Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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IMPROVED ELECTRODES FOR USE IN THE EXTRUSION-
FUSION WELDING OF LEAD PARTS THROUGH AN APERTURE
IN A sATTERY CASE
sackground of the Invention
The present invention relates generally to apparatuses
for making intercell welds in electric storage batteries and in
particular to those apparatuses where electrodes are oriented on `
either side of a partition or other aperture in a battery case,
lugs or other battery parts are placed at each side of that aper-
ture, contact produced therebetween, current passed through the :
lead parts to melt the same, and pressure applied generally for
the purpose of providing an electrical connection through the
10 aperture. Such an apparatus is disclosed in U.S. Patent 4,013,864.
It has long been known that lead parts on either side
of a partition with an aperture formed therein can be welded
through that aperture using any one of a number of techniques.
In the lead acid battery art, the most common site for welding ~ ;~
through an aperture is during the formation of intercell connec-
tions, that is, in making the electrical connections between one
battery cell and the next and/or between the endmost battery cells
and the
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exterior battery terminal of the battery. Since
connections through apertures of this sort, in
addition to being electrical, must provide a liquid
seal from cell to cell to prevent "pumping", some
5 attention has been directed in the art concerning
various methods for insuring that an intercell con-
nector, in addition to providing a ~ood electrical
connection, will also exhibit good sealing charact-
eristics.
U. S. Patent No. 3,687,734 generally
discloses a connector for electricall~ connecting
two elements of a storage ba~tery through an aperture
wherein at least one of the connector lugs is pro-
vided with a passage extending therethrough. Molten
15 material from an internal portion of the connector
exits through this passage during the heat fusion
step as a result of pressure from a heat energy
build-up. ~he patentee attempts by this structure
to avoid the problem of blow-outs or lead expulsion
20 which has been encountered by many practitioners in
this art.
Another attempt to avoid "blow-out" is
disclosed in U. S. Patent No. 3,476,611 wherein inter-
cell connections are made by a projection welding
25 process from pins which extend through the partition
between two adjacent battery compartments, which
pins have dimensions such that, when they are
fluidized during the process, the volume o~ the pin
material does not exceed the volume defined by -the
30 walls of the opening.
Such attempts inherently involve tolerence
and positioning problems during manufacture and
assembly of the parts and battery. ~lore recently,
; other methods have been developed for producing
35 battery intercell electrical connections, which
methods have ~enerally been referred to as "extrusion-
fusion" type methods. For example, in U. S. Patent
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No. 3,79 ,086 a method is disclosed wherein flat
surfaced connector lugs are nlaced on each side of
the battery partition wall, adjacent an aperture.
The connector lugs are extruded by a pair of opposed
S electrodes into the aperture until they meet, where-
upon an electrical welding current is applied. When
the weldin~ current ceases, the connector is allowed
to cool. U. S. Patent No. 3,793,086 states:
"It should be emphasi~ed that reduction
of the initially applied shear force
during the welding cycle is essential.i
If the high applied shear force is main-
tained during the welding cycle, molten
lead will be squirted from the welding
joint and an imperfect joint can result."
Another approach to the problem of blow-outs
is that disclosed, for example, in U. S. Patent No.
4,046,062 wherein separate hold-down sleeves are
employed to clamp the lugs into sealing engagement
20 with the partition wall aperture prior to and
during the extrusion-fusion process. After clamping,
metal is extruded until contact is made, electric
current is passed through the extruded metal to melt
it, and, under the continuing force of the electrodes,
25 metal is caused to flow into any voids in the
aperture while, at the same time, extruding more
metal out of the lugs into the aperture until the
aperture is packed fulI of lug metal.
In U. S. Patent No. 3,869,316 a similar
33 extrusion-fusion system is disclosed wherein high
density polyurethane pads are provided around each
of the electrodes to clamp the lugs tightly against
the walls of the intercell connection during the
extrusion, fusion and cooling steps.
In U. S. Patent No. 3,723,699 the problem
of blow-outs or lead expulsion is expressed in a
projection welding context wherein the lugs are pro-
vided with upstanding annular ribs which surround
the hole in the partition wall and are caused to
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~3~
bite into the partition wall, in an attempt to mini-
mize flow and providing a good mechanical key
between the lugs and partition wall, thus mini-
mizing the possibility of xelative sliding movement
5 between the lugs and partition wall.
Accordingly, as seen from the above-described
prior art references, considerable problems have been
experienced with blow-outs, particularly where lead
i5 extruded into the aperture of the partition with
10 the intent of filling the same. Extrusion-fusion
welding processes have nonetheless achieved consid-
erable success in the industry.
Since the development of extrusion-fusion
welding processes, other problems have also been en-
15 countered in controlling the types of welds whichare obtained under actual production conditions in
battery plants. It ha~ long been known, for example,
that variations in such parameters as the electrical
welding current, squeezing pressure, and in the
20 dimensions of the connector lugs and/or the partition
or casing wall thickness has a direct effect on the
quality of the weld. In the past, these parameters
were adjusted and the resulting welds were then
inspected to determine the quality thereof. This
25 adjustment and inspection process continued until
welds meeting the predetermined criteria were
obtained. After this initial set-up procedure,
which can be very time consuming and laborious, an
attempt is then made to maintain these param~ters
30 constant throughout the subsequ~nt production. Un-
fortunately, changes in one or more of these para-
meters during the ensuing produc~ion could have a
detrimental effect on the quality of the welds pro-
duced thereby. In some cases, these welds will tend
35 to overheat and blow out, while in other cases,
cold or incomplete welds may be formed.
Although, as stated above, a n~nber of
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conditions may account for the variability from weld
to weld under conditions, I have found that the con-
dition of the lugs contributes substantially to the
great variability in weld performance. Lugs are
5 typically cast of lead alloys which harden as they
age, and, which during the ~ battery manu-
~ . , .
facturing operations may acquire varyinq surfacecharacteristics. For example~ lugs which are cast
in conventional parts molding machines may have a
10 slight residue of oil or other film which adheres
thereto from the casting machine (as, for example,
films used to aid in release of the parts which are
cast). Those lugs may then age in the ba~tery plant
for varying lenghts of time deoending upon their
15 sequence of use. During storage they may be exposed
to varying quantities of lead oxide dust and/or
other contaminants present in the battery plant, and
may be subjected to various additional contaminants
depending upon the operations employed to fuse
20 those lugs to their respective stra~s. In some battery
manufacturing plants, the lugs may be cast in a
"Cast-on" machine or may be otherwise formed and fused
to the straps with a much lesser degree of aging prior
to final battery assembly. Once associated with the
25 groups, the lugs are particularly prone to contam-
ination as a result of shedding or other direct or
indirect exposure to the active material of their
associated groups or elements. Finally, depending
upon the manufacturing process employed to make the
30 cases, variable contaminations of the lug surfaces
routinely occurs.
Prior art extrusion-fusion techniques, to
the extent they have attempted to control parameters
of surface contamination, tend to rely on sensing
35 the establishment of an electrical current path
through the lugs at or near the completion of the
extrusion process, that is, at the time contact is
created between the lugs within the cellular
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-6-
aperture. Unfortunately, variations in surface
contaminations of the lugs considerably change the
surface resistance of the lugs; therefore, tech-
niques which sense the establishment of a certain
5 de~ree of electrical contact within the aperture
tend to begin the weld cycle relatively earlier or
later depending upon how dirty the lug surfaces are
at their points of contact, i.e., how much lug con-
tact area need be established in order to trigger
10 the weld cycle. Other prior art techniques have
focused upon controlling the pressure of extrusion
to thereby presumably establish a uniform contact
area between the lugs~ regardless o their surfaces
contamination. Due to the variability in aging
15 processes however, and the consequent variations
in the hardness of the lugs to be extruded tdepend-
; ing upon the age of those lugs), close control of
extrusion pressure from weld to weld results in
~ariations of contact area between the lugs.
Other prior art technigues have used
mechanical stops to limit the extrusion of the
extruding apparatus in order to establish a uniform
contact area between the lugs. However, variations
in lug dimensions will effect the contact area
25 thereby rendering this technique less than
satisfactory.
Summary of the Invention
The present invention generally relates to
a modified electrode configuration for use in an
30 extrusion-fusion type of welding system, and more
particularly, a welding system which obviates any
necessity for time consuming, laborious set-up
procedures, variable pressure control, separ~te
clamps, or particular lug or aperture configurations,
35 and which produces an extremely homogeneous weld with
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a uniform grain structure and surprising strength
heretofore unknown and unachievable in battery manu-
facture.
The superior characteristics of the welds
5 (and batteries produced therewith) result from
numerous features incorporated in applicant's novel
electrodes. One such feature is the novel electrode
tip of applicant's invention. Applicant has recog-
nized that the extrusion portion of the electrode,
10 that is, the tip portion which initially upsets the
metal to cause the initial contact thereof within
the a~erture, should be disposed generally away
from a forging portion, that is, a portion which, in
addition to other functions, tends to limit the
15 extrusion of the electrode during the cold extrusion
phase, whereby the degree of metal to me~al contact
t- within the aperture is uniformly limited.
Applicant has also found that ~ pro-
viding an annular forging portion on the electrode
20 surrounding the aperture to forge the lug around
the aperture at least during the aperture-filling
compression process, that the problem of blow-
outs is eliminated and a substantially denser,
stronger, gas-free, homogeneous weld is attained.
2~ In the preferred embodiment, the annular forging
portion is configured with a contacting surface
which is forced into ~he lug in order to create
a sealing zone of high compression lead surrounding
the aperture. The forging portion also includes an
30 inner ~eveled surface which additionally forges
lead adjacent to the high compression sealing zone
towards the central axis of the aperture. The
annular forging portion further acts as a cold
heat sink for lead disposed adjacent to that portion
35 of the electrodes, to prevent the melting of same.
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1~33~87
~8-
Applicant has ound that it is not nec-
essary to use differential pressures during the
initial upsetting and subsequent compression pro-
cesses. Accordingly, far greater lug, partition
S and aperture tolerances are established so that
weld powers, hold-times and hold-pressures
exhibit substantially greater latitudes than here-
tofore exhibited by prior art devices.
Accordingly, a primary object of the
10 present invention is the provision of a novel bat-
cry having intercell welds exhibiting superior
strength and quality.
Another object of the present inven-
tion is the provision of an extrusion-fusion type
15 of apparatus for forming intercell welds through
an aperture in a lead acid storage battery where-
in the degree~metal to metal contact within the
aperture is uniformly limited to a predetermined
magnitude prior to fusion.
A further object of the present in-
vention is the provision of an apparatus for
producing intercell welds in automotive storage
batteries while overcoming attendant problems
with blow-out.
An additional object of the present
invention is the provision of an extrusion-
fusion type of apparatus for forming intercell
welds in a lead acid storage battery wherein
significantly greater lug, paxtition and
30 aperture misalignments may be suitably accom-
modated without re-adjusting to compensate for
same.
These and other o~jects of the present
invention will become apparent from the following
3s more detailed description.
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~33~37
g
Brief Description of the Drawin~s
Figure 1 i5 a perspective view of the
preferred embodiment electrode of the present
invention.
Figure 2 is a cross-section of the por-
tion of a b~ttery showing flat lugs disDosed on
either side of an intercell partition with an
aperture formed therein and with two preferred
embodiment eIectrodes similar to that illustrated
10 in Figure 1 above shown disposed in their standby
positions spaced apart from the lugs and oriented
generally axially with the aperture of ~he part-
ition through which the intercell connection is
to be formed.
Figure 3 is a cross-section similar to
the view shown in Figure ~, wherein the electrodes
have been moved into contact with the lugs and have
begun to extrude portions of those lugs into the
aperture formed in the intercell partition.
Figure 4 is a greatly enlarged cross-
section similar to Figures 2 and 3, wherein the
electrodes have proceeded with the ~orging step
to a point where metal-to-metal contact between
the lugs is established within the aperture and
25 at a point where the contacting surface of the
forging portions of the electrodes have con-
tacted the lugs.
Figure 5 is a cross-section similar to
Figures 2 and 3, wherein fluidization of lead
30 within the aperture has been effected and the
electrodes bought further toqether so that the
molten metal fills the aperture.
Figure 6 is a cross-section simiiar to
Fisures 3-5, wherein the connection is complete
35 and the electrodes have been withdrawn therefrom,
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~3L33987
~10-
showing the completed w~ld configuration.
pe~SDect; ~/e,
Figure 7 is a pF~ Y~væ view of a strap
and lug showing the external appearance of a lug in
which an intercell connection in accordance with the
5 present invention has been made.
Detailed Description of the Drawings
Although specific forms of the invention
have been selected for illustration in the drawings, anJ
the following description is dra~m in specific
10 terms for the purpose of describing these forms of
the invention, this description is not intended to
limit the scope of the invention which is defined
in the appended claims.
Referring now to Figure 1, there is
15 shown the improved electrode generally referred to
as 10. The electrode 10 comprises a conical
extrusion portion 12 having a vertex 14. The
conical extrusion portion 12 is surrounded by a
concentric, circular forging portion 16 having a
20 contacting surface 18, which is more clearly shown
in Figures 2-6. Both the conical extrusion por-
tion 12 and the forging portion 16 are disposed
on one end of a cylindrical hody 20. The conical
extrusion portion 12 is preferably positioned
25 coaxially with the cylindrical body 20 with the
plane of the contacting surface 18 being su~stan-
tially perpendicular to the coincident axes. A
jaw mount 22 is provided on the opposite end of the
cylind~ical body 20 from conical extrusion portion
30 12 and forging portion 16 in order to enable the
electrode to be conveniently mounted on welding jaws
(not shown). As shown more clearly in Figure 2, the
~orging portion includes an outer beveled surace 24
and an inner beveled surface 26 both of which slope
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.,
away from the contacting surface 18. The outer
beveled surface 24 is the result of the inclusion
of a draft on the outer end surface of the forging
portion 16. In the preferred embodiment, the
draft angle is three degrees. The inner beveled
surface 26 terminates in a recess 28, the sur-
face of which is substantially perpendicular to the
axis of the cylindrical body 20~ It has been
empirically determined that the angle of the inner
beveled surface 26 can range between three degrees
and fifteen degrees and still be effective in mini-
mizing weld blow-outs as will be subsequently
described. In the preferred embodiment, the angle
is between five and eight degrees. A surface 27 ex-
tends from the base of the conical extrusion portion 12to the surface of the recess 28 at a draft angle
which, in the preferred embodiment, is equal to
three degrees. The distance between the base of
the conical portion 12 and the surface of the
recess 28 is substantially equal to one-sixteenth
of an inch in the preferred embodiment. The
electrode 10 is constructed of a material having
~od electrical conductivity and hardness character-
istics.
Referring now to Figure 2, there i~ shown
a cross-section of a portion of a battery partition
30 having an aperture 32 formed therein and having
lugs 34 and 36 disposed thereagainst to overlap
aperture 32. The orientation of the electrodes,
designated generally 38 and 40, with respect to the
aperture prior to welding is also illustrated. The
lugs 34 and 36 are shown to comprise generally flat
surfaces which may lie up against the complimentally
opposing surfaces of partition 30. The lugs are
selected to be or a wid~h and height so that precise
alignment with respect to the aperture 32 is not
necessary. The importance of this fact resides in
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paxt upon the fact that each lug 34 and 36 is formed
or cast as part of straps 42 and 44 respectively,
which, although not shown, are welded to a plurality
of battery plates which make up a group of elements
5 of the battery and which, during the assembly pro-
cess, are slipped into the case generally in the
direction shown by arrows A and B in Figure 2, so
that portions of the lugs 34 and 36 overlap the
partition aperture 32.
It will also be noted from ~igure 2 that
the use of lugs 34 and 36 with flat surfaces dis-
posed thereon allow the finished groups to be in-
serted down into the case without fear that any .
particular portion of the lugs will hang up on
15 the partition, and further without the problems
attendant with projection welding techniques for
first getting the groups into the battery cells
and then for positioning the projections in the
apert.ure, as more iully described for those
20 techniques in U. S. Patent No. 3,364,076.
As seen in Figure 2, the electrodes des-
ignated generally 38 and 40 are al.igned substan-
tially coaxially with aperture 32. The conical
extrusion portions 12a and 12b terminate in Yer-
2S texes 14a and 14b for initially contacting thelugs and for extrudiny the same into the aperture
32. The diameter of the base of the conical ex-
trusion portion 12 is substantially equal to the
diameter of the aperture 32. ~owever, when used
30 in a production environment, it may he necessary
to make the dia,meter of the base smaller than the
diameter of the aperture in order to compensate or
misalignment due to production alignment tolerances.
A misalignment; wherein a portion of the conical
35 extrusion portion overlaps a portion of the edge
of the aperture, can cause pinching and plastic
inclusions in the weld which detrimentally affect
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the quality of the weld. Conseauently, the phase
"substantially equal to" is intended -to include
differences in diameters which are necessitated
by practical implementation considerations such
5 as compensation for production alignment toler-
ances. In the preferred emhodiment, when welding
l-hrough an aperture having a diameter substantially
equal to seven-sixteenths of an inch, ~he diame~er
of the base of the conical ex~rusion portion is
10 substan~ly equal to three-eights of an inch.
With a base diameter equal to three-eighths of an
inch, the heigh~ of the vertex 14 should lie
within a range of one-thirty-second of an inch
to three-thirty-seconds of an inch and is prefer-
15 ably one-sixteen~h of an inch. This range of
heights has been empirically determined and relates
to the functional requirements of the conical
extrusion portion 12 as will be hereinafter described.
The diameter of the concentric, circular
forging portion must be small enough to preclude
overhanging an edge of the lug, but large enough
to prevent overlapping any portion of the aperture
edge in order to minimize blow-outs in the w~ld and
also large enough to stall further cold extrusion
of the lugs, both of which features will be more
fully described hereinafter. The diameter should
fall within the range of one-half to five-eighths
inch. In the preferred embodiment, the diameter of
the circular contacting surface 1& is substantially
equal to five-eighths of an inch. Threaded bores
S0 and 52 are additionally provided in each elec~rode
to receive threaded shafts for mounting ~he electrode
jaws (not shown). As previously stated, the
electrodes should be of sufficient hardness to ex-
hibit acceptable durability during the lead and leadalloy wor~ing processes to which they are to be
subjected. For this purpose, No. 25 beryllium
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copper i5 the preferred material from which the
extrusion ~ortion 12 and forging portion 16 may
be milled or otherwise formed.
Referring now to Figure 3, electrodes
38 and 40 have begun to move together in the dir-
ections of arrows C and D to a point where the
conical extrusion portions l~a and 12b have begun
to contact lugs 34 and 36 into extruded portions
34a and 36a o those lug5 into the aperture 32.
10 The conical shape of the extrusion portion 12
causes the lug material ~o be forced into the
aperture and away from its center, a wedge-like
effect whieh terds to fill the aperture with lug
material. At the position illustrated in Fiyure
3, the contacting surfaces 18a and ]8b of the
forging portions 16a and 16b have not yet begun
to contact the lugs 34 and 36.
Figure 4, which is a areatly enlarged
cross-section similar to Figure 3, illustrates
20 the continued movement of the electrodes together
to a point where the contacting surfaces 18a and
18b of the forging portions 16a and 16b have
contacted the surfaces of the lugs 34 and 36 and
are slightly embedded therein at which point
25 further movement of the electrodes is stalled.
In the preferred embodiment, the contacting sur-
faces become embedded to a depth equal to about
; 0.005 inch before the movement of the electrodes
actually stops. At this point, extruded portions
30 34a and 36a have made the desired degree of con-
tact within the aperture 32. The force supplied
to the electrodes 38 and 40 which urges them in
the directions indicated by the arrows E and F
is of such a magnitude that the extrusion por-
35 tions 12a and 12b will extrude the hardest ofthe lugs to be welded, while at the same time being
insufficient to overcome the stalling effect of the
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~339~37
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forging portions 16a and 16b in the softest of lugs
after the contacting surfaces 18a and 18b of the
forging portions 16a and 16b have made contact with
the surfaces of the lugs 34 and 36, respectively.
5 In the preferred embodiment, with diameter of the
contacting surface being equal to five-eighths of
an inch, this force is substantially equal to 680
pounds. The stalling effect of the forging portion
16a and 16b efectively limits the extrusion move- :~
10 ment of each of the electrodes to the axial distance
measured from the vertex 14 of the extrusion portion
12 to the intersection of the plane containing the
contacting surface 18 with the axis of the electrode.
In the preferred embodiment, this distance is sub-
15 stantially equal to one-half the thickness of the
battery partition 30. When used for welding through
battery partitions having nominal thickness of
0`.070 inch, the contacting surface 18 is .035 inch
from the vertex 14. Accordingly, it may be seen
20 that for this phase of the process, the relative
thickness of the lugs 34 and 36 are immaterial to
the proper functioning of the extruding oortions
12a and 12b and the proper contacting area will
always be formed within the aperture upon engage-
25 ment of the contacting surfaces 18a and 18b withthe lugs 34 and 36, respectively.
A~ter the proper contact area has been
established between the lug portions 34a and 36a,
a current is applied by the electrodes through the
30 lugs in order to fluidize the lead within the
aperture. This current is applied immediately upon
the establishment of the proper metal-to-metal
contact area within the aperture and the movement of
the electrodes together continues in a smooth and
35 uninterrupted fashion as shown in Figure 5, wherein
it may be seen that ~he forging portions 16a and
16b, in combination with the extrusion portlons 12a
, ~,,
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~3~1~17
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and 12b, have continued to move together in the
directions E and F to force the lead to completely
fill the aperture 32 in the partition 30O In the
preferred embodiment, each electrode continues to
5 move for a distance substantially equal to 0.025
inch.
As previously stated, the relationship
of the height of the conical portion 12 verses the
diameter of its base, a relationship which defines
10 the included ansle or sharpness of the cone, has
been empirically determined. S~ith a base diameter
of 3/8 inch, the sharpest cone has a height of
3f 3~ inch and the flattest has a height of 1/32
inch. It has been found that sharper cones, c~n-
15 not adequately function to follow in and hydraul-
ically fill the aperture with fluidized lead
since the forging portion would bottom out before
the aperture has become filled. This creates voids
or "worm tholes" which have a detrimental effect on
20 the ~-~al-ti~`of the weld. In addition, the-greater
height of the cone causes a deeper de~ression
76 ~see Figure 7) in the lug which would tend to
weaken the completed weld. In addition, it has
been found that flatter oones do not permit the
25 uniform establishment of the proper initial con-
tact area within the aperture. ~lso, an entirely
flat extrusion portion was found to cause plastic
inclusions in the weld a~ well as non-uniform
initial heat contact area.
It should be noted that as the aperture
32 is being filled with lead, the forging portions
16a and 16b are further embedded into the exterior
surfaces of the lugs 34 and 36. In the preferred
embodiment, the contacting surface 18 of each
35 electrode becomes embedded in the lug to a total
depth of approximately 0.030 inch. This penetra~
tion of the contacting surfaces 18a and 18b of the
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~L~3391E~7 C~
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forging portions 16a and 16b into the .surface of the
lugs 34 and 360 respectively, during fluidization of
the lead within the aperture will prevent the expul- ;
sion of molten lead from the aperture, commonly
known as blowout.
At the present time, it is not fully
understood how the forging portions lGa and 16b act
within this environment to eliminate problems of
blowout. It is theorized that the circular con-
tacting surface 18 which surrounds the aperture pro-
duces an annular zone of high compression lead which
acts as a seal preventing lead expulsion from the
weld zone. It is further theorized that the inner
beveled surface 26 of the forging portion 16, in
acting to form or force that portion of the lug
interiorly adjacent the contacting surface 18
toward the weld zones sets up stresses internally
within the lug which additionally act to confine the
weld nuggets to prevent expulsion. Finally, the
depth of the recess 28 between the extrusion portion
12 and the forging portion 16 is believed to pro-
vide a certain degree of relief for lead squeezed
between the electrodes, and that lead may actually
be forged up into the annular recess 28 in the
electrode rather than be expulsed from the weld
zone.
Referring now in particular to Figure 6
wherein the electrodes 38 and 40 are being with~
drawn in the directions G and H, respectively, to
reveal a finished weld, it may be seen that the
final intercell connection designated genexally 70
is extremely homogeneous and completely lacking the
air pockets or "worm holes" which typify welds pro-
duced by prior art processes. At the present time,
it is also not unde~stood why the apparatus of the
present invention consistently produced weld nug~
gets which, upon sectioning and etchin~ to show
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grain structure, e~hibit an extremely wide weld zone 72 which is
generally disposed in the configuration shown in Figure 6.
In Figure 6 and Figure 7, the final configuration of
the intercell connection produced by the improved electrode of
the present invention is clearly illustrated. This intercell
connection is, as aforesaid, characterized by large uniform weld
nugget 72 which is disposed to completely fill the aperture 32
within partition 30. Annular depressions 74a and 74b which have
been formed by the forging portions 16a and 16b of the electrodes
38 and 40, respectively, are seen encircling the center of the
connection, while central concave, conical depressions 76a and
76b are disposed in the center of the intercell connection.
In order to determine the comparative strengths of the
intercell weld illustrated in Figure 6, the weld produced using
the improved electrodes of the present invention was tested against
conventional welds produced by a conventional "stepped electrode".
Shear tests were conducted on standard lead and antimony lugs which
were welded with similar currents through partition apertures. In
all instances, a three and one-quarter inch air cylinder was uti
lized in order to provide shearing force across the lug on one
side of the partition while the lug on the other side of the par-
tition was held rigidly. The values obtained by these tests rep-
resent the air pressure supplied to the three and one-quarter inch
cylinder, and, accordingly, are proportional to the pounds of shear
force supplled to each intercell connection in order to break the
same. Intercell connections produced using the prior art "stepped
electrodes" are found to shear generally at between 100 to 120
pounds of air pressure. By comparison, intercell connections pro-
duced by the improved electrodes of the present invention generally
~v
~: .,,~
31L~L33~87 C~
--19-
sheared between about 190 to 200 pounds o~ pressure.
Acc~rdingly, use of applicant t S invention enables
B the formation of intercell ~ which are not
sensitive to dimensional irregularities in the
5 lugs to be welded or the precis~ alignment of
those lugs with respect to the aperture through
the intercell partition is to be made.
It will be understood that various
changes in the details, matexials and arrangements
10 of parts which have been herein described and
illustrated in order to explain the nature of
this invention may be made by those skilled in
the art within the principle and scope of the
invention as expressed in the following claims.
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