Sept. 26, 1944.
H. PURAT
2,358,826
WELDING MECHANISM
Filed May 19, 1941
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Sept. 26, 1944.
|-|_ PURAT
2,358,826
WELDING MECHANISM
Filed May 19, 1941
2 Sheets-Sheet 2
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INVENTOR
BY
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R N E Yti
2,358,826
' Patented Sept. 26,
UNITED STATES PATENT OFFICE
2,358,826
WELDING MECHANISM
Hugo Purat, Detroit, Mich, assignor to Progres
sive Welder Company, Detroit, Mich; a
ration of Michigan
Application May 19, 1941, Serial‘ No. 394,118
4 Claims. (Cl. 219-4)
The present invention relates to welding mech
a mechanism embodying control means for caus
anisms, and in particular is directed to the pro
vision of an improved mechanism for controlling
relative movements of and the operating pres
ing the flow of welding current to occur during
the ?nal movement of the actuating mechanism
so as to facilitate the take-up movement of the
sures between the electrodes of a spot welding
welder which occurs as a consequence of the sof
machine.
tening of the metal.
7'
_
,
The principal objects of the present invention
With the above, as well as other Objects in
are to provide a mechanism of the above gen
view, which appear in the following description
erally indicated type, which is simple in con
and in the appended claims, a preferred but illus
struction, economical of manufacture and assem 10 trative embodiment of the invention is shown on
the accompanying drawings, throughout the sev
bly, and which is reliable and e?lcient in opera
tion; to provide such a mechanism characterized
eral views of which corresponding reference
as embodying means for limiting the pressure be
characters are used to designate corresponding
tween the electrodes to a predetermined but ad
parts and in which:
,
Figure 1 is a perspective view of a welding ma
justable value; to provide such a mechanism in
which the welding pressure is transmitted to a
chine embodying the invention;
Fig. 2 is an enlarged view, psrtiy in section,
movable electrode, from an associated source of
power, through an intermediate chamber which," showing the invention;
is adapted to be charged with a compressible ?uid
Fig. 3 is a view in section, taken along the line
and which limits the pressure applied to the mov- 20 3-—-3 of Fig. 2;
_
'
Fig. 4 is a view in section, taken along the line
able electrode; to provide such a mechanism
4-4 of Fig. 3; and
wherein the just-mentioned ?uid chamber is em
Fig. 5 is a fragmentary sectional view, taken
bodied within a primary ram, which may be se
lectively actuated between a retracted loading ‘ along the line 5-5 of Fig. 3.
position and an intermediate position and a 25
It will be appreciated from a complete under
welding position in which the movable electrode
standing of the present improvements that in a
engages the work with the predetermined .pres
generic sense they may be embodied in machines
sure; to provide such a mechanism wherein the
intended for widely varying types of service. A
primary ram comprises a cylinder and a primary
preferred use of the inventtion is in connection
piston movable therein, the primary piston being
30 with the control of the movements of the mov
organized to accommodate a secondary piston,
able electrode of a spot welding machine and the
control of the pressure transmitted through the
work by the movable and stationary electrodes of
of the primary piston to advance the movable
such machines. Accordingly, in an illustrative
electrode from the intermediate position to the
welding position; to provide such a mechanism 35 but not in a limiting sense, the invention is so
wherein the aforesaid pressure limiting means is
illustrated herein.
g -.
interposed between the secondary piston and the
Referring to the drawings, the illustrative ma
chine comprises a main generally box-like frame
movable electrode; to provide such a mechanism
I0, having upper and lower horns l2 and it pro
wherein the pressure limiting means is consti
tuted by a chamber formed between the sec 40 jecting in vertically spaced relation from the
front wall thereof. The upper horn l2 a?ords a
ondary piston and a third piston, which chamber
support for the hereinafter described‘ supporting
is adapted to be charged with a compressible
and actuating mechanism, associated with the
?uid; to provide such a mechansim embodying
improved means for forming a clamping connec
movable electrode l8, and the lower horn 14 con
which secondary piston functions after operation
tion between a supply conductor and the mov
able electrode; and to generally improve welding
‘ mechanisms of the above generally indicated
45 stitutes a support for the lower or stationary
electrode 20. To the extent thus far described,
the welding machine is conventional and it will
type.
be understood that the work illustrated as com
prising a pair of metallic sections W may be in
Further objects of the present invention are to
provide a mechanism of the above generally in 50 terposed between the electrodes l8 and 20, after
which the same are brought into engagement
dicated type, wherein a fluid or elastic coupling
with each other with a predetermined pressure.
of the above indicated type between a welder and
its actuating mechanism enables the actuating
To complete the welding operation, current is
caused to pass through the work and the elec
trode has engaged the work; and to provide such 55 trodes I8 and 20 for a predetermined welding
mechanism to continue to move after the elec
'
2,
..
2,358,826
.
an opening provided therefor in the lower end
44 of the primary cylinder 48. The lower end of
the piston rod 88 is rigidly but separably con
nected to the previously mentioned column 30 by
period, after which the pressure is relieved from
the electrodes l8 and 20, allowing the work to be
removed therefrom.
In accordance with the present invention, the
movable electrode i8 is removably secured to the
means of a drive pin 94.
The chamber 96, which is formed within the
cal guiding support from and is vertically slid
secondary piston ‘l4, constitutes a pressure lim
able within a cylindrical guiding portion of a
iting means or ?uid lock, as hereinafter described,
to determine the maximum pressure which may
bracket 84. The rear face of the bracket 34 is
provided with a transversely and vertically ex 10 be transmitted to the work through the electrode
tending supporting plate or ?ange 38, which is
86, and this chamber is continuously connected
adapted to seat against a corresponding portion
to a suitable sourceof ?uid, such as air, at a uni
38 provided at the forward end of the upper
form pressure, through a tubular connection 98,
which projects downwardly through, but in free
horn i2._ The bracket 34 is adapted to be se
lower end of a column 3!! which receives verti=
cured in place on the horn H by means of a 15 ly spaced relation to the walls of, the sleeve 84.
The lower end of the connection 96 is threadably
secured to the piston member 78 and opens di
The upper end of the bracket 34 is provided
rectly into the chamber 86.
with an annular ?ange 42, which forms a seat for
plurality of studs 40.
The actuating ?uid for causing the second
the lower end 44 of the .primary cylinder 46. The
upper end of the cylinder 46 is closed by means 20 ary piston 14 to move downwardly is admitted to
the portion 14a of cylinder 52, which is above the
of a removable cover plate 48. A series of studs
piston l4, through a plurality of angularly ex
such as 50 may be utilized to secure the cover
tending ports I 00, which open into the just-men
plate 48 in place and a corresponding series of,
studs 53 may be utilized to secure the cylinder 46
tioned chamber space, and also open into the an
to the bracket 34.
25 nular space I02 between the sleeve 84 and the
The cylinder 48 slidably receives a primary pis
connection 98. The upper end of the just-men
tioned annular space 502 is connected through a
ton 52, which in itself constitutes a secondary cyl
inder and is composed of a head 34 and an up
valve N14 to a line Hi6, which may extend to the
wardly presenting cuplike body 58. The mem
same source of supply as is provided for the
bers 54 and 58 are threadably secured to each 30 chamber 96.
.
other, as indicated at 58, and conventional seal—
Fluid is admitted to the primary cylinder 48
ing gaskets such as 60 and 82 may be utilized
for the purpose of causing the primary piston 52
to prevent leakage of the actuating ?uid around
to move downwardly through a port I08, which
the primary piston 52. The member 54 is pro
opens \into an annular groove H0 formed in the
vided with an integral upwardly extending sleeve 85 underside of the cylinder head 48. The port id!
64, which slidably passes through the cylinder
‘is adapted to be controlled by a usual four-way
head 48 and carries a motion limiting member
valve H2 (Fig. 1).
v
illustrated as being a rotatable hand wheel 68,
Preferably and as illustrated, the primary pis
having a lock nut 68 associated therewith. As
ton 52 is returned to its retracted position by
will be understood, by releasing the lock nut 40 admitting air to the chamber space below pis
68, the hand wheel 68 may be turned so as to
cause it to travel upwardly or downwardly rel
ative to the sleeve 84. In operation, as here
ton 52 and for this purpose a passage H6 opens
into the lower end of the cylinder 48 and is pro
vided with a connection H8, which is also con
inafter described, the under surface ‘in of the
trolled by the valve H2.
hand wheel seats against the upper surface '82 45
It will be appreciated that, if desired, suitable
of the cylinder head 48 to limit the downward
reducing valves or other mechanism (not shown)
movement of the primary piston 82 and thus
may be interposed between the source of supply
determine the location of the hereinafter de
and the previously mentioned supply conduits 98, v.
scribed intermediate position of the movable elec
H08, H18, and H8, so as to afford desired relations
trode l8. In the retracted position of the mov 50 between pressures exerted through these connec-'
able electrode it, the upper end of the primary
tions, and it will further be understood that flex
piston 52 engages the underside of the cylinder
ible means (not shown) may be interposed be
head 48, which engagement thus determines the
tween the conduit 98 and the source of supply
location of the retracted or loading position or
so as to accommodate the hereinafter described
the machine.
'
55 reciprocating motion of the conduit 98.
The primary piston 62 slidably receives a sec
ondary piston 14, which is constituted by a head
76 and an upwardly presenting cuplike member
18. The members 18 and 78 are threadably se
cured to each other, as indicated at 80, and are 60
-
It will further be understood that the valve
804 may be of the usual electromagneticaily op
erated type. which in its de-energized position,
closes 011 the connection between the passage
its and the supply line we and connects such
continuously urged to the illustrated position
passage i 02 to exhaust and which, in its energized
in which the head ‘It bears against the underside
position, closes ed the just-mentioned exhaust
of the head I54 by means of a compression spring
connection and connects passage I02 to the sup
82. The spring 82 is seated between the under
ply line M6. Valve H2 is illustrated in Fig. l as
side of the member ‘i8 and the upper surface of 85 being a conventional manually operable four-way
the primary piston member 58.
valve, having pedals‘ i i241 and “2b. In the illus
The secondary piston '14 constitutes a cylinder
trated position in which pedal “2b is depressed,
which slidably receives a tertiary piston 84', which
port M8 is connected to the associated exhaust
is provided with an integral downwardly pro
line H5 and port H6 is connected to the supply
jecting piston rod 88. The piston rod ii! is guid 70 line H4. It will be understood that if pedal H24
ingly supported by the cooperating bearing por
is depressed, the just-mentioned connections are
reversed, port H8 being connected to the exhaust
tions 88 and 90, which are formed within the
line H5 and port Hi8 being connected to the sup’
tubular piston rod 92. The piston rod 92 is in
tegral with and projects downwardly from the
secondary piston '14 and slidably passes through 75
ply line H4.
I
-
In accordance with the present invention, a
2,858,826
clamping member I20 embraces the column 30,
which carries the movable electrode I8, and may
be selectively controlled to release the sleeve 32
or to clamp the same.
The'usual ?exible leads
I22, which connect the movable electrode to the
3
pieces may be introduced into the space between
the electrodes I8 and 20 while the latter are in
relatively widely spaced relation to each other.
As soon as the workpieces are properly located,
as just-mentioned, pedal II2a of valve II2 may
corresponding terminal of the supply circuit, are
connected to the clamp I20 and to the relatively
stationary bus bar I24 which projects forwardly
be operated to admit operating ?uid to the pas
sage I08, which thereupon builds up a pressure
within cylinder 48, and to connect line II8 to
exhaust. The building up of the just-mentioned
into the upper horn I2 of the machine. This
clamping mechanism embodies certain improve 10 pressure causes the primary piston assembly to
ments upon the corresponding arrangement de
move downwardly, as viewed in Figs. 1 and 2,
scribed and claimed in my Patent No. 2,304,121
until such a time as the underside of the hand
of December 8, 1942, and assigned to the assignee
wheel 68 engages the seat ‘I2 provided therefor on
the cylinder head 48. The just-mentioned limit
hereof.~ As shown, the clamping member I20 is
of generally U-shaped form, having radially ex 15 is, as previously mentioned, adjustable and is
tending legs I26, the outer faces whereof are pro
preferably set to interrupt the movement of the
vided with tapered faces for wedging engage
primary piston 52 at a time when the movable
ment with rollers I28, which are carried by a yoke
electrode I8 is of the order of three-eighths of
I30. The yoke I30 is connected to a piston rod
an inch from the work.
I32 associated with a piston I34, which is re 20
To initiate a welding operation, the valves I84
ciprocable within a cylinder I38. The cylinder
and I58 may be operated in sequence, and for this
I36 is provided with forwardly extending legs
purpose the switch S (Fig. 1) may be depressed.
I38, the outer ends whereof are seated upon
The control mechanism for causing the opera
shoulders I40 provided at the respectively op
tion of valves I04 and I58, in response to the
posite sides of the clamp I20. Studs I42 are 25 operation of switch S and for also causing the
threaded through the arms I38 and into the body
of the clamp I20, and serve to rigidly secure the
.?ow of welding current in response to the same
operation, may be variously arranged. A pre
ferred arrangement is shown in my patent above
yieldingly supported from the adjacent portion
mentioned. In utilizing the just-mentioned con
34a of the previously mentioned bracket 34, by 30 trol system, the switch designated P in the pat
means of a pair of oppositely disposed compres
ent corresponds to the switch S mentioned above,
sion springs I44, which are received in bores in
and the valves designated 84 and I06 in the pat
cylinder I38 to the clamp. The clamp I20 is
dividual
thereto.
Adjusting
screws
I48
are
ent correspond, respectively, to the valves I04
threaded into the lower end of the just-men
and I58 of the present application.
tioned bores and serve to adjust the tension of 35
The‘ operation of valve I04 admits ?uid pres
the springs I44. As clearly appears in Figs. 2, 3
sure through the passage I02 and the pas
and 4, two of the previously mentioned ?exible
connectors I22 are employed, and are arranged
at respectively opposite sides of the clamping as
sembly. The outer end of each ?exible con
nector is secured to the clamp I20 by means of
an associated stud I48 and the other end of
each ?exible connector is secured to the pre
viously mentioned bus bar I24 by means of an
associated stud I50.
sages I00 into the previously identified cham
ber space 14a above the secondary piston ‘I4, and
as the pressure builds up in this chamber, sec
ondary piston 14 is caused to move downwardly
in opposition to the force of the compression
spring 82. Under the conditions stated, a ?uid
pressure, proportional to the pressure supplied
through the line 98, exists within the ?uid lock
' chamber 98 and this pressure causes the tertiary
It will be appreciated that the clamp I 20 is
piston 84 to move downwardly simultaneously
formed of spring-like material and tends to as
with the secondary ‘piston ‘I4 until such time as
sume an expanded position in which the sleeve
the movable electrode I8 engages the work.
30, which carries the electrode I8, can freely
As soon as the movable electrode I8 engages
move upwardly and downwardly relative to the 50
the
work, further downward movement thereof
clamp I20. The tendency of the clamp I20 to
is interrupted and thereupon, as described in
expand may be relied upon to urgev the piston
the patent, the valve I58 is operated to admit
I34 to its righthand position, but preferably and
?uid pressure to the cylinder I36 and actuate the
as illustrated, a compresison spring I54 is pro
clamp
I20 into clamping engagement with the
vided for this purpose. Air or other suitable
elastic ?uid is admitted to the cylinder I34 55 sleeve 30, associated with electrode I8. The lat
ter action electrically connects the electrode I8
through a connector I56. The connector I58
to
the bus bar I24, and as soon as this is accom
may be connected to the previously mentioned
plished, the welding circuit may be completed
source of ?uid pressure, through a valve I88, by
to initiate the ?ow of welding current.
means of a connector I60. It will be appreciated
As will be appreciated, the downward move
that the valve I58 may be of the type previously 60
ment of the secondary piston ‘I4 may continue
described in connection with valve I04.
after the movement of the tertiary piston 84 is
Considering now the operation of the system
interrupted, a lower limit to such downward
as a whole, it will be appreciated that the parts
movement being reached when the underside of
are shown in the various figures in the retracted
positions thereof, under which conditions, as 65 piston ‘I4 engages a cooperating annular shoul
der 82a provided therefor adjacent the base of
previously mentioned, the primary piston 52 is
the primary piston 52. This limit is reached be
maintained in its elevated position by the fluid
fore the underside of the head ‘I6 of piston ‘I4
pressure admitted through the line II8, the pis
engages the upper surface of the tertiary piston
ten 14 is maintained in its elevated position by
the spring 82, and the piston 84 is maintained in 70 84, so that under all conditions of operation, the
maximum pressure transmitted to the electrode
its illustrated position by the fluid pressure con
I8 is determined by the pressure supplied through
tinuously admitted to the chamber 96 through
the line 88. Preferably, the parts are propor
the line 88. It may be assumed that the work
tioned to allow for approximately ?ve-eighths of
pieces to be welded require the making of a plu
rality of separate spot welds, and such work 75 an inch of movement of the secondary piston ‘I4
4
V
-
.
.
.
.
asaaese.
after the movement of the tertiarypiston 84 is
interrupted.
Consequently, as soon as the metal starts to
soften, the already moving secondary piston ‘I4,
tioned take-up movement of the electrode it
without altering the pressure between the elec
together with the ?uid pressure existing in the
chamber 88, is enabled to immediately begin the
take-up movement of the tertiary piston 84 and
the movable electrode i8.
As previously mentioned, it iscustomary and
the aforesaid patent system is arranged to main
trodes.
tain the pressure between the movable and ?xed
As will be understood, the ?ow of welding cur
rent through the work softens the same and
allows some take-up of the metal. The pressure
within the chamber 88 produces the lust-men
This take-up‘ movement causes a corre
sponding slight downward movement of the 10 electrodes for a certain period after the ?ow of
current is interrupted, and it is to be expected
clamp I20, which slight downward movement is
that the secondary piston ‘II will reach its lower
permitted by the ?exible character of the con
limit of travel sometime during the Just-men
nectors I22, as will be understood. This down
tioned period. In all cases, however, the adjust
ward movement of the clamp I20 also loads the
supporting springs I“, associated therewith, and
renders them effective to restore the clamp ii.
15 ment is such that the secondary piston 14 be pro
vided with a su?lciently long stroke so as to main
tain this piston in motion throughout the period
in which the take-up movement of the movable
electrode occurs. Throughout the entire take-up
20 movement of the movable electrode, therefore,’
the secondary piston is effective to cooperate with
as described in the patent, after which the valves
the elastic pressure in the chamber 96, to cause
I58 and 104 are sequentially de-energized to ?rst
the take-up movement of the movable electrode
release the clamp I20 and to thereafter exhaust
58 to promptly follow the softening of the metal.
actuating ?uid from the chamber 14a, associated
Although only a single speci?c embodiment of
with the secondary piston ‘ll. As soon as the lat
the invention has been described in detail, it will
ter action occurs, piston 14 is restored to the
be appreciated that various modi?cations in the
upper position under the in?uence of spring 82
form, number and arrangement of parts may be
and carries with it the tertiary piston 54, thereby
made without departing from the spirit and scope
elevating the electrode I! to the previously iden
of the invention.
.
30
ti?ed intermediate position. This intermediate
What is claimed is:
position is high enough to allow the work to be
l. In a machine having a work engaging part,
moved to the next welding position, at which time
a piston connected to said part, a first cylinder
the previously described sequence may be com
within which said piston is received, means for
pleted. As soon as all welding operations on the
moving said cylinder, means for introducing an
workpiece in question are accomplished, the pedal
elastic ?uid at controllable pressure into said cyl
“2b of valve H2 may be depressed, thereby ex
to its normal position as soon as the welding op
eration is completed.
At the conclusion of the welding operation,
the ?ow of current is automatically interrupted,
hausing that portion of cylinder “'which is”. inder so as to urge said piston to move said part
to work engaging position as said cylinder is
above piston 52, and admitting ?uid pressure
moved, said elastic ?uid enabling said cylinder to
through line He, which actions restore the pri-‘
40 continue to advance after said part has reached
mary. piston to the position shown inll‘ig. 2.
said work engaging position, said moving means
As previously mentioned, the ?ow of welding
including a second cylinder for slidably receiving
current through the work softens the same and
said ?rst cylinder, and means for applying a ?uid
allows some take-up of the metal. It is impor
pressure between' said ?rst and second cylinders
tant that the pressure between the movable and,
so as to cause said movement of said ?rst cylin
stationary electrodes be accurately controlled
der.
throughout the period during which the welding
2. In a machine having a movable part, a pri
current is ?owing, and it is, therefore, essential
mary cylinder, 9. primary piston slidably received
to initiate a take-up movement of the movable
in said primary cylinder and formed to de?ne a
electrode as soon as the metal starts to soften
cylinder space, a secondary piston received in said
50
and that such take-up movement continue
last-mentioned cylinder space and formed to de
throughout the softening period. In welding cer
line a cylinder space, a tertiary piston slidably 4
tain classes of metal, such as aluminum, alumi
received in said last-mentioned cylinder space,_
num alloys, stainless steels, and the like, satisfac
means for continuously introducing an elastic
tory welding operations depend upon the use of
exceedingly high welding current values and ex~= 55 ?uid into sa‘d last-mentioned cylinder space so
as to act against said tertiary piston,_se1ectively
tremely short periods of current ?ow. For ex
controllable
means for introducing ?uid pressure
ample, the system of the aforesaid patent is ar
into said ?rst-mentioned cylinder and into the
ranged to limit the ?ow of current to one half
cylinder space provided in said ?rst-mentioned
cycle of the source, which, with a sixty cycle
system, is equivalent to 1/520 of a second. At the 60 piston, and means directly connecting said part
to said tertiary piston.
beginning of this fraction of a second, the mov
3. In a machine having a movable part, a pri
able electrode stationarily engages the surface of
mary cylinder member, a primary piston slidably
the work, and during the course thereof must be
received in said primary cylinder member and
started on its take-up movement. In the pres
ent arrangement, as aforesaid, the secondary pis 65 formed to de?ne a cylinder space, a secondary
piston member received in said last-mentioned
' ton ‘I4 is enabled to continue its downward move
cylinder space, means for continuously introduc
ment after the movable electrode 18 has engaged
ing an elastic ?uid into said last-mentioned cylin
the work, and in accordance with the present in
der space so as to ‘act against said secondary pis
vention, the parts are preferably so adjusted that
the secondary piston 14 remains in motion 70 ton member, selectively controllable means for
introducing ?uid pressure into said ?rst-men
throughout the period during which the welding
tioned cylinder space, means connecting one of
current is ?owing. With this relation, the fric
said members to said movable part, and means
tional engagement between the tertiary piston 84
for supporting the other of said members.
and the secondary piston 14 tends to cause the
tertiary piston 04 to advance toward the work. 75 4. In a machine having a movable part, a pri
2,858,828
mary cylinder member, a primary. piston slidably
received in said primary cylinder member and
formed to define a cylinder space, a secondary
piston member received in said last-mentioned
cylinder space, means for continuously introduc
ing an elastic ?uid into said last-mentioned cylin
der space so as to act against said secondary pis
ton member, selectively controllable means for
introducing ?uid pressure into said ?rst-men
tioned cylinder space, means connecting one of 10
5
said members to said movable part, and means
for supporting the other of said members, said
last-mentioned means including a cylinder mem
ber within which said primary cylinder member
is slidably received, and selectively controllable
means for introducing ?uid pressure into said
last-mentioned cylinder to act against said pri
mary cylinder member.
HUGO PURAT.