1 the 0 '"rant of the circuit breaker (in particular remove the or @ from power sources to * flat characteristic "and at all times practically conctant) melts the electrode and adores an arc.



  In the order conditions by. impulse of the trans- t.rt, the initial fusion is often difficult since the
 EMI24.4
 oAverage available current is intentionally low and, in many cases, the increased levels are too infrequent to be
 EMI24.5
 efficient * In order to promote instantaneous start-up * the systems described have a power supply ea oo-o1r0l.L1t

 <Desc / Clms Page number 25>

 at low voltage, with the current in the same direction as that used in the arc and this current is supplied through an isolation rectifier, as shown in figure 11. This run current *:

   circuit intended to melt the tip of the electrode only circulates when initial contact / established between the electrode and the workpiece and it shuts off automatically when the arc is established, since the combustion voltage of the arc (13 volte and more)
 EMI25.1
 is greater than the open circuit voltage of the starting current supply and the rectifier potential is reversed.

   Voltages for suitable starting supplies range between 8 and 12 volts and, with a short circuit current of the order of 1000 amps, the first contact point melts almost instantaneously, usually in less than 1 hour. a
 EMI25.2
 However, not referring to the basic systems shown in Figures 1, 3o 7 and 9t the switching device can be assumed to be a simple normal rotary switch having metal carbon brushes.

   Bitin that this can be applied and that you choose any gold and any
 EMI25.3
 which pulse interval, it does produce some spark formation (arc initiation) at the start of the break, which for: r6su.ltnt wear c4lan sweeps and odeautatoure Cool can be reduced to a minimum for success griot to an * or more of the following provisions s use dta11..ntat1ok low taa- f
 EMI25.4
 810n (as in the case of self-tuned arc operation), in which the voltage difference between the power source and the welding arc is insufficient to allow arcing at the switch as well,

   minimizing the inductance of the circuit in the increased current flow, adding arc suppressing circuits in parallel with the break points, for example a capacitor in parallel, simultaneously establishing more a break in series, and so on. However, a variation is to use a slide '

 <Desc / Clms Page number 26>

 Switchable electronic device such as a silicon controlled rectifier.

   With an AC power supply, the silicon controlled rectifier can be brought to conduction at any suitable point on the alternating current waveform (positive anode) and it will automatically turn off on the next pass. by zero of the voltage, when the rectifier potential is inverted However, with a direct current supply an artificial inverse potential must be applied to cut the silicon controlled rectifier.

   Systems for this purpose are well known and an example is shown in Figure 12, in the-
1 which, with the main / already conducting silicon controlled rectifier to provide the increased current, the auxiliary silicon controlled rectifier 2 is tripped so as to discharge the precharged capacitor 15, in order to invert the silicon controlled rectifier 1 and cause his cut.



   Yet another system uses two silicon controlled rectifiers * which can usefully provide the background and boost currents, respectively, while switching each other for start and cut. A typical circuit for a DC power supply is shown in Fig. 13, in which the mutual coupling capacitor 15 is successively discharged by each silicon driven rectifier to cut off the other.

   This system is thus independent of the supply frequency (as opposed to the examples as shown in Figures 4, 5 and 8) and any useful nominal ratio between the dart and the level of the increased and background current can be chosen. This system is particularly advantageous in that the frequency of the current pulses can be related to the consumption rate or the electrode supply rate. Thus, with a given pulse amplitude intended to cause the transfer of a certain amount of metal from the electrode, if the feed rate is reduced,

   a corresponding reduction in consumption is obtained by

 <Desc / Clms Page number 27>

   reducing the frequency of the pulses and therefore also the average current (which must also correspond to the desired consumption speed).



   However, with a simple alternating current source and a controlled rectifier (or a rectifier with switch), a fixed frequency range can be achieved by using a three-phase power supply as shown in Figure 14. Thus,! with a three-phase half wave, the frequency of the pulses have 150 (for a power supply at 50 second cycles) and reducing to a single phase or eliminating some half cycles or both! various sub-frequencies of 100, 75, 50, 37.5, 30, eto. do prof.
 EMI27.1
 daites.

   The impedance of circuit Z2 can obviously be one, one: to the rectifiers or be actually specific to each of them * Again, the power source for the raw current supply can be regarded as distinct from the source of. background current or be combined with it,
Every hay that a DC power source is required, this may be in the form of a battery, a dynamo or a transformer-rectifier group, while when an AC source is required, it can use an alternator or a transformer.



   CLAIMS
 EMI27.2
 IIIIM'III TIC # (# IHM
1. An arc welding system or the like, comprising a first electrode, a part constituting a second electrode and a power source connected in series with the first electrode and the part to supply a current for maintaining an arc between the first electrode and the workpiece, characterized in that means are provided for cyclically increasing the arc current flowing between the first electrode and the workpiece to bring it to a level at which a property away from the arc, such as spray transfer occurs.


    

Claims (1)

2. System according to claim 1, characterized in that the first electrode is a consumable electrode and the <Desc / Clms Page number 28> RMS open-circuit voltage of the system is much greater than the arc voltage between the consumable electrode and the workpiece, and so means are provided which are sensitive. to the magnitude of the alternating current voltage to advance the consumable electrode will move the workpiece at a rate which is a function of said arc voltage. 3. System according to claim 2, characterized in the means for advancing the consumable electrode towards the part are provided small liter sensitive to the amplitude of the increased tension cyclically rider. 4. System according to claim 1, characterized in that the first electrode is consumable and the values of the elements of the circuit aent such that the rms voltage in open circuit of the power source corresponds, substantially to the voltage. of the arc between the consumable electrode and the workpiece, means being provided for advancing the consumable electrode towards the workpiece at a substantially constant speed which is independent of said arc voltage. 5. System according to any one of the preceding claims *, characterized in that the power source intended to maintain an arc between the first electrode and the part and the means increasing the current of the aro each comprise a source of. DC power, either as a common power source for both, or as separate power sources incorporated on either side. 6. System according to any one of claims 1 to 4. characterized in that the power source intended for hand. maintaining an arc between the first electrode and the workpiece is a source of direct current power and the means for increasing the arc current by clicking on it includes an alternating current source. 7. System according to any one of claims 1 to 4, characterized in that the power source intended for main- <Desc / Clms Page number 29> holding an arc between the first electrode and the workpiece and the means for increasing the arc current each comprise an alternating current power source, either under the torso of a power source common to both, or under the form of separate power sources incorporated on either side, respectively. 8. System according to any one of the preceding claims, characterized in that the power source intended to maintain an arc between the first electrode and the part is designed to work continuously. 9. System according to any one of claims 1 to 7, characterized in that it comprises means for preventing the operation of the power source intended to maintain an arc between the first electrode and the workpiece when the means intended to increase arc current operate. 10. System according to any one of the preceding claims, characterized in that the power source for supplying a current to maintain an arc between the preferred electrode and the workpiece is intended to supply a current which without the increase. ; is insufficient to cause the desired property of the arc to occur. 11. An arc welding system according to any one of the preceding claims, characterized in that means! are; provided to apply a starting current between the first electrode and the workpiece in order to supplement the power supply from the power source to initiate an arc between the first electrode and the workpiece and other means are provided to cut the starting current when the arc has been struck * 12. Arc welding system or the like, as described above or in accordance with the accompanying drawings. BRUSSELS, August 1, 1963