US2874314A

US2874314A - Electrical timing apparatus

Info

Publication number: US2874314A
Application number: US653683A
Authority: US
Inventors: Roy W Shipman
Original assignee: Weltronic Co
Current assignee: Weltronic Co
Priority date: 1953-12-07
Filing date: 1957-04-18
Publication date: 1959-02-17
Anticipated expiration: 1976-02-17

Description

Feb. 17 1959 R. w. SHIPMAN 2,874,314

ELECTRICAL TIMING APPARATUS Original Filed Dec. 7, 1953 2 Sheets-Sheet 1 INf ENTOR. F0; 14. 5177/7141,

I Feb. 17, 1959 Original Filed Dec. 7. 1953 R. w. SHIPMAN ELECTRICAL TIMING APPARATUS United States Patent ELECTRICAL TIMING APPARATUS Roy W. Shipman, Detroit, Mich., assignor to Weltronic Company, Detroit, Mich., a corporation of Michigan Original application December 7, 1953, Serial No. 396,585. Divided and this application April 18, 1957, Serial No. 653,683

14 Claims. (Cl. 307--ll06) This invention relates generally to electrical timing apparatus which is particularly adapted, among other uses, as a sequence timer for a resistance welding apparatus.

. An object of this invention is to provide a new and improved timing network.

A further object of this invention is to provide such a network in which a pair of timing networks are concurrently charged and thereafter perform their timing functions in succession.

Another object of this invention is to provide in such a network a new and improved pulsing circuit for con trolling the instant in the half cycle of the supplied potential at which certain of the network valves may be rendered conducting. 6

Another object of this invention is to provide a new and improved interrelation between the energy flow controlling valves and the valve controlling the termination of the energy flow period.

Another object of this invention is to provide a new and improved circuit for controlling the network for providing a series of repeating operations thereof or for providing single operation thereof in response to actuation of the initiating switch.

Other objects of this invention will be apparent from the specification, the appended claims, and the drawings, in which drawings:

Figures 1A and 1B schematically illustrate a preferred form of timing network embodying the invention;

Fig. 2 illustrates the operation of the pulsing circuit sub-combination; and,

- Fig. 3 illustrates a modified form of pulsing circuit.

This application is a division of my copending application Serial No. 396,585 filed December 7, 1953, for Electrical Timing Apparatus.

The invention is illustrated in a sequencing network 1 for performing the standard NEMA 5B type functions which are Squeeze Time, Weld Interval Time, Cool Time, Heat Time, Hold Time, and Off Time. Alternating potential for actuating the network 1 is supplied from a transformer T1 having its primary winding 2 connectible with a suitable source of alternating potential, as for example, a 440 volt 60 cycle supply, by means of the line switch LS1. One terminal 4 of the secondary winding 6 of the transformer T1 is continually connected to a bus B1 and selectively connected to a bus B2 by means of the start switch SW1 and the contacts CRlb of a relay CR1. The other terminal 8 of the winding 6 is continually connected to the bus B3.

A squeeze time network 10 controls the time interval between the closure of the start switch SW1 and the initiation of conduction of thyratron 1V. A weld interval timing network 12 controls the time interval between the time that thyratron 1V conducts and the conduction of thyratrons 2V and 3V to terminate the weld interval period. A hold time" network 14 controls the time interval between the initiation of conduction of the thyratrons 2V and 3V and the conduction of thyratron 4V to terminate the hold time period. This between the initiation of conduction of the thyratron 4V and the re-initiation of the thyratron 5V to start a subsequent operation.

The heat and cool time periods are controlled by a multivibrator network 18 including the heat time controlling network 20 and the cool time controlling network 22 which control the rate at which the thyratrons 6V and 7V alternately conduct during the weld time interval. During the nonconducting time period of thyratron 6V (conducting time period of thyratron 7V) the back-to-back or reversedly connected thyratrons 8V and 9V will conduct each cycle of the voltage supplied through the line switch LS1 to energize the transformer T7. When energized, transformer T7 overrides the blocking bias applied to the firing thyratrons 10V and 11V respectively whereby they conduct to fire the ignitrons 12V and 13V. When conductive, the ignitrons 12V and 13V energize the welding transformer T3 to supply energy to the welding electrodes E. Closure of the switch SW5 will reduce the weld time interval below the heat time interval and the network will provide only a single heat interval as determined by the network 20.

In the present embodiment, the anode of the thyratron 1V is connected through normally open contacts CRZa of the control relay CR2, a single-repeat switch SW2 (shown in open or repeat position), an emergency stop switch SW3, to the bus B2. The common terminal 24 of the switches SW2 and SW3 is connected through the energizing winding 26 of the control relay CR1 to the anode of the thyratron 5V, the cathode of which is connected to the bus B3. The anode of the thyratron 1V is also connected through the energizing winding 28 of the control relay CR2 to the bus B3 while the cathode of the thyratron 1V is continually connected to the bus B3 through a resistor R1 and selectively connected to the bus B2 through the normally open contacts CRIc of the relay CR1.

One terminal'30 of the squeeze time network 10 is connected through the usual current limiting resistor to the control grid of the thyratron 1V and the other terminal 32 thereof is connected to a common terminal 34 intermediate a pair of series connected resistors R2 and R3. The free terminal of the resistor R2 is connected to the bus B1 while the free terminal of the resistor R3 is connected through a resistor-capacitor network 36 and a resistor R4 to the bus B3. When the contacts CRlc are open, the potential of the cathode of thyratron 1V is substantially that of the bus B3 and the network 10 charged by grid conduction of the thyratron 1V. When contacts CRlc close, the potential of this cathode is made that of bus B2 and the potential appearing across the network 10 as Well as that appearing across the resistor R2 is applied between the control grid and cathode of thyratron IV. The resistor R2 superimposes a relatively low magnitude A. C. component on the blocking potential established by the network 10 to provide more accuracy to the squeeze timing function. Also the potential across resistor R2, when acting alone, will provide a firing potential to insure that an otherwise slow-to-fire tube conducts when desired.

The anode of the thyratron 4V is connected to bus B3 through a conductor 38, the off time network 16 and resistor R4. The conductor 38 connects with one terminal 40 of the off time" network 16 and the other terminal 42-of this network is connected to terminal 44 I which is intermediate the resistor R4 and the network 36. The cathode of thyratron 4V is connected through the anode-cathode circuit of thyratron 2V and contacts CRZc to bus B2 and can only conduct when the thyratron 2V is conducting. The control grid of this thyratron is connected through a grid current limiting resistor, network 1'4'and resistors R3 and R4 to bus B1. The potential appearing across the resistors R2 and R3 pro-' vide an-alternating control potential superimposed upon the potential established by the hold time network 14 for controlling the delay between the firing of thyratron 2V and the firing of the thyratron 4V. Likewise, the potential appearing across the resistor R4 provides an altern'ntingpotential superimposed-upon that of the off time network 16 for controlling the thyratron 5V.

The thyratrons 2V and 3V 'are'c'onnected in back-toback or anti-parallel relationship between the busse's B2 and B3through the nansrormer T4. More particularly, the anode of thyratron 2V and the cathode of thyratron 3V are connected through a resistor-capacitor network 46 and the primarywinding 48 of the transformer T4 tothe bus B3 while the anode of the thyratron 3V and cathode of the'thyr'atron 2Vare connected through the normally open contacts CR2c to the bus B2. The con-. trol grid of the thyratron 2V is connected through the weld interval timing network 12 to the terminal 34 and serves to controlthe time interval between the closure of contacts CR2c and the firing of thyratron 2V.

The control grid of the thyratron 3V is connected through resistors R5 and R6 and network 46 to the cathride of the thyratron 3V. An alternating biasing potentrial is normally applied across the resistor R6 by means of the transformer T5 having its primary winding connected between the busses B1 and B3. The phasing of the potential supplied by the transformer T5 with respect to that applied between the anode and cathode of the thyratron 3V is "such that whenever this anode is positive with respect to this cathode and the network 46 is deenergize'd a negative grid-to-cathode potential will be maintained across the resistor R6. When, however, the thyratron 2V conducts during the half cycle preceding the half cycle in which the anode of thyratron 3V is positive WlihlSPeCt to its cathode, the network 46 will be energ'i'zed and the potential established thereacross will overcome that established across the resistor R6 and the thyratron 3V will conduct each half cycle subsequent to the half cycle in which the thyratron 2V conducts.

The transformer T4 has a center tapped secondary winding 51, the end terminals of which are connected through'rectifiers 53 to the negative terminal '52 of the resistor R7. The centcr tap connection is connected to tfi'positive ter'minal 54 of resistor R7. One terminal 52 o'ffthe resistor R7 is connected through the usual gr d current limiting resistor to the shield grid of the thyratfon7V and the other terminal 54 thereof is connected'through the resistors R8 and R9 to the common cathode connection 56 of the thyratrons 6V and 7V. Therefore when transformer T4 is energized, its rectified output establishes a blocking bias potential across the resistor R7 whichovercomes the conducting potential peaks which are otherwise supplied to thyratron 7V by the resistors R8 and R9. The shield grid to cathode circuit of the thyratron 6V does not include the resistor R7 and is uninfluenced by theenergization of the transformer T4. The :grid is connected through the usual current limiting resistor and theresistors R8 and R9 to the common cathode connection "56 whereby this grid willbe brought to "a conducting bias once-each alternate half cycle of the voltage applied through the'switch LS1. The anode of the thyratron 7V is connected to the positive-bus Bthro'ugh the normally open contact CR2d and resistorsR-10, R-ll,and R12 and the anode of thyratron ;6V is connected to this bus through resistors R14 and R15. The cathodes of these thyratrons, are connectedto' a common cathode connection 56.

The positive bus B4 and cathode connection 56 are energized by rectifying the output of the transformer T6. More specifically, bus B4 is connected to the end terminals 58 and 66 of the secondary winding 62 of transformer T6 through the

rectifiers

64 and 66, resistor R13 and capacitors C1 and C2. The center tapped terminal 68 of the winding 62 is connected by conductor 70 and branch conductor 72 to the common cathode connection 56. Capacitors C1 and C2 which are connected in series relation in shunt with the resistor R13 stabilize the direct current potential between the bus B4 and the cathode connection 56.

A commutating capacitor C3 is connected between the anodes of the thyratrons 6V and 7V to proviide for a momentary change in anode-cathode potential of the conducting one of the thyratrons 6V or 7V upon the initiation of conduction of the other thereof to extinguish the previously conducting thyratron upon conduction of the otherthereof as is well known'in the art.

The air of timing networks 29 and22 hold the thyratrons 6V and 7V'respetcively blocked "fora'predtermincd time intervalcssubsequent to conduction of the other thereof. The network 22 comprises a capacitor C4 hav ing a discharge circuit which includes the variable rcsistor R16, resistor R17, and resistor R18. 'During standby periods of the network 1, the normally closed contacts CRld are closed and shunt out the variable resistor. R16 to insure a rapid discharge of the capacitor C4. During operation of the network 1, however, the contacts CRld remain open and the rate of discharge of the capacitor C4 will be primarily controlledby the setting of the resistor R16. One terminal 74 of thempacitor C4 is connected to the bus Be'through the series connected resistors'Rl and R15 connected in parallel with the series connected resistors Ri and RIQ. The other terminal 76 of the capacitor "C4 is connected 7 through a current limiting resistor to thegrid of the thyratron 7V. 'During the nonconducting period of the thyratron 6V, the potential of terminal 74 will be substantially that of the positive bus B4 and'the capacitor C4 will charge'dueto the flow of grid current through the thyratron 7V. Upon conduction of the thyratron 7V, the terminal 74 (which is then positive with respect to the terminal '76) is connected through thethyratron 6V to the common cathode connection 56 to place a blocking bias potential between 'the grid and cathode of the thyratron 7V to maintain 'this'thyratron'blocked until the capacitor C4 has discharged to a predetermined'low value, after which the thyratron 7V will be rendered conducting 'at an instant determined by the potential across the resistorsRe andR'Si (to be more clearly set out below) provided, however, that 'thctransforrner T4 is not energized.

The heat time" network 20 comprises the capacitor C5 having one terminal 78 connected through the series connected resistors R10, R11, and R12 to the bus B4 having in parallel therewith the series connected resistors R20 and R21. The other terminal 80 is connected through a grid current limiting resistor to the control grid of thyratron W. A discharge circuit for the capacitorCS extends from terminal tltl through variable resistor R22 and resistorRZtl to the other terminal 78. With this arrangement, the capacitor C5 will be charged by grid current flow of the thyratron 6V during the periodsin which .the thyratron 7V is blocked but when thethyratron 7V conducts, the terminal '78 is eifectively connected to the common cathode connection '56 andthe capacitor US will provide a blocking bias potential hetween the grid and cathode of thyratron 6V for a'time period primarily dependent upon the magnitude of the resistorRZZ. The blocked period of the thyratron 6V, as will be hereinafter set forth,'determines'thextime period-in which'the transformer T3 isenergized'to'supply welding potential to the electrodesE. .The .blocked .or

' nonconduc'ting time period vofithe thyratron 7V likewise determines the cool time" period or intervening interval in which the transformer T3 is not energized to supply potential to the welding electrodes E.

It should be noted that the resistor R11 is connected in series between the shield grid and cathode of the thyratron 2V. The direction of the potential established thereacross, when the thyratron 7V conducts (indicating the occurrence of a heat period), is such as to establish a blocking bias between the shield grid and cathode of the thyratron 2V and prevents thyratron 2V from conducting during a heat period even though the weld interval timing network 12 times out. This interrelationship between the thyratrons 2V and 7V insures a complete heat period each time that the electrodes E are energized.

In standby condition, the contacts CR2d will be open to interrupt the anode circuit of the thyratron 7V and the thyratron 6V will continually conduct. The continual conduction of thyratron 6V maintains a potential across the resistor R15 which is applied as a blocking bias potential between the grid and cathode of the thyratron 8V to keep this thyratron blocked. More specifically, the

grid of the thyratron 8V is connected through the usual current limiting resistor to the common terminal 82 of the resistors R14 and R15 while the cathode thereof is connected through the bus B2 to the common terminal 84 between the resistors R11 and R12. The grid-cathode circuit is completed through the resistor R12 and bus B4 to the other or upper terminal of the resistor R15. When thyratron 6V conducts, thyratron 7V will be blocked and the potential appearing across resistor R15 will block the thyratron 8V. When, however, the thyratron 6V blocks and the thyratron'7V conducts, the potential across the resistor R12 will act to apply a conducting bias between the grid and cathode of the thyratron 8V to insure that it conducts.

The thyratrons 8V and 9V are connected in anti-parallel relationship with each other. and in series with the primary winding 88 of a transformer T7 between the busses B2 and B3 through a resistor-capacitor network 86, and a weld-no-weld switch SW4. It will be recognized that the grid-cathode circuit for the thyratron 9V is similar to that explained above in connection with the thyratron 3V so that the thyratron 9V trails the conduction of thyratron 8V and unless the thyratron 8V conducts the thyratron 9V will remain blocked.

The transformer T7 is provided with secondary windings 90 and 92. The winding 90 is connected between the grid and cathode of the firing thyratron 10V through a biasing network 94 while the winding 92 is connected between the grid and cathode of the firing thyratron 11V through a biasing network 96. The networks 94 and 96 maintain the firing thyratrons 10V and 11V blocked so long as the transformer T7 remains deenergized. The potential established by the windings 90 and 92, with the transformer T7 energized, is of such magnitude and phase .as to overcome the blocking bias established by the net- .works 94 and 96 to cause the firing thyratrons 10V and 11V to conduct during the half cycles in which their respective anodes are positive with respect to their cathodes. When conducting, the thyratrons 10V and 11V trigger the ignitrons 12V and 13V respectively in a manner well known in the art.

The transformer T3 may be of the Hipersil type or may be power factor corrected by use of a series capacitor and the network 98 containing the resistors R8 and R9 is arranged to provide for firing the thyratrons 6V and 7V at av predetermined point in the voltage wave applied between the main busses B5 and B6. The transformer T3 is connected in series with the back-to-back ignitrons 12V and 13V between these busses B5 and B6.

The particular phase angle at which the thyratron 7V will conduct is controlled by means of the phase-shifting network 100. This network, as illustrated, is of the usual type in which a resistor R24 and a capacitor C6 are series connected between the end terminals 58 and 60 of a center tapped transformer winding 62, and degree of phase shift imparted to the potential appearing between the

terminals

68 and 102 thereof is controlled by the relative magnitudes of the resistor R24 and capacitor C6. The conductor 70 connects the center tap 68 with one terminal 104 of the primary winding 106 of transformer T8. The other terminal 108 of this winding is connected by conductor 110 to-the terminal 102. At present it seems preferable to arrange the values of resistor R24 and capacitor C6 to provide for firing the thyratron 7V at substantially the point in the half cycle of voltage in which the bus B5 is positive with respect to the bus B6, and for this purpose the network is adjusted to phase shift the voltage applied to the winding 106 so that it lags the voltage between the bosses B5 and B6 by 90. The transformer T8 is provided with a center tapped secondary winding 112 having a center tap 114 and end terminals 116 and 118. The common terminal 120 of the resistors R8 and R9 is connected to the center tap 114. The other terminal 122 of the resistor R8 is connected through a capacitor C7 to the terminal 116 while the other terminal 124 of the resistor R9 is connected through a rectifier 126 to the terminal 118. The terminal 116 is connected through rectifier 128 to the terminal 124. This arrangement provides a direct current pulsating voltage across the resistor R9 which pulsates once each half cycle of the voltage appearing between the busses B5 and B6. An alternating voltage will appear across the resistor R8 which is phase shifted from that appearing across the winding 112 by an amount depending upon the relative magnitudes of the resistor R8 and capacitor C7 and in this instance is 90 degrees leading. The potential applied between the bussesB'e' and B6 is represented in Fig. 2(a) by the line E1. The phase shifted output potential of the network 100 is represented in Fig. 2(b) by the line Eps. The rectified pulsating potential appearing across the resistor R9 is represented in Fig. 2(c) by the line Er9. The phase shift alternating potential appearing across the resistor R8 is illustrated in Fig. 2(a') by the line Er8. The wave Eg in Fig. 2(e) illustrates the potential appearing between the

terminals

124 and 122, which is applied between the shield grid and cathode of the thyratron 6V. The potential wave Eg will be applied between the shield grid and cathode of the thyratron 7V but during the period in which the transformer T4 is energized this will be lowered with respect to the horizontal zero line so that the high peaks of the wave Eg will not be of sufiicient magnitude to render the thyratron 7V conducting. From a study of Fig. 2 it will be apparent that by phase shifting the output voltage of the phase-shift network 100, the peaks of wave Eg may be made to occur at any desired interval in the voltage wave E1.

In Fig. 3 there is shown a modified form of peaking network 98a which may be used to provide the same wave shape Eg, Fig. 2(a), which is provided by the networks 98 and 100. This network eliminates the need for phase shifting the voltage applied to the transformer T811 and the primary winding 106a thereof may be connected directly to the potential supplying busses B5a and 136a. The transformer T8a is provided with a first secondary winding 130 having output terminals 132 and 134. Connected between the terminals 132 and 134 are a pair of circuits each containing a resistor and a capacitor. The resistor R26 has its free terminal connected to the terminal 132 and the free terminal of its associated capacitor C8 is connected to the terminal 134. The resistor R27 of the other circuit has its free terminal connected to the terminal 134 while the free terminal of its associated capacitor C9 is connected to the terminal 132. The common connection 135 between the capacitor C9 and resistor R27 of the phase circuit is connected to the common connection 133 between the resistor R26 and capacitor C8 by a pair of resistors R28 and R29. The

'7 resistor R28 has connected .in series circuit therewith, a rectifier 136 while the resistor R29 has connected in series circuit therewith a rectifier 138. The rectifier 136 is connected to conduct current in a direction opposite to the direction in which the rectifier 138 conducts.

The common terminal 140 between the rectifier 136 and resistor R28 is connected through a second secondary winding 142 of the transformer T8a to the terminal 150 connected to the cathode of a thyratron 14V while the common terminal 144 of the resistor R29 and rectifier 138 is connected through a resistor R39, rectifier 148 and normally open switch SW to the terminal 159. A timing network 146 and current limitingresistor .is connected between the grid of the thyratron 14V and terminal 152 of rectifier 143. By proper selection of the values of the resistor R27 and capacitor C9, zandthe relative values of the resistor R26 and capacitor (28, the potential appearing across the resistors R28andR29 may becmade to correspondto the voltage wave .Eps, Fig. 2(1)), when the voltage supplied by the winding .13!) corresponds to the wave E1, Fig. 2(a). The voltage appearing across the'resis'tor R23 corresponds to alternate ones of the loops Er9, Fig. 2(a), while the voltage-appearing across the resistor R29 corresponds to the intervening loops ofthe curve Er9. The potential supplied by the winding 142 corresponds to the potential wave ErS, Fig. 2(d). When theseare combined together, the summation will correspond to the curve Eg, Fig. 2(a), and this wave is applied to the rectifier 148. The rectifier 148 is polarized to permit substantially unimpeded conduction of the portion of the wave Eg appearing below the zero axis thereof but imposes a high impedance to the flow of the portion of the wave which appears above the zero line. The potential appearing acrossthe rectifier 148 is represented by the voltage pips Ega as shown in Fig. 2(f). It will be apparent that the voltage appearing across the rectifier 148 is added to that appearing across the timing network 146 and the potential placed between the grid and cathode of the thyratron 14V is in the form of a capacitor discharge curve in which there is superimposed the voltage pips Egzz. The magnitude of these pips Ega is so chosen with respect to that of the discharge curve of the network 146 that the thyratron 14V will be rendered conducting in the half cycle of the voltage in which the bus 35a is positive with respect to the bus 136a at an instant determined by the occurrence of the voltage'pips Ega.

It is believed that the remaining details of construction may best be understood by a description of operation of the apparatus, which is as follows:

In normal standby condition, the line switch LS1 .is

' closed energizing the. bosses BS and B6 and the transformer T1. When energized, the transformer T1 energizes the busses B1 and B3 to supply energizing potential for charging the squeeze time network 10, the weld interval timing network 12,- and the hold time .network 14. Energization of the busses B1 and B3 also energize the blocking bias producing transformers T5 and T2 for the thyratrons 3V and 9V respectively and the transformer T6 which supplies the direct potential between the bus as and connection. 56. With the transformer T6 energized, the network 98 will beenergized and the thyratron 6V will conduct. It will further be appreciated that all of the anode-cathode circuits for the valves TV through 9V except 6V and 7! are connected of the relay CR1, all of these thyratrons, therefore, are

in a normally nonconducting condition. Thyratron 7V cannot conduct since its anode circuit is open through contacts CRZd. The firing thyratrons 10V and 11V while .having their anode circuits connected hetween'zthe 8 firing the ignitrons 12V and 13V by the blocking bias establishing networks '94 and '96.

When it is desired to initiate a weld, the switch SW1 is closed to connect the bus .B2 to the terminal 4 of the transformer T1. This establishes a potential between busses B2 and B3 and current then flows through the winding 26 of the relay CR1 through the thyratron 5V in a circuit which extends from the bus B2 through the normally closed emergency stop switch SW3, winding 26, anode to cathode of the thyratron 5V to the bus B3. Upon energization, the relay CR1 closes its contacts CRla to complete a circuit for the usual ram mechanism (not shown) .for moving the electrodes .13 against the workpiece W. Closure of the contacts CRlb completes a holding circuit about the switch SW1 which may'now beopened without interfering with the cycle then in process. In repeating operatiomthe switchSWl will be held closed until the desired number of weld spots have been initiated. Closure of the contacts CRlc completes the circuit from the cathode of 'the'thyratron 1V to the bus B2 thereby completing the biasing circuit through the squeeze time network 10 and the resistor R2 for the thyratron IV. This closure of the contacts CRlc also effectively transfers the potential of the cathode of the thyratron 1V from that of the bus B3 to that of the bus B2 thereby terminating further charging of the squeeze time network 10 and permitting it to discharge. Opening of the contacts CRld opens the shunt circuit-about the resistor R16 of the cool time network .22.

At the end of a predetermined squeeze time interval as determined by. the rate of discharge of the network 10, the thyratron 1V conducts to complete a circuit between the busses B3 and B2 through the energizing winding 28 of the relay'CR2, the anode-cathode of the thyratron 1V, and the now closed contacts CRlc. Upon encrgization, the relay CR2 closes its contacts CR2'a without effect since it is now assumed that the single-repeat switch SW2 is in its open position for repeat operation.

Closure of the contacts CR2c completes the anode-cathode circuits for the thyratrons 2V and 3V between the busses B2 and B3 and completes the grid to cathodebias ing circuit for the thyratron 2V whereby the potential established across the Weld interval timing'network 12 is applied as a biasing potential between the grid and cathode. This also terminates further charging of the network 12 to permit it to discharge to time the weld interval. Opening of the contacts CR2b opens the circuitthrough resistor R31 to line B3 and reduces the current which would otherwise be drawn thereby were the connection maintained. Closure of the contacts CRZ d completes the anode circuit for the thyratron 7V which thereupon commences to conduct and blow outthe thyratron 6V at the next peak Eg. This results in energizetion of the resistor R12 and deenergization of the resistor R15 to remove the blocking bias from and to provide a conducting bias potential between the grid and cathode of the thyratron 8V. Thyratron 8V thereupon fires and thyratron 9V trails to energize the transformer T7 which overcomes the blocking bias potential on the firing thyratrons 10V and 11V'which fire to fire the ignitrons 12V and 13V. When'the ignitrons fire, the transformer T3 is energized with alternating potential to energize the electrodes E for applying welding current to the workpiece W.

tion of cool time by the network 22. At the end of cool time, the next voltage peak of the curve Eg will cause the .thyratron 7V to re-conduct and establish a subsequent heat time and energization of the welding :electrodes ;as above described. Chi-1586s B5 and B6 are prevented from conducting and to i Each time :that the thyratron 7V conducts :to establish 8,874,& l at a heat time period, the resistor R11 will be energized to provide a blocking bias potential between the shield grid and cathode of the thyratron 2V to prevent this thyratron from firing even though the weld interval timing network 12 should time out during such a heat period. At the end of the weld time interval, the network 12 will have timed out to remove the blocking bias potential between the grid and cathode of the thyratron 2V. If this occurs during a heat time period the thyratron 2V will not conduct until the end of the heat time then in progress. If such time out occurs during a cool time thyratron 2V will immediately conduct. When thyratron 2V conducts thyratron 3V trails and these thyratrons complete a circuit between the busses B2 and B3 through the now closed contacts CR2c, the thyratrons 2V and 3V, the resistor-capacitor network 46, and transformer T4, applying full cycle potential to the transformer T4. When energized, the transformer T4 establishes a direct current bias potential across the resistor R7 which overrides the peaking conducting pips of the voltage wave Ega to prevent further firing of the thyratron 7V. Thyratron 7V being thus prevented from firing, thyratron 6V continues to conduct to maintain thyratrons 8V and 9V blocked.

Conduction of the thyratron 2V connects the cathode of the thyratron 4V to the bus B1 whereby hold time network is connected between the grid and cathode of thyratron 4V and further charging of this network 14 is prevented. Network 14 begins to time out and at the end of the hold time the thyratron 4V conducts to rapidly charge the off time network 16. When charged the network 16 places a blocking bias potential between the grid and cathode of the thyratron V to block the same for deenergizing the winding 26 of the relay CR1. When deenergized, the relay CR1 opens its contacts CRla, CRlb and CRlc, and closes its contacts CRld. Opening of the contacts CRla deenergizes the ram mechanism for moving the electrodes E away from the work W. Opening of the contacts CRlb opens the circuit in shunt with the switch SW1 which, if the switch SW1 is still closed as now assumed, is without effect. Opening of the contacts CRlc disconnects the cathode of thyratron 1V from the bus B2 and terminates further conduction of this thyratron. When thyratron 1V stops conducting, the energizing winding 28 of the relay CR2 is no longer energized and the contacts CR2a, CR2c and CRZd open and contacts CR2b close. Opening of the contacts CRZa is without efiect since in the conditions stated the single-repeat switch SW2 is in its open or repeat position. Opening of the contacts CR2c disconnects the cathode of the thyratron 2V and anode of thyratron 3V from the bus B2 therebyterminating further conduction of these thyratrons. Closing of the contacts CR2b connects the cathode of the thyratron 2V through a resistor R31 to the bus B3 thereby permitting the weld interval timing network 12 to charge by grid conduction in the thyratron 2V. Opening of the contacts CR2d opens the anode circuit of the thyratron 7V preventing this thyratron from again conducting. Termination of conduction of the thyratron 2V terminated the conduction of the thyratron 4V which terminated further flow of charging current to the off time network 16, which network then begins to time out.

At the end of ofi time the network 16 has snfiicient- 1y discharged to permit the thyratron 5V to re-conduct to initiate a subsequent cycle as above described, provided however, that the switch SW1 has remain closed. If, at the time the thyratron 5V was blocked to deenergize the relay CR1, the switch SW1 was open, the opening of the contacts CRlb would immediately open the anode-cathode circuits of all the thyratrons 1V, 2V, 3V, and 4V, permitting the networks 10, 12 and 14 to recharge and the network 16 to immediately start discharging, after which a re-closure of the switch SW1 would initiate a subsequent operation as described above.

If the switch SW2 is in its closed position for single operation irrespective of the time interval in which the switch SW1 is maintained closed, the initial conduction of the thyratron 1V results in closure of the contacts CRZa, as above described, whereby the contacts CR2a now complete a holding circuit between the anode of the thyratron 1V and the bus B2 through the emergency stop switch SW3 which is in shunt with the circuit through the thyratron 1V and the contacts CRlc. With this arrangement, once the relay CR2 becomes energized it will remain energized until the concurrent opening of the switch SW1 and contacts CRlb, thereby preventing the opening of the contacts CR2c to terminate conduction of the thyratrons 2V, 3V and 4V so that the off time network 16 continues to be charged and to maintain the thyratron 5V blocked. The relay CR1 cannot become deenergized until the switch SW1 is opened.

It will be appreciated that, if desired, the network 98a may be used in place of the network 98 and the potential established between the

terminals

150 and 152 which will have the same wave shape as that established between the

terminals

122 and 124, may be substituted therefor. In Fig. 3, however, this potential is applied across a rectifier 148 and combined with a potential established by a timing network 146 to control the thyratron 14V. In normal operation, alternating potential is applied between the busses B5a and B6a. The thyratron 14V will, however, not conduct due to the open condition of the normally open switch SW5. Since the cathode of the thyratron 4V is connected to the bus BSa through a resistor R32 and the grid of the thyratron 14V is connected through the network 146 and rectifier 148 to the bus 36a, the capacitor of the network 146 will be charged due to grid current flow through the thyratron 14V. When the switch SW5 is closed, the potential of the cathode of the thyratron 14V is transferred from substantially that of the bus B5a to that of the bus B6a and the potential across the network 146 is applied as a blocking bias potential between the grid and cathode of the thyratron 14V and further flow of charging current to the network 146 is terminated to permit it to discharge. The potential established by the network 98a is applied across the rectifier 148 which is in a polarity such that the rectifier easily passes all of the portion of the wave Eg below the zero axis leaving only the voltage pips Ega appearing thereacross due to the network 98a. These are superimposed on the normal discharge curve of the network 146 and when the network 146 has sufficiently discharged, one of these pips will bias the thyratron 14V into conduction at a given point in the half cycle of the voltage wave in which bus B5a is positive with respect to bus B6a whereby the thyratron14V conducts to energize the load 154 connected between the bus a and the anode of the thyratron 14V.

While there is shown and described herein certain preferred forms of the invention, it is to be distinctly understood that many modifications thereof may be made within the scope of the invention and the scope of the invention is to be determined by the scope of the hereinafter appended claims.

' What is claimed and is desired to be secured by United States Letters Patent is as follows:

1. In a device for supplying a series of peaked pulses, a phase-shifting network energized from a source of alternating potential and having an output circuit, a pair of output terminals, a resistor network connected in series between said terminals, a pair of unidirectional currentconducting devices connecting said circuit to said resistor network whereby the potential appearing across said resistor network appears as a series of rectified voltage pulses, and means connected in series with said resistor network for superimposing an alternating potential thereon at the same frequency as that of said source.

2. The combination of claim 1 in which the phase of zeta-s14.

said superimposing means is difierent from that in said output circuit.

3. In a device for supplying a series of peaked pulses, aphaseshifting network energized from a source of alter nating potential and having an alternating potential output phase'shifted from that of said source, a pair of outishi'fting network.

'5. The combination of claim 3 in which the output of said phase-shifting network is connected to the primary winding of a transformer having a secondary winding, means connecting a portion of said secondary winding tosaid resistor through said unidirectional device,

and said potential-producing device comprising a resistor connected to a portion of said, secondary Winding.

6. The combination of claim '5 in which a reactive device is connected in series with said last-named resistor.

7. 'The combination of claim 6 in which said reactive device .is a capacitor.

8. In a peaking system, a pair of terminals for connection to a source of alternating potential, a phase-shiftin'gapparatus having input connections connected to said terminals and an output connected to said terminals and an output circuit, a transformer having input connections connected to said output circuit and having a plurality of output terminals, a first and a second resistor connected together in series and having a common terminal and individual end terminals, means including a first unidirectional current fiow device connecting one of said end terminals to one of said output terminals, means including a secondunidirectional current flow device connecting said one end terminal to a second of said output terminals, said unidirectional devices being polarized to provide for current flow between said one end terminal and said transformer in the same direction, a circuit connecting said common terminal to a third terminal of said transformer, said third terminal being intermediate said first and second output terminals, and circuit means including a reactive component connecting the other of said .end terminals to said second output terminal.

9. A network of thecharacter described comprising a transformer, and having input connections for connection to a source of alternating potential, a first resistor, means connecting said resistor for energization by said transformer and including rectifying means whereby said resistor is pulsatingly energized, a second resistor, a reactive component, means connecting said second resistor and said component in series circuit across at least a portion of said transformer, and an output circuit connected to said resistors for producing a voltage in said output circuit which is a function of the sum of the volt age appearing across said resistors.

10. A network of the character described comprising a transformer having an output winding portion, a first network connected across said winding portion, said first network comprising a resistive component connected in series with a reactive component, a second network connected across said. one winding portion and comprising a resistive component connected in series with a reactive component, a pair of circuits connected between a point in .said first network intermediate its said. components to a point in said second network intermediate its said components, each said circuit including a unidirectional current flow device series connected with a voltage-producing component, the said device of one of said circuits being polarized to permit current ffiow through said component of said one circuit during aone half cycle of potential applied thereto, and the said device of the other of said circuits being polarized to permit current flow through said component of said other circuit during the other half cycle of potential applied thereto.

11. The combination of claim 10 in which said components of each of said circuits are connected to one of said networks and said unidirectional device of each said circuit is connected to the other of said networks.

12; The combination of claim 11 inwhich said transformer has a second winding portion, and a circuit connects said second winding portion and said voltage-producing components in series circuit.

13. The combination of'claim 11 in which analternating potential-producing device is provided and a circuit connects said last-named device and said voltage-producing components in series.

14. Apparatus for producing a pulsating potential of peaked form which is of one polarity once each cycle of the alternating supply voltage comprising a first pair of terminals adapted to be supplied with a first source of alternating potential, a second pair of terminalsadapted to be supplied with alternating potential which is of different phase from that of the potential supplied to said first pair of terminals, a first voltage-producing component, a rectifier, means connecting said component and :said rectifier across said second pair .of terminals, a second voltage-producing component, means connecting said second component across said first pair of ter- .minals, and circuit means connecting said components to. an output circuit.

No references cited.