US2482892A

US2482892A - Electrical control system

Info

Publication number: US2482892A
Application number: US703982A
Authority: US
Inventors: Keith E Barwick
Original assignee: Weltronic Co
Current assignee: Weltronic Co
Priority date: 1946-10-18
Filing date: 1946-10-18
Publication date: 1949-09-27
Anticipated expiration: 1966-09-27

Description

Sept. 27, 1949,- K. E. BARWICK 2,432,892

ELECTRICAL CONTROL SYSTEM Filed oct'. 18, 1946 INVENTOR. //:z'2% Z7 3417412 Patented Sept. 27, 1949 H ELECTRICAL CONTROLWSXSTEML Keith E. Barwi'ck, Detroit, Michn'assignon: to

Weltronio' Company, Detroit Michi, a corpora? tiomoflMichigan Application October 18, 194'6,;SerialN'o. 703,982 7 12.ClaimS.. (Cl- 315-2168) This invention reiates to electr-ical oontrol systems and is particularly-"directed toward an. improved and' simplifiedmeans for controlling antomatic welding equipment of the-impulse type.

The p i l. objects-of this'inventionareto provide a simplereliable, and-efiicient control of the. aforesaid type; to provide Such a control which, when once energized; willmaintainitself energized until the completion of'-'a;i=ull welding cycle irrespective-of the condition of the inn ti'ating switchgto providein suoh control a trans- Former havinga plurality" of primary windings !arranged inloucking relation; and to generally simplify controls of thetypedescribed.

With the above; aswell-asctlher more detailed objects in' view which appear from the following description and the appended claims, therei s shown in the-drawings: preferred but illustrative embodiment of the invention;

In the drawing which is tone-taken as apart of this specification there-isillustrated diagram maticaliya controf system embodying the-inven tion. r

The control system comprises initiating'net n work 2, .a sequence network I a"- t-i-ming network 6', a firing network 83 and a power network l oso constructed andarranged that the initiatingnet'- work- 2" initiates operation *ofthe sequence network '6 which controls the timing network 5 which in. turn energizes thefiringnetwork 8 for rendering the'power network 0 conductivei The initiating network 2 comprises a pairof discontinuous type 'grid -controlledleading and trailing electronic valves V'tand V2 and a pair,

- valve SV, the other terminal of rthevalveSV being. connected to the iine' L2. The grid of the valve VI is connected through apa-rallell'y arranged resi-stancejand capacitor to the upperterminal' of" the secondary windingof the transformer T1 and the "intermediate terminal of this winding is connectedto" the cathode of the-valve 'V:l whereby the upper half ;l"1- of thiswinding is operable .to bias'the gridof: the vaiveViwith respect to its'icathode". "I heiower halfof t is same winding of the transformer .TI'' is :usedias-a primary winding and white hereinafter -ref erredfto ,asprimary winding l8.

A resistor Rlis connected across the terminals of the primary winding lit has an intermediate tap connection whichisconnected 'hy means of conductors 2| and 22'- to the line 132 A condenser "Cl is arranged in paraiiel withthelowerportion of the resistor'Rt, and a condenser G2 is connectedbetween the lower terminator the primary winding 1 8 and the npper' terminalof the secondary winding t1.

The primary .winding oith transformer T1 has a center tanconhection"dividingit into primarywinding and primarywindi'ng 26; A conductor '27- having inseries therewith a parallelly arranged resistor R3 and condenser 03- connects the centertan-or'common terminalof the winding-s 2E and '26 tic-the conductor 22'- connectedto IineLZ Theupner'terminal-of thewinding 26 is connected througlrthecontact a of a time-delay switcl-r TD and throughthe normally open contacts of a manually operated initiating switch SWI to the line Ll while-thedower terminal of thewinding fl 'i's-directly con-nected by means of conductor 28*to-the-l ine ht. The-transformer T2 is arranged to revide-a control'loiasrfor the valve V2 and has the upperterminal of its secondary winding connectedthrough a parallelly arranged resistor and capacitor tothe' grid thereof and its center tap connection directly connected to the cathode thereof; 7 A a'pac-itor C4 is connected between the terminals of lthe secondary winding of thetransformer TZfbr phasecontrol. The up- .per half of the -prirnary' Windingof the transformer T2 is in zlarailel circuit relation with the valve 'SV, itsnpper'terminalheihgdirectly connected to terminal i6 and-its certter tap being connected through a resistor R54 to theline L2. The lower half pfthis primary windingis connected between' theiines-Ei and L2- in series with the resist-MR4.

The sequencenetwork '4 comprises a plurality of discontinuous-type grid-controlled valves to one tcrm-i'na-lof separatesecondary windings of a transformer- T3, theprimary winding of wh-i'ch is connected hetween the-linesLl and L2.

The-terminals of" the secondary windings of the transformer T3 opposite-those connected to the anodesoff -the--va lves V3-'V8 are connected through impedance networks comprising para-llelly arranged capacitorsand resistors to a comcondenser C and variable resistor R5, while the impedance networks associated with the valves V4 and V6 each comprise a condenser C6 and a resistor R6 arranged in parallel circuit and having their values so related with respect to each other that each condenser C6 is operable to discharge through its resistor R6 in the time required for the lines LI and L2 to go through two or three complete voltage cycles.

The conductivity of each of the valves V4-V8 is controlled by the valves V3-V| respectively, since the grids of these valves V4 -V8 are each connected through resistors to the'terminal of the impedance network of the valves V3V'l respectively opposite to that which is connected to the common bus 32, so that, for example, if valve V3 is conducting, the grid of valve V4 will be negative with respect to the bus 32. The conductivity of the valve V3 is controlled by a transformer T4 having a secondary winding, one terminal of which is connected through a parallelly arranged resistor and capacitor to the grid of valve V3 and the other terminal of which is directly connected to the bus 32. The primary winding of the transformer T4 is divided into two parts by an intermediate connection providing primary windings 33 and 34. The winding 34 is connected in shunt with the solenoid valve SV by the conductors 35 and 36 connected respectively to the conductors I4 and 21. Conductor 35 is also connected to bus 32 whereby the potential thereof is held at the potential of the terminal l6 of the valve SV. The winding 33 is connected between the lines LI and L2 in series with the switches SW! and TD and a single operation-repeat operation switch SW2. As will be more fully described hereinafter, the valve V3 is normally maintained conductive due to the normally de-energized condition of the winding 34 and valve SV, but is rendered in a nonconducting or blocked condition when either or both of the windings 33 and 34 are energized.

The timing network 6 comprises a valve V9 controlled by the network 4 and a pair of back-toback arranged leading and trailing valves VH1 and VI I. The valve V9 has two controlling grids, either one of which, when biased negatively, will prevent the valve from becoming conductive. The cathode of the valve V9 is maintained at the same potential as the bus 32 by a conductor 31' which connects the bus 32 to the cathode of valve V9. One of the controlling grids is connected through a parallelly arranged resistor R1 and capacitor C! to the grid of the valve V4, while its other grid is connected through a resistance R8 to the grid of the valve V1 so that valve V9 is operable to conduct only during that time that both the valves V4 and V1 are conductive. The anode potential for the valve V9 is supplied by a transformer T5, the primary winding of which is connected in parallel with the solenoid valve SV by means of a conductor 38, having a manually operated weld-no weld switch SW3 and a pressure-actuated switch SW4, connected from one terminal of the primary winding to the line L2 and by a conductor 40 which connects the other terminal of the primary winding to the bus 32. It will be noted that the bus 32 is connected by conductor 35 to the conductor 14 which is in turn connected to the terminal I6 of the actuating coil of the solenoid valve SV. 4

One terminal of the secondary winding of the transformer T5 is directly connected to the anode of the valve V9, while the other terminal is connected by conductor 42 to the cathode of the valve VII). The grid of this valve is connected by a conductor 44, having in series therewith a parallelly connected resistor RH] and capacitor Clo, to the cathode of the valve V9. A capacitor CM is connected between the cathode of valve V3 and conductor 42. One terminal of the secondary winding of a transformer T6 is connected to conductor 42 and the other terminal of this secondary winding is connected through a parallelly arranged resistor R9 and capacitor C9 to the grid of the leading valve Vlll. A resistor Rl2 is connected between the grid and cathode of valve V15 to insure that the valve Vlfl conducts immediately after the valve V8 conducts and the anode of valve Vlil is positive. The primary winding of the transformer T6 is connected between the lines LI and L2 by conductors 45 and 48 so that it is continually energized as long as the line switches LS! and LS2 are closed and is polarized so that its output voltage will be effective to render the grid of the valve V10 negative whenever the potential of the anode of the valve VI 5 is positive with respect to its cathode. However, when the valve V9 is conducting, the potential of transformer T5 opposes that of the transformer T6 so that the grid of the valve Vil'l'will be properly biased to permit the valve Vlll to conduct.

The anode of the valve Vifi and the cathode of the valve Vll are connected together and to the line L3 by a conductor 58, while the cathode of the valve VH) and anode of the valve Vii are connected together and to line L4 by a conductor 52 having in series therewith the primary winding of a kick transformer Tl. The primary winding of a transformer T8 is continually connected between the lines L3 and L4, one terminal being connected to the conductor 55 by a conductor 54 and the other terminal being connected to the portion of the conductor 52 between the transformer T1 and line L4. One terminal of each of the secondary windings of the transformers T1 and T8 are connected together by a conductor 55. The other terminal of the secondary winding of transformer Tl is connected through a parallelly arranged resistor and capacitor to the grid of valve VI I, while the other terminal of the secondary winding of the transformer T8 is connected through the conductor 54 to the cathode of valve VI I. The voltage of the transformer T8 is such that it is efiective, when acting alone, to render the grid of the valve Vll negative with respect to its cathode whenever the anode of valve VH is positive with respect to its cathode. The kick transformer T7 is arranged so'that Whenever the valve Vlfl is conductive during a half cycle of current, the collapse of flux therein holds the grid of the valve VII in condition to permit the valve Vii to conduct during the subsequent half cycle. The valve VII therefore will not conduct unless the valve Vlll has conducted during the preceding half cycle and will always conduct during a subsequent half cycle to a half cycle that valve VII] conducts.

The firing network 8 comprises a transformer T9, a saturable reactor 56, and a current-limiting reactor 58. One terminal of the primary winding of the transformer T9 is connected by a conductor to the conductor 42, while the other terminal is connected through the saturable reactor 56 and current-limiting reactor 58 to one terminal 62 of a welding transformer WT having its other terminal directl connected to the line L4. A switch SW4 is arranged to shunt out the reactor 58 when lines L3; and L4 are supplied reassess with" 220=volt. power" and to opened" when 7 {Mill-volt" power is being supplied? When" the valves V I andLV'll are conducting current will flow between the lines"L3;"and?I-i4' through" the conductor 58, valvev'lflor"V1'l,i,conductors 52 and" 6t, reactors 56fand -58, and the Welding transformer WT"to' energize the transformer T9? Apair ofsecondary-'wirrdings'oftransformer T9 are-connected respectlvelrthrouglr rectifiti's Ell-"and 86470 the igniters and"cathodesofmer cury pool-type"-power=controlling *valves-v l'z and V'l3" respectively: It* wil l be" noted" that when the valves-V lli' and"Vl"l"cond1ict, the transformer T9 and reactors (hand 58 "are in" p'arallel circuit with thewalves V|2and'- V P3? and the" potential thereacross is the potential betweenthe-cathodes and anodes of the poweFcontrolli-ng' valves: Therefore;when thewalves Vl or Vl3 fire; the igniters are" practicallyde=energizedy and no deteriorating voltage i'smaintained onthe igniter of the valves 'Vl '2"an'd V t3? Reactor5'8 is adj ustable in its timerofsaturationt'oprovide forfir ing' the valves V I 2" and V Hi adjustable points alongthevoltage wave-between" the-lines I23" and L4--to-provide for controlling the welding heat as is more-fully--described=' and-claimed-in the co-= pending application-0P letus-=J i oilorn,-' Serial No. 681,758; filed='July- 65 19465 and assigned to the'same a'ssignee as i's-the-present invention;

' It is thoughtthatthe-remaining detailsyof'the system may best be understood with reference to a description of the operation thereof. Assuming; that it is "desiredto condition theisystem forrepeat-operati'on; the switch- SW2 is opencircuitedan'd- 'the usual -disconnect line switches LSP and-'LS2' are'-'closed-, therebyconnecting the lineconduct'orslll and L'Ftothesourceof supply which maybe a conventional GO cycle alternating current 1l0'-volt* system: The disconnect line. switches LS3 -and-"L'Sfl; which may bemechanically connected to the switches" LSI and LS2; are also closed; thereby connectingthe line conductors E3 and BF to-a suitable source of supply which ma be -a-- conventional (Sir-cycle alternating current 220 on 440=volt system,

switch SW i beingset accordingly-as hereinbefore described.- Erlergization 0f the lines Iil and L2 energizes primar winding- 24 of-the'transfonner T! I and the lower h-al-f=- of fthe primarywindin'g of thetransformer-{I 2 whereby-a--biasingvoltage is applied between' the grid andcathode' of the valves V1 and V2 respectively- 'to-maintain the valvesin a bloeked condltionr Closure of' the line switches-LS1 and--ESZ also energizes the transformer T3 having a secondary winding; the terminals of which; 'as--ii'1dicated Icy-the letters ma: appearing-"0n the-winding and on the cathode heaters, are connected to energize the cathode heaters' of the valves- -Vl vl l inclusive; The transformers Tfi and Tlhwere alsoenergized upon closure of the line:switchesBSI a-ndESE tQ pro vide respectively: a blockingbias voltage between the-grid and cathoderofifthe-valVes:-V le and V i 1i Glosure; of? the; line" switche'sazllsiit'. and: Lslltzpree pared the:- firingmetwork: & andsthe' power net.-' work: ilixfor: operations-by theenetwork; 4- Enemgization-of- -the-.-transformem'Il3-saiso energized the time-delay? means TD- whichsispoperable after a predetermined. timewdelay to closeits contacts 11, whereby -v theinitiating,i network limay be operated the. closure of'.the .switch' 'SWI. As soon as the valves V3- -V8 inclusiveare allfrendered in an operative condition due toheating "ofth'eir cathodes by their" respective cathode heaters," the valves V3, V5? andV'Fwi'll becomeconductive placed across the primary windings 33"'and' 34;

and therefore the grid of the valve" V3" will be at the same potential as the cathode thereof due to its-int'erconnectionthrough the secondary winding of thetransformer T4 which is connectedbetweemthe-grid and common" cathode bus 32}; Conduction" of the valve vscauses' a potentiatdrop to appear across the time-delay means T133whichma-intains th'egri'd of the valve V l negative with-"respect to the bus 3-2"a-nd the va1ve-V4 blockedr Since nocurrent is flowing in the anode' circuit ofthe valve V4; there will be no drop across the impedance network thereof comprising the" resistor R6 and capacitoncfi so that whe -grid of the -valve=V5=will-=beat the same potential as the cathode thereof" and this valve wil l-be= conductivea Conduction of the valve V5 causes a potentialdroptoappearacross the time del'ay network TD5 which -will maintain the grid of "the-valve V5 hegativewith respect to the cathodethereof, and-the--valv -V6 will therefore be in a blocked condition; Sinceno current is flowing through: the impedanc'e network of the valvevtg: the grid of thevalve V-F'Will be maintainedat the same potential as the cathode thereof," andthe valve VT will 'hein a conducting condition, causing current to flow through its time -delay"networ-k TDT, thereby maintaining the grid ofthe valve V8 negative'--with respect to the cathode thereof; and- 'th'e valve V8 will be heldiblocked; The" rig-ht-h-and grid of the valve V9. which. isconnected to-thegrid'--of thevalve Vk will beirnaintained at thesameipotential with respect; touits cathode as the grid of the valve V'lfwithz respect to its-cathode: I

Since the valve VE:.:is: not: conducting, V the conductor 96: which? is; electrica'll y'- connected to the terminal of the impedance-network: oh the valve VltoDDosite to' th'at connected to thebus -32:and' to the grid0f31 the valve VI: is conducting-current from: the upper terminal-Q of. the w-inding 17 through the impedance net-work TD8,- the common". busi32r: and conductor 35 backi to the lowerttermina'lxofCthe'winding Hi? This conduc tion: is without anyoperational effect uponthe system; since the: potential 'suppli'edbythe wind ing it? is quite sufiicient to maintain the grid in a condition to -block-the valve VI inspite of the added potential drop =through the resistor in the grid circuit ofithe valve VI:

Before a: stabilized condition of: the valves V-3-V8 isv reached; certain: of these valves may fire out oia' orders because- Ofithe fact that they have notas yet had the proper biases placed between their:grids andcathodesi Such operation is-withoutjeffect; however, due" to the; open condition: ot the: switch SW4- which is. controlled bythe outlet fluid pressure: of the solenoidrvalve SV; The: switch SW4 is closed. only when: the valve SV is inopen positi'on :and-i adpredetermined fliiid pressure is :being- =supplied 'to hold the: weld= ingelectrodes E against the work W: The solenoid valve SV has not: as yet been energizedcbecause. of the biasb'eing continually placed. between the gridand cathode 'of the valves V I and VZx-by the transformers-Tl and -TZJ The valvesmvlflif and V13-- can= onlyfire s-ub'sequent to :thefiringmf'zthe valves V10 and Vl l; and thesezvalves: areilikewis'e continually maintained in a blohedi condition After a predeterminedf ti-iner delay;- whiohui's sufiiciently ample to permit all of the valves V3-V8 to come to their stabilized condition, the networks 2, 4, 6, 8, and ID are ready for operation. Before a welding cycle can be initiated, the switch SW3 must first be closed. The switch SWI is then closed, energizing the primary winding 26 of the transformer TI, which energization acts to buck the flux in the core thereof due to the primary winding 24. This removes the blocking bias between the grid and cathode of the valve VI and the valve VI conducts. Conduction of the valve VI causes current to flow from the line LI through the conductor I2, the valve VI, conductor I4, and the energizing coil of the solenoid valve SV to the line L2. At the same time, current also flows from the line LI through the upper half of the primary winding of the transformer T2 and the resistor R4 to the line L2, through the winding I8 of transformer TI, the lower portion of the resistor RI and capacitor CI, and through the primary winding 34 of transformer T4, which circuits are in shunt relation to the valve SV.

Current through the winding I8 aids the current flow through the winding 26 in its bucking effect of the flux produced in the core of the transformer TI by the current flow through the winding 24. If the switch SWI at this time is still in closed position, this is without substantive effect on the operation of the network 2 other than to place on valve VI a bias somewhat more favorable to its already conductive condition. Current flow through the winding 34 of transformer T4 places a blocking potential between the grid and cathode of the valve V3 and renders the same nonconductive at the end of its conducting half cycle. Current flow through this upper half of the primary winding of transformer T2 tends to buck the fi-ux due to current flow through the lower half of this primary winding so that, at the next half cycle of the voltage wave between the lines LI and L2 when the anode of the valve V2 becomes positive with respect to the cathode thereof, the grid of the valve V2 will not be immediately rendered negative with respect to the cathode thereof due to the phasing effect of the capacitor C4 and the impedance of the primary winding of the transformer T2 so that the valve V2 will become conductive. Conduction of the valve V2 again establishes the circuit through the energizing winding of the solenoid valve SV and the windings I8 and 34 and upper half of the primary winding of transformer T2 as above identified, except that it flows in the opposite direction and through valve V2 instead of through valve VI. As the flux collapses in the core of the transformer TI at the end of the half cycle in which the line L2 is positive with respect to the line LI, the condenser C2, which was charged during this time, discharges through the windings I I and I8 arranged in series connection which opposes the build up in flux in the core of the transformer TI due to energization of the primary winding 24, so that the grid of the valve VI is not rendered negative with respect to the cathode thereof and the valve VI is rendered conductive. This subsequent conduction of the valve VI after initial conduction due to closure of the switch SW I will continue in the above-identified manner irrespective of the open or closed circuit condition of the switch SWI and will be terminated only upon completion of the full cycle of operation of the sequence network 4 in a manner to be hereinafter described.

After the circuit through the energizing coil of the solenoid valve sV was energized, the primary winding 34 of the transformer T4 was also energized as hereinbefore described. This caused a voltage to be induced in its secondary winding which biases the grid of the valve V3 negative with respect to its cathode to render the valve V3 nonconductive. This rendering of the valve V3 nonconductive is without immediate effect due to the potential maintaining feature of the time-delay means TD3. Subsequent to. a predetermined time interval after blocking of the valve V3, the capacitor C5 of the time-delay means TD3 will have discharged through its associated resistor R5 to render the grid of the valve V4 at the same potential as the bus 32. This time interval between the time that the solenoid valve SV was energized and the time that the time-delay means TD3 is timed out so that the grid of the valve V4 is rendered at the same potential as the bus 32 is the clamping or squeeze time of the welding apparatus-and represents the time interval between the time that the welding electrodes E1 were brought against the work W and the time that the valve V 9 is rendered conductive to initiate flow of welding through the welding transformer WT. As the time-delay means TD3 times out, the left-hand grid of the valve V9 will no longer be maintained negative with respect to the cathode thereof, and since the right-hand grid of the valve vs at this time is at cathode potential, the valve V9 will conduct and oppose the potential of the transformer T6 to render the valve Vi a conductive. As the valve VII) becomes conductive, current will flow from the line L3 through the conductor 50 through the valve VII) and conductors 32 and 6!! to the primary winding of the transformer T9. From the primary winding of the transformer T9, the current flows through the saturable reactor 56, the current limiting reactor '58, and the primary winding of the welding transformer to the line L4. At a predetermined time interv-al, which is always a fraction of a half cycle of the voltage wave between the lines L3 and L4, the saturable reactor 56 will saturate, permitting the critical voltage to be supplied by the left-hand secondary coil of the transformer T9 between the igniter and cathode of the valve VI2 to render the valve VI2 conductive. Conduction of the valve VI2 causes current to flow from the line L3 through the valve VI2 and the welding transformer WT to the line L4. Conduction of the valve VII'I also causes current to flow through the primary winding of the transformer T1 to the line L2, so that at the end of this half cycle during which the line Ll was positive with respect to the line L2, the collapse of flux in the kick transformer T! will induce a potential in the secondary winding thereof which overcomes the potential induced in the secondary winding of the transformer T8 so that the grid of the valve VII is not rendered negative with respect to its cathode before the valve VII conducts. Once conducting, the valve VII will permit current to flow from the line L4 through the primary winding of the welding transformer WT, the reactors 56 and 58, the transformer T9, the conductor 60, the valve VII and conductor 50 to the line L3. The flow of current through this just-mentioned circuit, depending upon the time taken to saturate the saturable reactor 56, will cause the critical potential to be applied between the igniter and cathode of the valve VI3 for rendering it conductive to permit current flow from the line L4 through the welding transformer WT, the valve VI3 back to the line L3.

ewa e .At the time the time-delay means 'ID3 timed out the valve V4 was also renderedoonductive, causing a potential 'tob'e established across its anode impedance .eircu'it, "thereby reifdering'the grid of the valve V negative with res ectto its cathode to block the v'alveV5. "Therender ing of valve V55 nonconductive is 'w'ithout immediate effect due .tothe "time-delay network -TD5 which maintains "the grid of the valve VB negativeand consequently the valve voblocked 'for..a .prede termined time intervalsubsequent to blockingof the valve V5. This time intervalis thewelding time, since at the expiration of this time interval the :grid of the valve V 6 "w'illbe rendered at cathode potential and valve V6 will become conductive. Upon conduction of valve V6 a .potential will be established across v-the impedance .network of its anode. circuit, rendering the grids" of the valves V and V9 negative with-respect to their cathodes andconseguently the valves nonconductive. The means TD5-therefore controls the welding time or vinterval whenvalve V9 is conductive.

Rendering of-the valve Vl' blocked without immediate -efi'ect,'=but--as soon as the-' time-delay means TD! times -out,'-thevalve V8 will be rendered 'conductivewbec'ause' its grid will then be' at cathode potential. The time interval represented by the time of themeans TDl is the hold'time or time that thecelectro'des Ear e held against the work -W during cooling'of the weld. i Conduction of the valveVB establishesap'otential 'acrossits time-delay means 'TDfi whic'h renders the potential of the conductor" 66: negative with respect to the bus 32 and 'withre'sp'ect to' the cathode of valve Vi Whichis connected thereto bythe conductors ill and ..:35."'The negative potential of the conductor 66 is ofsuilicient magnitude to hold the grid of 'thevalve VI negative with respect to its associatedcathode andfhold the valve Vl against subsequent fir ing, thereby de-energizing the solenoid valve ='SV-and pernii-ttingthveleotrodes E to'be released from the work W. The valve'VZ will not aga'in berendered conductive, since theupper half'ofthe-primary winding'o'f transformer T2 was 5 likewise "de-energized, permitting the lower half-ofthis winding to bias the valve V2 nonconductive. I

Winding "34 which is also in parallel circuit with the valve 'SV is also d'eeenergizedi to initiate the resetting cycle of operation "of the sequence networkd by removing theblocking'b'ias onvalve' V3 so that it is rendered conductive. Conductionof valve V3 ire-establishes the potential drop across its anode impedance network rendering the-valve Vii blocked which rem o'ves the bloekin'g biason the grid of valve V5. Valve V5 then becomes conductive, 'establishing,'du'e to "the potentialdrop across itstime-delay means T135, ablocking bias on the grid of valve'Vt, rendering this valve nonconductive. With valve V6 n'onconductive, the grid of valve Vl goes-'to oathodepotential, and valve 'V'l becomes conductive, ire-establishing a potential drop across its "time-delay means'T-Dl, rendering the grid of valve V8 negative with respect to its cathoda and valve V8no'nconductive. Rendering of valve V'8 blocked iswithout immediate e'fiect, duetogthe action -01: 'the'ti'm'e-delay means TDB which will maintain a potential thereacross for a predetermined timeinterval subsequent to the blocking iofthevalve This'interval is the ofinme peneaof'the welding-machine or time when i the electrodes E are maintained parted.

As the time-delay times out, the

iv dfsaid first controlling "iiieans "ior 'rendering negativewpotential. impressed thereby. on the grid of'the valve 'vl disappears, and, assuming the switch SWI to.be closed indicating-that'the'desired. welding has 'nb'tlbeen cemented, the valve Vi williagain 'be rendered conductivein the same mariner .as is described herei'nb'fore, and the weldingicycle will "be repeated. If, however, the sw-itc'h SW1 has been. opened, the networks will remain in'this stable. condition until "the switch SW1 is again closed, because theonlylprimary or input winding of "the transformer'T'l which is energized is windingid, .and the eifect of this winding is I to maintain v'a'lve 1V1 iblocked.

-Ii now the sw'itchS'Wlhad been in closed -circuitor single-weldposition-the cycle ofoperation just {described in ..connection with the repeat w'eld or open-circuit condition of switch SW2 would'bel'iriterrupted'at thel time valve V8 was rendered conductive and betore theresetting-cycle of network 4-was initiated. interruption is due toftheenergization ofthe windingteof transforme'r'T4, whichis .p'oflarfizedso that curreritflow therethrough .aids the'current flow through the winding 34 in p'laei'nga blockinglbiaspotential on the grido'fthe valve' V3. 'The vallvelfi, therefore, will remain in a blocked orlnonconductive condition, even thoughlthe w1n&in 4: d-e-energ'ized dueto the nonconductive conditionof the valves V l. and "V2. 'Sincethe valve Vl'iis maintained blocked, the ntworlail can-notgo through its resetting cycle of operation andwill-remain in that condition "as longas thesw itch swl remains closed. Opening OfthQ-SVitChjS'Wl de-energizes thew'in'ding 33, permitting valve V3:to become conductive and the resetting cycle of network l tooccur: in themanner h described in connection with the repeat operation. 115, however, the switch SWI is openedprior-tothecompletion of the initiaLportionof the"operation of "the sequence networ kd the-weldingcycle will continue through. its. resetting cycle .-just-as the switch SW; rwerein repeat or open-zpos-ition, but, as set forth with respect to the repeat operation, another welding cycle-will not :beinitiated, because atthis time only thew-hiding?! o'fltransformer T l. is?energized,'fland"this winding acts to hold the valveiv'l blocked.

Ihe 's'witch SW3 is normally maintained in closed circuit position butmay be'opened 'in the 4 event it is 'desiredto "go throughall ofzthe welding steps without-welding current -actually flowing. Switch SW4 prevents welding cur-rent from flowin'g'in'the event the'iiuidpressure to the electrodes failsffor any reason.

.Althoughonly ae-sing-le specific embodiment of the invention has-been: disclosedtin-detail, itw-ill be -appreciated -that various modifications in the form,- number, and: arrangementt'ofqaarts may be made without departing from the spirit and scope 0f the invention.

What is claimedandis'desired to 'be'secured by Tinited States'LettersTatent is as'fo'llows:

1. in an electrical controlling network, electronic valvemeans having a cathode and a controlling gridypotentialsupplying means electric'a'lly 'connectedbetwe'en';said"cathode and said grid 'for applyingabi'as potential to eontro1 the conduction of saidvalve means, means for controlling the magnitude fol? said, potential applied hetwe'en' said -cathode and'said grid and operable uponenerg'ization' to'rendersald supplying means ineffective to 'supplys'a'i'd bias'potential, and a second controlling means"energizediindependent- 11 said supplying means inefiective to supply said potential.

2. In an electrical controlling network, a pair of electronic valves connected back to back, one ofsaid valves having a cathode and a controlling grid, potential supplying means electrically connected between said grid and said cathode for biasing said grid with respect to said cathode for maintaining said one valve nonconductive, means rendering said biasing means ineffective to supply said potential, and means energizable as a consequence of an operating condition of the other of said valves for rendering said biasing means ineffective to supply said potential.

3. In an electrical controlling network, a transformer having a single core and a plurality of windings, each said winding having a pair of terminals, an electronic valve having a cathode and, a controlling grid, circuit means connecting the terminals of one of said windings between said grid and said cathode, circuit means connecting the terminals of another of said windings across a source of electrical supply potential, and means electrically connecting the terminals of a third of said windings to said supply potential in opposite polarity relative to the connection of said other winding whereby current flow through said third winding opposes the build up of flux in said core due to flow of current through said second winding thereby to vary the voltage output of said first winding.

4. In an electrical controlling network, a pair of terminals adapted to be connected to a source of alternating current supply, a pair of electronic valves, each of said valves having a cathode and an anode and a controlling grid, circuit means connecting one of said terminals to the anode of one of said valves and to the cathode of the other of said valves, circuit means connecting the other of said terminals to the cathode of said one valve and to the anode or said other valve, translating means in series circuit with one of said circuit means, transformer means having a first winding connected between said terminals and a second winding connected between the cathode and grid of said one valve, a third and a fourth winding for said transformer means, a controlling switch, a circuit connecting said third winding to said terminals through said switch, and a circuit connecting said other terminal through said fourth winding and one of said valves to said one terminal.

5. In an electrical controllingnetwork, a pair of terminals adapted to be connected to a source of alternating current supply, a pair of electronic valves, each of said valves having a cathode and an anode and a controlling grid, circuit means connecting one of said terminals to the anode of one of the valves and to the cathode of the other of said valves, circuit means connecting the other of said terminals to the cathode of said one valve and to the anode of said other valve, translating means in series circuit with one of said circuit means, transformer means having a single core, a first transformer winding connected between said terminals and a second transformer winding connected between the cathode and grid of said one valve, a third and a fourth transformer winding for said transformer means, a controlling switch, a circuit connecting said third winding to said terminals through said switch, and a circuit connectingsaid other terminal through said fourth winding and one of said valves to said one terminal, said first winding being operable to induce a flux in said core in one direction whereby a bias voltage of one por 12 larity is applied by said second winding to said one valve, said third and fourth windings being so polarized relative to said first winding that current flow through either thereof will oppose the flux in said core due to current flow through said first winding.

6. In an electrical controlling network, a pair of terminals adapted to be supplied with alternating current energy, a working circuit between said terminals including a pair of back-to-back arranged Valve means, whereby alternating current fiow therethrough may be controlled, each of said valve means having an anode, and a controlling grid and a cathode, a transformer having a single core and a plurality of windings about said core, one of said windings being connected between the grid and cathode of one of said valves, a second of said windings being connected between said terminals and arranged'to render the potential of the grid of said one valve negative when the potential of its respective cathode is negative with respect to its anode, a switch, a third of said windings being connected through said switch to said terminals and arranged to buck the flux in said core due to said second winding, and a fourth of said windings connected to said terminals through the other of said valves.

7. In an electrical controlling network, a pair of terminals adapted to be supplied with alternating current energy, a working circuit between said terminals including a pair of back-to-back arranged valve means whereby alternating current flow therethrough may be controlled, each of said valve means having an anode and a controlling grid and a cathode, a transformer having a single core and a plurality of windings about said core, one of said windings being connected between the grid and cathode of one of said valves, a second of said windings being connected between said terminals and arranged to render the potential of the grid of said one valve negative when the potential of its respective cathode is negative with respect to its anode, a switch, a third of said windings being connected through said switch to said terminals and arranged to buck the flux in said core due to said second winding, a fourth of said windings connected to said terminals through the other of said valves, and capacitor means connected to said first winding whereby it is operable to discharge therethrough to provide a lagging output Voltage for said second winding relative to that between the anode and cathode of said first valve means.

8. In an electrical controlling network, a pair of terminals adapted to be supplied with alternating current energy, a Working circuit between said terminals including a pair of back-to-back arranged valve means whereby alternating current flow therethrough may be controlled, each of said valve means having an anode and a controlling grid and a cathode, a transformer having a single core and a plurality of windings about said core, one of said windings being connected between the grid and cathode of one of said valves, a second ofsaid windings being connected between said terminals and arranged to render the potential of the grid of said one valve negative when the potential of its respective cathode is negative with respect to its anode, a switch, a third of said windings being connected through said switch to said terminals and arranged to buck the flux in said core due to said second winding, a fourth of said windings connected to said terminals through the other of said valves, ca-

pacitor means connected to said first windin whereby it is operable to discharge therethrough to provide a lagging output voltage for said second winding relative to that between the anode and cathode of said first valve means, and means for limiting the magnitude of current flow through said second and third windings.

9. In an electrical controlling network, a pair of terminals adapted to be supplied with alternating current energy, an inductive working circuit between said terminals including a pair of backto-back arranged valve means whereby alternating current flow therethrough may be controlled, each of said valve means having an anode and a controlling grid and a cathode, a transformer having a single core and a plurality of windings about said core, one of said windings being connected between the grid and cathode of one of said valves, a second of said windings being connected between said terminals and arranged to render the potential of the grid of said one valve negative when the potential of its respective cathode is negative with respect to its anode, a switch, a third of said windings being connected through said switch to said terminals and arranged to buck the flux in said core due to said second winding, a fourth of said windings, capacitor means connected to said first winding whereby it is operable to discharge therethrough to provide a lagging output voltage for said second winding relative to that between the anode and cathode of said first valve means, resistance means connected across the ends of said fourth winding and having a tap intermediate its ends, circuit means connecting said tap to one of said terminals and one of said fourth winding to the other of said terminals, and capacitor means connected between said tap and the other end of said fourth winding.

10. In an electrical controlling network, a pair of terminals adapted to be supplied with alternating current ener y, a working circuit between said terminals including a pair of back-to-back arranged valve means whereby alternating current flow therethrough may be controlled, each of said valve means having an anode and a controlling grid and a cathode, a transformer having a single core and a plurality of windings about said core, one of said windings being connected between the grid and cathode of one of said valves, a second of said windings being connected between said terminals and arranged to render the potential of the grid of said one valve negative when the potential of its respective cathode is negative with respect to its anode, a switch, a third of said windings being connected through said switch to said terminals and arranged to buck the flux in said core due to said second winding, a fourth of said windings connected to said terminals through the other of said valves, capacitor means connected to said first winding whereby it is operable to discharge therethrough to provide a lagging output voltage for said second winding relative to that between the anode and cathode of said first valve means, and capacitor means in series circuit with said second and third windings.

between the grid and cathode of One of said valves, a second of said windings being connected between said terminals and arranged to render the potential of the grid of said one valve negative when the potential of its respective cathode is negative with respect to its anode, a switch, a third of said windings being connected through said switch to said terminals and arranged to buck the flux in said core due to said second winding, a fourth of said windings connected to said terminals through the other of said valves, capacitor means connected to said first windin whereby it is operable to discharge therethrough to provide a lagging output voltage for said second winding relative to that between the anode and cathode of said first Valve means, and a second means for biasing the grid of said one valve independently of said first Winding.

12. In an electrical controlling system, a sequence controlling network, an initiating network for initiating the operation of said sequence network including a pair of back-to-back arranged electronic valves each having a controlling grid and a main electrode, transformer means having a secondary winding and a plurality of primary windings, each said winding having a pair of terminals, means connecting said terminals of said secondary winding between said grid and main electrode of one of said valves, to control the conduction of said one valve, means adapted to connect a source of potential to said terminals of one of said primary windings operable to normally maintain said. one primary winding energized whereby said secondary winding is operable to supply a potential to bias the grid of said one valve into a blocked condition, means for selectively connecting the terminals of a second of said primary windings to a source of potential in a direction to oppose the energization of said transformer means by said first primary winding, potential supplying means including the other of said valves connected to the terminals of a third of said primary windings for energizing said third primary winding, in a direction to oppose the energization of said transformer means by said first primary winding, and potential supplying means connected between said grid and said main electrode of said one valve and controlled by said sequence network for biasing said grid and said cathode of said one valve with respect to each other.

KEITH E. BARWICK.

No references cited.