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Патент USA US2404971

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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.
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