Патент USA US2404971код для вставки
Jüäy 3g’ 1945’ J. R.,CONTROL MAHGNEY CIRCUIT 5T AL Filed Aug. 19, l1944 W‘TNESSES: '2' 2 Sheei‘S-«Sheâ‘î- 2 ì HNVENTQRS Patented July 30, _1946 ‘ UNITED 2,404,971 STATES PATENT OFFICE 2,404,971 CONTROL CIRCUIT John R. Mahoney, Pittsburgh, and Harry J. Bich sel, Forest Hills, Pa., assîgnors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 19, 1944, Serial No. 550,231 7 claims. (Cl. 32o-1) l 2 tifìer for charging the capacitor, would instead be passed through the series connected valve pre venting the latter from becoming non-conductive This invention relates to an electronic control circuit and has particular relation to a control circuit for use with a capacitor discharge Welder. In an energy storage Welder of the capacitor discharge type, a bank of capacitors is charged from an alternating current supply source through a rectifier and is thereafter discharged to enable a new weld to be made. It is therefore necessary to block the operation of the rectiñer during the time that the series connected valve is conductive. In the past, operation of the rectiñer during discharge of the capacitor bank has been pre through the primary winding of a welding trans former, the secondary Winding of which is con vented by means of an auxiliary timing circuit which was connected to the rectifier circuit and became effective at the time the series connected valve wasI rendered conductive.l The blocking nected across a pair of Welding electrodes in en gagement with the material to be welded. It has been common practice to control the discharge of the capacitor bank by means of an electric dis charge valve of the arc-like type, such as an ig time provided depended upon the voltage to which the capacitor bank had been charged. This ar rangement is also shown in the aforementioned copending application of Smith and Stadum. of capacitors. The series connected valve is ren An auxiliary timing circuit as described to block dered conductive by a timing circuit after the capacitor bank is charged to the desired voltage. the operation of the rectifier during the capaci >When the series connected valve becomes _con 20 tor discharge operation is effective for that pur ductive, the capacitor bank is discharged through pose. However, the actual length of the dis the primary winding of the welding transformer charge time varies considerably for different transformers and different numbers and sizes of to effect a Weld. capacitors employed. In actual practice, the As the discharge of the capacitor bank is com pleted, the energy stored in the magnetic core 25 number of capacitors employed in the capacitor bank may be changed at will for different jobs. of the transformer and the secondary circuit dur ing the discharge is released and tends to charge In addition, the control circuits may be applied the capacitol` bank inversely. To prevent such to different welding transformers. Since the inverse charging of the capacitor bank, a second overall blocking time is substantially constant in electric discharge valve of the arc-like type, pref 30 the prior circuits for any capacitor voltage em erably an ignitron, is connected in shunt across ployed, the timing circuit must be arranged to the primary Winding of the Welding transformer. give a blocking time of sufficient duration to take care of the longest discharge time. Such an ar The shunt connected valve is non-'conductive during the original discharge of the capacitor rangement obviously increases the overall time required for a welding operation in most cases bank but is rendered conductive when the energy stored in the transformer core and secondary and prevents the high speed successive Welding nitron, connected in series With the primary Winding of the welding transformer and the bank circuit is released. The current resulting from operations desired. ` the release of energy is shunted through the shunt connected valve and does not charge the ycapacitor bankinversely. Such an arrangement is shown, for example, in the copending applica tion of Clyde E. Smith and Clarence B. Stadum, Serial No. 475,662, filed February 12, 1943. It is accordingly an object of our invention to provide a new and improved control circuit for a capacitor discharge Welder. Another object of our invention is to provide a new and improved circuit for preventing charg ing of the capacitor bank during the normal dis . In many applications of capacitor discharge charge thereof in a capacitor discharge Welder. Welders, high speed operation is extremely de 45 A further object of our invention is to provide a novel control circuit for a capacitor discharge sirable. For example, when a series of welds are Welder in which' the speed of operation is con to be made in rapid succession, correspondingly rapid charging and discharging of the capacitor siderably increased. bank is required. The rectifier employed to In accordance with our invention the operation charge the capacitors in the bank is ordinarily 50 of the charging rectifier is prevented only in re arranged to supply charging current whenever sponse to actual current flow through the vvalve vthe capacitor voltage is below a predetermined means controlling the fiow of current between the `primary Winding of the welding transformer and 'desired value. If the rectifier is in operation at the capacitor bank. Thus, in a, Welder in which _L_thesame time that the series connectedvalve is l‘conductive, the current supplied through the _rec 55 a series connected and a shunt connected valve 2,404,971 Zi» are used as described, the rectifier is blocked only as long as the series connected valve is conduc tive. As soon as the series connected valve be comes nonconductive, recharging of the capac itor is initiated although current may still be flowing in the circuit through the primary wind ing of the welding transformer and the shunt connected valve. As a result the speed of opera tion of the welder may be greatly increased. the firing valve 69 and the ignition electrode ‘I5 . and cathode 65 of the valve 61 to the capacitor 3. larity in the appended claims. The invention it self, however, both as to the organization and method of operation, together with additional objects and advantages thereof, will best be un derstood from the following description of specific embodiments when read in connection with the - » type such as a thyratron has its anode -Il con nected to the anode 53 of the valve 6l. and its cathode 'I3 connected to the ignition electrode 'I5 of the valve 5l. Valve 69 is hereinafter desig nated as a firing valve. When the firing valve 59 is rendered conductive, current starts to flow in the circuit extending from the capacitor 3 through the primary winding 9, the resistor 6|, The novel features that we consider character istic of our invention are set forth with particu accompanying drawings, in which: 4 An electric discharge valve 69 of the arc-like Y Figure 1 is a schematic diagram illustrating our invention as embodied in a capacitor discharge Welder; and Fig. 2 is a schematic diagram illustrating our invention as embodied in a capacitor discharge Welder of a different type. As shown in Fig. 1 a variable capacitor 3 is connected to be charged from a source of alter This current renders the valve 61 conductive and the main discharge of the capacitor 3 is effected. The control circuit of the firing valve 69 may be traced from the cathode 'I3 through a source of biasing potential such as a battery ‘|`|, the secondary winding ‘I9 of a peaking transformer ‘6I and a grid resistor 83 to the grid 85 of the fir ing valve 69. The biasing potential supplied from the battery 'Il normally maintains the firing valve 69 non-conductive to prevent discharge of -the capacitor 3. However, a potential may be ap plied in the control circuit of the firing valve 69 through the peaking transformer 8| in a manner described hereinafter to render the firing valve 69 conductive. When the capacitor 3 is discharged, the cur nating current 5 through a rectifier charging cir rent flowing through the inductive primary wind cuit 'l and to be discharged through the primary ing 9 stores energy in the core of the welding winding 9 of a welding transformer i i. The sec transformer li as well as in the secondary wind ondary winding i3 of the transformer il is con ing circuit. As the discharge of the capacitor nected across a pair of welding electrodes i5 and 3 is completed, the energy so stored is released l'l’ which are adapted to be moved relative'to tending to maintain the flow of current through each other to clamp the material i9 to be welded the valve 51 to charge the capacitor 3 inversely therebetween. The charging circuit 'l receives its energy from 35 with the plate 4| negative and the other plate t3 positive. To prevent this inverse charging, a the source 5 through a circuit breaker 2| and second electric discharge valve 87 cf the arc-like an auxiliary transformer 23. The charging cir type, preferably an ignitron, is connected in shunt cuit includes a pair of rectifier valves 25 and 2l across the primary winding 9 and in parallel’with of the arc-like type, preferably thyratrons, hav ing their anodes 29 and 3|, respectively connected 40 the resistor SI, series connected valve 6'! and ca pacitor 3. The anode 89 of the shunt connected to opposite end terminals 33 and 35 of the sec valve 8l is, of course, connected to the same ter. ondary winding 3l of the auxiliary transformer minal 59 of the primary winding 9 as is the 23. The cathodes 38 and 39 of the valves 25 and anode 63 of the series connected valve 61.. 2l, respectively, are connected to each other and The firing circuit of the shunt connected valve to one plate ¿il of the capacitor 5. The other l @l may be traced from the cathode 9| through plate |33 of the capacitor 3 is connected to a cen a second capacitor S3, the anode 95 and cathode ter tap 45 of the secondary winding 3l. The grids 9i' of anotherelectric discharge valve 99 (desig 41 and t5, respectively, of the valves 25 and 2i nated as a firing valve and preferably a thyra are connected together through their respective The junction point be- , tron) and a resistor IUI to the ignition electrode grid tweenresistors the grid5I resistors and 5i and 53 is connected V23 of the shunt connected valve 8l. The'capaci tor 9S is charged from the alternating current through another resistor 55 to the cathodes 3l source through another auxiliary transformer and 39 of the valves 25 and 2l. Consequently, the |55, a rectiñer |01 and a resistor |09. Conse grids bil' and "i9 are normally at the same poten tial as the corresponding cathodes 38 and 3a. ,. quently, when the second firing valve 99 is ren dered conductive, the capacitor 93 is discharged As a result, the charging circuit 7| constantly through the ignition electrode |93 of the shunt tends to supply direct current through the capac itor 3 to charge it to a predetermined value of ìconnected valve 81 to render the latter conduc ive. voltage with the one plate ¿il positive whenever The control circuit of the second firing valve the capacitor voltage is below the predetermined . 99 may be traced from the cathode 91 through value. The value of the voltage is predetermined the resistor lill, the ignition electrode |03 and by the magnitude of the source voltage, the ad cathode 9| of the shunt connected valve 87, an justment of the capacitor and the other circuit other resistor III, a source of biasing potential constants. ` The positive plate ¿il of the capacitor 3 is ,. such as a battery H3 and a grid resistor I I5 to connected to one terminal 5l of the primary ' the grid I I'I of the valve 99. The biasing poten tial normally maintains íiring valve 99 non-con winding 9 of the welding transformer il with ductive. Another rectiner valve I I9 has its anode the other terminal 53 being connected to the other l2! connected to the anode 89 of the shunt 'valve plate ¿i3 of the capacitor tl through a small re sistor Si and the anode 63 and cathode 55 of 70 8| and its cathode |23 connected to the junction point between resisto-r III and battery II3,` When an electric discharge valve 6l of the arc-like type, the energy stored in the Welding transformer and such as an ignitron. Consequently, when the the secondary winding circuit is released, the valve B'I becomes conductive, the capacitor 3 is discharged through the circuit including the pri polarity across the primary winding> 9l changes mary winding 9, the resistor 5l and the Valve 5l. and rectifier valve H9 becomes conductive. The 2,404,971y current‘then flowing through rectifier valve ||9 25 and 21 until it. reaches a predetermined maxi-ä and resistor -| || develops a potential across re mum voltage. A hand switch |6| may then be closed completing a circuit from one terminal of the source through the coil |63 of a solenoid valve |55, the hand switch |6| and a commutator |61 to the other terminal of the source. The sistor ||| to render firing valve 99 conductive to elîect ñring of the shunt connected valve 81. When the shunt connected valve 81 becomes con ductive, the current flowing as a result of the commutator |61 is provided with conductive and release of energy at the primary winding 9 is non-conductive sections arranged to effect an conducted through the shunt valve. The series opening and a closing of the circuit at timed in connected valve 61 becomes non-conductive at this time as the anode-cathode voltage thereof 10 tervals for a predetermined period of time. The commutator may be driven by `a synchronous drops below the value necessary to maintain the arc therein. Another auxiliary transformer |25 has its pri mary Winding |21 connected across the small resistor 6| which is in circuit between the pri mary wlnding 9 and the series connected valve 61.' The secondary winding |29 of the trans motor |69 which is energized from the source. It is to be noted that the commutator |61 is merely illustrative of a repetitive timer and other timing means may be employed in place of the com mutator. In actual practice electronic circuits such as is disclosed in the copending application of Pearson and Faulk, Serial No. 442,939, liled former |25 is connected across a resistor |3| May 14, 1942, now Patent No. 2,354,140 dated July which in turn is connected across another resistor |33 and a gas discharge tube such as a neon lamp 20 18, 1944, are often» used for this purpose. When the commutator |61 completes the cir |35.- For reasons which will be set forth here cuit through the coil |63 of the solenoid valve inafter, the transformer |25 is one having sui'li |65, the lower valve member |68 is closed and the cient iron in its core and a sunicient number of upper valve member |1| is opened, completing a turns so that it will not become substantially saturated under the conditions in which it is to 25 hydraulic circuit from an inlet pipe |13 to an outlet pipe |15. The outlet pipe |15 leads to a be used, and will have a secondary winding out cylinder |11 containing a spring biased piston put voltage of substantially the same Wave form |19 to which one 0f the electrodes |5 is secured. as the voltage impressed across its primary wind ing. Hydraulic pressure forces thispiston |19 down Direct current voltage is supplied across a volt 30 ward until the electrodes |5 and |1 engage the material I9 to be welded, Thereafter, the back age divider |31 from the alternating current pressure in the hydraulic system operates through source through a transformer |39, a full Wave another pipe |8| to move another spring biased piston |83 to the left as illustrated in the draw ings. Movement of the second piston |83 to the left closes a contactor |85 to complete a circuitl from> a capacitor |81 through the contactor |85 and the primary winding |89 of the peaking trans iier tube such as a pentode |49, an RCA 6-C-6 former 8l, the secondary winding 19 of which is tube being satisfactory. The cathode |5| of th pentode |49 is connected to an intermediate point 40 in the control circuit of the iirst firing valve 69. The capacitor |81 has been previously charged |53 of the divider |31, the negative terminal |55 rectifier |4| and iiltering capacitors |43. The positive terminal |45 of the divider |31 is con nected through the resistor 55 in the grid to cathode circuit of the valves 25 and 21 in the charging circuit 1, to the anode v|41 of an ampli of which is connected through the neon lamp |35 and a grid resistor |51 to the control grid |59 of the Apentodel Thus, the magnitude of the cur rent flowing through the pentode |49, and con sequently through the resistor 55 in series there With, depends upon the voltage across the neon lamp |35. When the voltage supplied from the auxiliary transformer |25 is low, the pentode |49 from a source of direct current potential such as a battery |9I, connected thereacross. Thus, when the contactor |85 completes the circuit, the capac " itor |81 discharges through the peaking trans former 8| which impresses a potential in the first firing valve control circuit sufficient to render that valve conductive and fire the series con nected Valve 61. - is substantially non-conductive and no voltage is developed across the resistor 55 by current flowing When the series connected valve 61 becomes conductive, the main capacitor 3 is discharged through the pentode circuit. When the voltage through the primary winding 9, the small resistorl supplied from the transformer |25 is high, the pentode |49 is conductive and the current flowing therethrough develops a potential across the re sistor 55 of such magnitude and polarity as to prevent the valves 25 and 21 in the charging cir cuit 1 from becoming conductive. In other words, when the pentode |49 is conductive, the charging circuit 1 is prevented from operating. The neonv lamp |35 serves to limit the maxi mum positive voltage on the grid l|59 of the pentode |49 without disturbing the wave form of 6| and the series connected valve 61 to effect a weld. Current iiowing through the resistor 6| acts through the auxiliary transformer |25 to lm press a potential in the control circuit of the. pentode |49 causing the latter to become conduc tive. So long as the pentode |49`remains con ductive, current flowing through the resistor 55 the voltage supplied from the secondary winding circuit therewith develops a potential across co" in the resistor 55 which prevents the valves 25 and 21 in- the charging circuit of the capacitor 3 from conducting any current to the capacitor 3 or to the discharge circuit therefor.> , ' |29 of the transformer |25 during the very iirst 65 " It-is to be noted -that the only current through and very last parts of the discharge of capacitor the resistor 6| isthatïwhich 'passes through the" 3. It is only by having the Wave form of the volt seriesA connected valve‘61. This current is but a age developed across the secondary winding sub single unidirectional impulse. In addition, the voltage developed across the resistor 6| is often across the primary winding that it is possible 70 too low to be used directly in an electronic con trol since, in most cases, the resistor 6| must be to eiïect removal of the blocking potential from quite small to avoid appreciableeffec't in the dis the charging circuit at the proper time. I charge circuit. For these reasons an auxiliary yIn operating the Welder illustrated in Fig.` 1, stantially the same as the wave form impressed transformer _ |25 is used in _which the lvoltage the circuit breaker 2| is iirst closed. The capac-4 itor 3 is then charged through the rectifier valves 76 across the secondary winding has `the same `wave 2,404,971 Tí 8 form as the voltage across the primary winding. be traced from its cathode 215 through a source of biasing potential such as a battery 2 |1, the sec Such a transformer insures the impressing in the input circuit of the pentode |419 of a potential to maintain the pentode conductive substantially until the series connected valve 61 becomes non conductive. As the initial discharge of the capacitor 3 through the primary winding 9 of the Welding ondary winding 2|9 of a peaking transformer 22| and a grid resistor 223 to the grid 225 of the firing valve. The b-iasing potential supplied from the battery 211 normally maintains the firing valve 299 non-conductive to prevent discharge of the capacitor 3, However, a potential may be im transformer || is completed, the stored energy pressed in the control circuitI of the firing valve is released tending to maintain the flow of cur 10 through the peaking transformer 22| in a manner rent-through the series connected valve 61 to described hereinafter to render the firing valve conductive, resulting in a discharge of the capaci tor 3 through the primary winding 9 and valve that time the rectifier valve | I9 becomes conduc tive causing the second firing valve 99 to render 29|. the shunt connected valve 81 conductive. The 15 As vpreviously mentioned, the capacitor 3 is charge the capacitor 3 inversely. However, at shunt connected valve 81 then conducts the en tire current resulting from the release of stored energy so that the series connected valve 61 be comes 'non-conductive. At that instant the pentode |49 also becomes non-conductive and re originally charged with one plate 4| positive and the other plate 43 negative. When the capacitor 3 is discharged, the discharge current flowing through the primary winding 9 stores energy in the welding transformer and the secondary cir charging of the capacitor 3 is initiated. After the capacitor 3 is discharged, the commu cuit. As the discharge of the capacitor is com pleted, the energy so stored is released causing the tator l 61 opens the circuit through the coil |63 of capacitor to be charged inversely with plate 43 positive and plate 4I negative. The anode 221 of the solenoid valve |65 `permitting the piston |83 to be moved to open the contactor |85 in the ñring circuit of the first firing valve 69 and permitting the electrode I5 to be moved out of engagement with the work i9 so that the work may be repo the second valve 293 is connected to the plate 49 while its cathode 2.29 is connected through the primary winding 9 and resistor 6| to the plate 4|. Consequently, if the second valve 293 is then sitioned for a new weld. After a time interval rendered conductive, the inverse charge on the suiiicient foi` the capacitor 3 to be recharged the 20 capacitor 3 is discharged through the valve 293, the primary winding 9 and resistor 6|. commutator |61 again completes the circuit through the operating coil |23 of the solenoid Another electric discharge valve 23| of the valve | 55 and another weld is initiated. arc-like type, preferably a thyratron, and also In Fig. 2 is illustrated a similar blocking circuit as applied to a different kind of capacitor dis- 1, charge welder. This Welder is known as the full cycle welder and is disclosed and claimed in the copending application of Ezra T. Hughes and Stephen vL. Burgwin, Serial No. 511,575, filed November 2li, 1943. Here, the capacitor 3 is again charged from an alternating current source 5 through the same kind of a charging circuit 1 as was described in connection with Fig. 1 and the same reference characters are employed to desig designated as a firing valve, is connected in series with a current limiting resistor 233 between the anode 221 and the ignition electrode 235 of the second valve 203. The grid 231 of firing valve 23| is connected through a grid resistor 239 to the cathode 24| of the firing valve. Consequent ly, when the resultant potential in the circuit consisting of the capacitor 3, the primary wind ing 9, resistor 5| and the valves 29| and 293, has the opposite polarity from the original charge on the capacitor, the firing valve 23| becomes 45 conductive to render the second valve 293 con ductive. An auxiliary transformer |25 is also provided nected through the small resistor 6| to one side with its primary winding |21 connected across 59 of the primary winding 9 of the welding trans the small resistor 6| in the discharge circuit of former Il. The other side 51 of the primary winding e is connected to the other plate t3 of 50 the capacitor 3 and its secondary winding |29 the capacitor 3 through a pair of inversely con connected to supply a control voltage for the nate corresponding elements. The positive `plate 4| of the capacitor 3 is con nected valves 20| and 253, preferably ignitrons. pentode ampliñer tube |119, the output circuit of which is arranged to develop a potential across the resistor 55 to prevent operation of the charg nected to the negative plate 43 of the capacitor 3 and the anode 291 is connected to the positive 55 ing circuit 1 while the pentode |119 is conductive. plate ¿il through the primary winding 9 and re This blocking circuit is similar to the one de scribed in connection with Fig. 1 but in addition sistor 5|. a full wave rectifier 2133 is interposed between An electric discharge valve 299 of the arc-like the secondary winding |29 of the auxiliary trans type,v preferably a thyratron, which is herein after designated as a firing valve, is connected in 80. former |25 and the resistor löl. This full wave rectifier 243 is necessary in this circuit because series with a current limiting resistor 2| | between current ñows through the resistor 6| in both the anode 291 and ignition electrode 2|3 of the directions during the discharging operations of first valve 29|. When the firing valve 209 is ren the capacitor 3. Another capacitor 245 is also dered conductive, current starts to iiow in the circuit extending from the positive `plate 4| of 65 connected across the resistor 55 in the output circuit of the pentode |29 to prevent too rapid a the capacitor 3 through the resistor 6|, the «pri response to a decrease in potential across the mary winding 9, the current limiting resistor 2| |, resistor 5 l. In this way the momentary decrease the firing valve 299, the ignition electrode 2| 3 in voltage across the resistor 6| as the current and cathode 295 of the first valve 29| to the other plate 43 of the capacitor. This ignition current 70 therethrough passes through zero during the dis charging operation does not affect the blocking renders the first valve 29| conductive and the of the charging circuit 1. main discharge of the capacitor 3 through the primary winding 9 and the first valve 29| is A flux resetting circuit 241 is provided for rea effected. ` sons set forth in the aforesaid Hughes and The control circuit of the firing valve 299 may 75 _Burgwin application. This circuit effects a flow The cathode 205 of the first valve 29| is con _2,404,971 T9. 1'0 of- direct current through a portion'l -of the pri departure from the inventive concept- here dis closed. We do not intend, therefore, to limit our invention to the specific embodiments described and illustrated. mary winding 9 as long as contactor 249 is closed. Contactor 249 is operated by pressure responsive 'piston |83 and is open during Welding operations and closed between successive operations. We claim as our invention: When the circuit breaker 2| in Fig. 2 is first 1. Apparatus for use in supplying current to a closed, the capacitor 3 is charged in the usual load comprising a capacitor, charging means con manner to the preselected voltage. To initiate nected across said capacitor and tending to sup a Welding ‘operation the hand switch |6| is then ply- current therethrough to charge the same closed `causing the hydraulic system to move elec 10 whenever the capacitor voltage is below a prede trodes I5 and l1 into engagement with the mate termined value, circuit means connecting said ca rial I9 when commutator |61 completes the cir pacitor across said load to eiiect discharge of- said cuit. The hydraulic system moves piston |83 to capacitor therethrough, said circuit means in the left, opening contactor 249 to open the flux cluding valve means interposed between said _ca resetting circuit 241 and closing a second con pacitor and load for controlling the fiow of cur tactor 25| to complete al circuit from the source rent therebetween and impedance means in series through the coil 253 of a relay 255. The con with said valve means ¿whereby a voltage is devel tactor 251 on the relay 255 in its deenergized oped across said impedance means in response to position completes a charging circuit for an auX current conducted through said valve means, iliary capacitor 259 from a direct current source means responsive to said voltage and connected to 26|. When the relay 255 is energized, the charg said charging means for preventing operation of ing circuit is opened and the contactor 251 closes said charging means only during current'flow a discharge circuit for the capacitor 259 through through said valve means, and control means the primarywinding 253 of the peaking trans connected to said valve means to cause said valve former 22|, the secondary winding of which is 25 means to be conductive during each of a plural in the control circuit of the first firing valve ity of spaced intervals. 209. As a result the first valve 20| is rendered 2. Apparatus for use in supplying current to a conductive and the main capacitor 3 is discharged load comprising a capacitor, charging means con through the primary winding 9 of the weldin nected across said capacitor and tending to sup transformer ||. The capacitor 3 thereafter re-v 30 ply current therethrough to charge the same ceives an inverse charge before the current Whenever the capacitor voltage is below a prede through the first valve 20| drops to zero. At that termined value, circuit means connecting said ca-time the second valve 203 is rendered conductive pacitor across said load to eiiect discharge of said and the inverse charge on the capacitor 3 is dis capacitor therethrough, said circuit means in charged back through the primary winding 9. cluding valve means interposed between said ca During the period of conductivity of the first and pacitor and load for controlling the iiow of cur second valves 20| and 203, current is ñowing rent therebetween and a resistor in series with through the resistor 6I in series therewith which said valve means through which passes only the acts through the auxiliary transformer |25 and current conducted through said valve means, con the pentode |49 to prevent operation of the 40 trol means connected to said valve means to cause charging circuit 'I for the main capacitor 3,. As said valve means to be conductive during each of soon as the second valve 203 becomes non-con a plurality of spaced intervals, and means con ductive the blocking potential on the charging nected to said resistor and to said charging means circuit 'l is removed and recharging of the capaci and responsive to the potential developed across tor 3 by the charging circuit is initiated. said resistor by a flow of current therethrough to It is to be noted that while the initial dis prevent operation of said charging means only charge of the capacitor 3 through the first valve during such current flow. ~ 20| is sufficient to produce a weld, the subse >3. Apparatus forv use in supplying current to a ‘quent discharge of the inverse charge on the load comprising a capacitor, charging >means con capacitor is not sufficient to eiîect welding. The nected across said capacitor and tending to sup discharge of the inverse charge on the capacitor ply- current therethrough to charge the same does, however, act to return the ñuX of the whenever the capacitor potential is -below a pre welding transformer a considerable way toward determined value, circuit means connecting said its original state. enabling the welding electrodes capacitor across said load to eiiect dischargeof to be opened immediately thereafter without said capacitor therethrough, said circuit means danger of arcing at the tips of the electrodes. including valve means interposed between said Moreover, the portion of the inverse charge which capacitor and load for controlling the iiow of cur is not employed in resetting the flux is again rent therebetween and a resistor in series with stored in the capacitor with the originalpolarity said valve means through which passes only the so that it is not wasted. The many advantages 60 current conductedV through said valve means, of such full cycle operation is fully set forth control means connected to said valve means to in the aforementioned copendlng application of cause said valve means to be conductive during Hughes and Burgwin. each of a plurality of spaced intervals, a trans Following the discharging operation the com former having a primary and a secondary Wind mutator |61 opens the circuit through the sole ing with the primary winding connected in cir noid valve |65 causing the electrodes I5 and l1 cuit across said resistor, said transformer being to be opened, the flux resetting circuit to be of the type in which the wave-form of the voltage reclosed and the relay 255 to be deenergized. across the secondary winding is substantially the After a time period during which the capacitors 3 and 259 are recharged, the commutator again 70 same as that of the voltage across the primary winding, and means connected to said secondary completes the circuit through the solenoid valve winding for preventing operation of said charging and another welding operation is initiated. means only while said valve means is conductive and in response to the voltage developed across said resistor by a flow of current therethrough. that modifications thereof may be made without 75 4. Apparatus for use in supplying current to a Although we have shown and described a spe ciflc embodiment of our invention, we are aware 2,404,971 ll load comprising a capacitor, charging means con nected across said capacitor and tending to sup ply current therethrough to charge the same whenever the capacitor potential is below a pre determined value, circuit means connecting said capacitor across said load to effect discharge of said capacitor therethrough, said circuit means including valve means interposed between said capacitor and load for controlling the flow of cur rent therebetween and a resistor in series with said valve means through which passes only the current conducted through said valve means, con trol means connected to said valve means to Cause said valve means to be conductive during each of a plurality of spaced intervals, a transformer having a primary and a secondary winding with the primary winding connected in circuit across said resistor, said transformer being of the type in ' which the wave-form of the voltage across the secondary winding is the same as that of the volt~ age across the primary winding, said charging means including second control means respon sive to the impressing thereon of a direct current voltage of a predetermined polarity and minimum 12 load through a magnetic core transformer having primary and second windings with said secondary winding being connected in circuit with said load, comprising a capacitor, means connected across said capacitor to supply charging current there through whenever the capacitor potential is be low a predetermined value, means including nor mally non-cc-nductive valve means connecting said capacitor in circuit across said primary winding whereby an oscillating current tends to flow through said primary winding when said valve means is conductive, control means con nected to said valve means for rendering the same conductive at spaced intervals to permit a full cycle of oscillating current to flow' through said primary winding, impedance means in series with said valve means whereby a voltage is devel ope-d across said impedance means by current conducted through said valve means, and means responsive to said voltage and connected to said _charging means for preventing operation of said charging means only while valve means is con ductive. '7'. Apparatus for use in supplying current to a magnitude to prevent operation of said charging 25 load through a magnetic core transformer having primary and secondary windings with said sec ondary winding being connected in circuit with an input circuit supplied from said secondary said load, comprising a capacitor, means connect winding for impressing a direct current voltage ed across said capacitor to supply charging cur of at least said predetermined minimum magni tude and of said polarity on said second control 30 rent therethrough whenever the capacitor poten~ tial is below a predetermined value, means includ means throughout substantially the entire inter ing normally non-conductive valve means con val of current iiow through said resistor. necting said capacitor in circuit across said pri 5. Apparatus for use in supplying current to an mary 'winding' whereby an oscillating current inductive load comprising a capacitor, charging tends to now through said primary winding when means connected across said capacitor and tend 'said valve means is conductive, control means ing to supply current therethrough to charge the connected to said valve means for rendering the same with a predetermined polarity whenever the same conductive at spaced intervals to permit a capacitor potential is below a preselected value, single _cycle of oscillating current to flow through circuit means connecting said capacitor across ~said primary winding, a resistor in series with said said load including a iirst electric discharge valve valve means, a second transformer having a pri of the arc-like type interposed between said ca mary and a secondary winding with the primary pa'citor and load for controlling the discharge of winding connected in circuit across said resistor, 'said capacitor through said load, control means said second transformer being of the type in connected to said ñrst valve to render it con which the wave form of the voltage across the ductive at spaced intervals, a second electric dis secondary winding is the same as that of the prie charge valve of the arc-like type connected in mary winding voltage, said charging means in parallel circuit relation to said capacitor and iirst cluding Second control means responsive to the valve, and means connected to said second valve impressing thereon of a direct current voltage ci and to said load to render said second valve con ductive following each discharge of said capacitor 50 a predetermined minimum magnitude and polar ity to prevent operation o'f said charging means, to conduct current resulting from a release of and means including a rectifier connected across the energy stored in said load during the dis-4 the secondary winding of said second transformer charge, said circuit means also including imped and an ampliñer supplied from said rectifier for ance means in series with said ñrst valve and said parallel connected second valve and load whereby f ’ impressing a direct current voltage of at least means, and means including an ampliiier having a voltage is developed across said impedance means by current passing though said ñrst valve, and means responsive to said voltage and con nected to said charging means to prevent opera tion thereof only while said Voltage is present. 6. Apparatus for use in supplying current to a said predetermined minimum magnitude and said polarity on said control means throughout substantially all said single cycle of oscillating current. JOI-IN R. MAHONEY. HARRY J. BICHSEL.