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Dec. 17, 1946.
rim nec. 1v. 194s
Patented Dec. 17, 1946
David Packard, Palo Alt 0, and Noel
EI Porter,
Berkeley, Calif., assignors to Hewlett-Packard
Company, Palo Alto, Calif., a copartnership
consisting of William R. Hewlett and David
Application December 17, 194s, serial No. 514,648
4 Claims.
This invention relates generally to electric arc
welding systems of the motor generator type, and
particularly to welding systems adapted for au
tomatic control.
In welding systems of the above type it is con
ventional practice to make use of a starter switch
in the alternating current supply lines to' the
motor, and with this switch having control cir
cuits conditioned by start and stop contacts for
causing automatic closing of the starter switch
with resultant starting of the motor generator in
operation responsive to snorting the welding rod
upon the work preparatory to striking an arc.
Systems of» this type which have been developed
in the past have been unduly complicated, and
have generally required direct interruption of the
welding circuit by means of heavy duty switch
contacts. Furthermore prior systems have not
been readily adaptable to various prevailing com
mercial types of motor generator welding equip
It is an object of the present invention to pro
vide a simple and effective system of the above
(ci. 1v1-_97)
tion, but in general it consists of contact sets I,
2, 3 and 4 which are moved to closed position
upon energizing the operating coil Il. Manually
operated start and stop contacts I'I and Il serve
to initiate closing and opening of the main
switch contacts through the action of coil I3. In
addition it is customary to provide overload re
lease contacts I9 in series with contacts I3.
In the present instance the control circuits ci'
10 the starter switch are electrically related to the
welding circuit through means including the
transformer C, and the magnetic relay or switch
D. In addition supplemental relays E, F and G
are provided for functions which will be presently
15 explained.
The relay D is constructed with an operating
coil 2| of relatively low resistance and reactive
impedance, whereby it can be connected perma
nently in series with the welding circuit I2. In
practice a magnetic core
22 has been employed,
with the heavy Welding conductor I2 simply
looped through one leg of this core, as illustrated
One side of the coil for relay G is s_hown con
25 nected to contact 3 of relay» A, and the other side
of this coil connects to conductor 23, which ex
tends to the line LI. Contact 2 of relay G is
connected by conductor 24 to one of the set of
character, which is characterized by an absence
of contacts for interrupting the welding circuit. 30 contacts 4 of the starter switch B. Contact 5
Another object of the invention is to provide a
of relay G is connected by conductor 25 to the
system of the above character which can be read
other side of the contact set 4.
ily applied to prevailing types of welding equip
Transformer C has its primary terminals con
nected to conductors 23 and 24 by conductors 2l
and 28. One side of the secondary of this trans
former is grounded, and the other side connects
through conductor 29 with the welding circuit
conductor I2. Contacts I and 2 of relay E are
A further object of the invention is to provide
a novel arrangement for indicating or‘registering
the total arc time of the system over an extended
time period of operation.
Further objects and features of the invention
connected in series with conductor 29. Also a
series protective fuse 30 can be provided.
will appear >from the following description in
which the preferred embodiment has been set 40 The operating coil of relay E has its one side
forth in detail in conjunction with the accom
connected to conductor 28, and- its other side to
panying drawing.
v .
the contact 2 of relay F. Contact I of relay F
is in' turn connected to conductor 24.’ Contact
3 of relay F is connected by conductor 32 to con
drives the direct current welding generator II. 45 tact I of relay D. The operating coil
Alternating current supply lines LI, L2 yand L3
F has its one side grounded and its other side
The system as illustrated in the drawing con
sists of an alternating current motor I II which
supply current to the motor I0 through the line
connected «by conductor 33 to the we1ding`con
switch A and starter switch B. One side of the
generator I I is shown grounded and the other
ductor I2.
side is connected to the welding conductor I2,
switch and is in series with the stop contact I8,
is connected to contact 2 of relay G. Contact I
of this relay is connected to conductor 25.
which extends to the welding wire or rod I3. The -
Conductor 34, which leads from the starter
work or object III being welded is likewise shown
In addition to the equipment referred to above
as grounded to complete the welding circuit.
The starting switch B may vary in construc 55 the system preferably includes a tctalizing de
vice 36 connected by conductors 3l and 33 to
y, anarco
3 and _to open its contacts I and 2. Opening of
conductor 28 and to contact l of relay D. This »
totalizer can be any suitable counting or time in
contacts I and 2 insures deenergization of relay
E irrespective of momentary deenergization of
» dlcating device, consisting for example of a con
relay D.
stant speed synchronous motor driving suitable
counting means.
When the motor generator reaches normal
speed the operator draws an arc between the work
Relay G is a time delay device constructed so
and the welding rod I3, and proceeds with nor
that upon energizing its operating coil the con
mal Welding operations. The welding current
tacts I and 2 are opened after a predetermined
maintains the relay D energized, with contacts
time period of continuous excitation. Should 10 I and 4 closed to supply alternating current to
current through the coil of this device be in-`
the totalizer 36, but the winding of delay relay
` terrupted momentarily, the device is automati
G is deenergized by virtue of contacts I and 3
cally reset, whereby thereafter continuous ex
being open. The welding equipment remains in
citation for the entire period of delay is required.
this condition as long as normal welding pro
Time delay relays of this typexare well known in
ceeds. Should Welding operations be interrupted
the art, and can consist for example of a small 15 relay D is deenergized with the result that con»
self-starting synchronous motor, geared to open
tacts I and ii are closed, and contacts I and f3,
the contact after a predetermined period of con
together with contacts 2 and E, are opened. This
tinuous operation, and with provision for auto
results in energizing the delay relay G, but does
matically interrupting the gear train to permit
not immediately alter the closed condition of
immediate resetting when excitation is inter 20 the starting switch B. Should welding be re
sumed before a sumcient time has lapsed ior
The relay F, which can be termed a protective
relay G to open its contacts I and 2, then relay D
is again energized, and the winding of delay relay
relay, is adapted for direct current operation at
a potential below that normally maintained across
G deenergized whereby the motive element of the
the welding arc. For example with a welding 25 same is restored to its initial position. If the
generator adapted to maintain about 25 volts
welding current is interrupted for a period of
across the arc during normal welding operations,
time equal to that to which the delay relay G is
the relay can be wound to operate at a potential
adjusted, then the contacts I and 2 oi’ the delay
relay are opened, with the result that flow of
of about 10 volts.
Operation of the system described above can 30 current through coil Ie is interrupted, and the
starting switch B is immediately opened to dis
be outlined as follows: With the line switch A
openthe system is completely deenergized. Upon
continue supply of current to the motor III. Be
closing the line switch A. transformer C is ener
gized, relay E is energized to maintain its con
, fore the motor generator comes to rest the voltu
age applied to the winding of relay F drops suf
35 ficiently to cause opening oí contacts I and 3
tacts I and 2 closed, and potential from the sec
ondary of transformer C is applied to the welding
and closing of contacts I and 2. The system is
conductor I2. The circuit for energizing the
now ready for restarting in the manner previously
described, that is by shorting the rod I3 upon
transformer C can be traced from line LI, con
ductor 23, conductors 2l and 28, conductor 25,
work IQ.
contacts I and 2 of delay relay G, conductor 36 40
It Will be noted from the above that the total
and contacts I8 and I9 which connect vto line L3.
izer 3S is connected and is in operation only dur~=
The coil of relay E is energized in that its one
ing periods of arc welding, when normal weld
ing current is flowing through the welding cir
side connects with conductor 28, and its other
closed contacts I and 2"-~
cuit. Therefore over a considerable period of
of relay F, conductor 2li, and coil I6, which in 45 time the readings of this device will be cumu
turn connects to conductor 21. The impedance
lative and will shc'f': the total period of arc weld
of the coil for relay E is such that the current
ing time for which the machine was in use. It
iiow through coil I6 is insumcient to operate the
is necessary that there be a substantial voltage
starter switch. Relay D remains deenergized,
across the arc, as well as a ñow of welding cur
and totalizer 36 is not energized because contacts 50 rent, for the totalizer to operate. This is be
I and II are open.
' To start the motor generator in operation the
operator short circuits the welding rod I3 upon
the work II. This causes a momentary surge of
current from transformer C through the coi1 2I 55
of relay D, thereby causing the closing of con
tacts I and 4, and also contacts 2 and 5. Closing
of contacts 2 and 5 of relay D effectively short
circuits the starting contacts I'I. This causes
the coil I6 of the starting switch to be energized 60
with sufficient current to cause the contact sets,
I, 2, 3 and 4, to be closed. Closing of contacts
4 short circuits or locks out the starting contacts
I1, and also the contacts 2 and 5 of relay D.'` Thus' '
while the motor is being started in operation, the 65
transformer. C need not continue to supply suñ'i
cient current to coil 2| to maintain relay D en
ergized. Simultaneously with relay D being en
ergized the coil of relay E is deenergized to open
cause relay F must be energized as well as relay
D, for current to be supplied to the totalizer.
Relay F is deenergized if the welding rod is short
ed to the"work, because at that time the voltage
across the arc is reduced to zero or to a value
so low that relay F is not energized. Thus the
totalizer does not count or record time when the
arc is not in actual working operation.
The complication of. a breaker switch inl the
Welding circuit itself is completely eliminated with
the present system, and relay D may be of rela
tively light construction, with its contacts de
signed tc handle the relatively small current:
required. Relay F in conjunction with relay l
insures an open secondary circuit for the trans
former C during normal welding operations, thu
protecting the transformer against unduly heav:
loads by virtue of the low impedance of the weld
ing circuit to ground.
its contacts I and 2 and thus interrupt the sec 70
It will be evident that our invention is appli
ondary circuit of transformer C. This occurs
cable to various makes of motor generator equip
because the coil of relay E is shorted out by the
. ment having various types of starting switcha
closing of contacts 2 and 5 of relay D. .As the
Such circuit changes as are required for differ
direct current potential from generator I I builds
ent typesof starting switches will be apparenti
up, relay F is energized to close its contacts I and 75
those skilled in the art, and will not alter the
principle of operations.
We claim:
1. In a welding system of the type having a
motor connected to alternating current supply
provision for automatically closing and opening
the same in response to the closing and opening
of control circuits, a relay having a low imped
ance energizing coil in series with the welding
2. In a. welding system of the type having a
nected to receive direct current from the weld
ing circuit and adapted to interrupt the energiz
ing circuit of the last named relay.
3. In a. welding system of the type having a
motor connected to alternating current supply
lines through a starter switch and a direct cur- 70
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