Note: Descriptions are shown in the official language in which they were submitted.
3009~
Background of the inventio_
Reference is made to my prior Canadian Patent No.
1,104,643 issued July 7, 1981 (U.S. Patent 4,166,210 issued
August 28, 1979).
The present invention relates generally to methods of
making intercell welds in electric storage batteries and in
particular to those methods where electrodes are oriented
on either side of a partition or other aperture in a
battery case, lugs or other battery parts are placed over
each side of that aperture, 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 aperture. Such an
apparatus is disclosed in U.S. Patent No. 4,013,864.
It is long 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 interce~l connections, that is, in making the
electrical connections between one battery cell and the
next and/or between the end most battery cells and the
exterior battery terminal of the battery. Since connect-
ions through apertures of this sort, in addition to being
electrical, must provide a liquid seal from cell to cell to
prevent "pumping", some attention has been directed in the
~1~3~
concerning various methods for insuring that an
intercell connector, in addition to providing a
good electrical connection, will also exhibit
good sealing characteristics.
U. S. Patent No. 3,687,734, generally
discloses a connector for electrically connecting
two elements of a storage battery through an
aperture wherein at least one of the connectors
lugs is provided with a passage extending
therethrough. Molten material from an external
10 portion of the connector exists through this
passage during the heat fusion step as a result
of pressure from a heat energy build up. The
patentee attempts by this structure to avoid
the problem of blow outs or lead expulsion
1~ 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 an intercell connections are by a
20 projection welding 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 of the pin
25 material does not exceed the volume defined by
the walls of the opening.
Such attempts inherently involve
tolerance and positioning problems during the
manufacturing and assembly of the parts in
.
~1~3~)04
--3--
battery. More recently, other methods have been
developed for producing battery intercell
electrical connections, which methods have
generally been referred to as "extrusion-~usion"
type method. For example, in ~. S. Patent No.
3,793,086, a method is disclosed wherein flat
surface connector lugs are placed on each side
of the battery partition wall, adjacent an
aperture. The connector lugs are extruded by a
10 pair of opposed electrodes into the aperture
until they meet, whereupon an electrical welding
current is applied. When the welding current
ceases, the connectors are allowed to cool.
As stated in this patent, "it should be
15 emphasized that reduction of the initially
applied shear force during the welding cycle
is essential. If the high applied shear force
is maintained during the welding cycle, molten
lead will be squirted from the welding joint
20 and an imperfect joint can result."
Another approach to the problem of
"blow outs" is that disclosed, for example, in
V. S. Patent No. 4,046,062, wherein separate
hold down slee~es are employed to clamp the lugs
25 into sealing engagement 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 then
passed through the extruded metal to melt it,
~3~
and, under the continuing force of the electrodes,
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 full of lug metal.
In U. S. Patent No. 3,896,316, a
similar extrusion-fusion system is disclosed wherein
high density polyurethane pads are provided around
each of the electrodes to clamp the lugs tightly
10 against the walls of the intercell connection
during the extrusion, fusing the 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
15 are provided with upstanding annular ribs which
surround the hole in the partition wall and are
caused to bite into the partition wall, in an
attempt to minimize flow and to provide a good
mechanical key between the lugs and partition
20 wall, thus minimizing the possibility of relative
sliding mo~ement between the lugs and partition
wall.
Accordingly,as seen from the above
described prior art references, considerable
25 problems have been experienced with hlow outs,
particularly where lead is extruded into the
aperture of the partition with the intent of
filling the same. Extrusion-fusion welding
processes have none the less achieved considerable
~l~3~n~
success in the industry.
Since the development of extrusion-
fusion welding processees, other problems have
also been encountered in controlling the types
S of welds which are obtained under actual
production conditions in battery plants. It
is long been known, for example, that variations
in such parameters as the electrical welding
current, squeezing pressure, and in the
10 dimensions of the connector lugs and/or the
partition or casing wall thickness has a
direct effect on the auality of the weld. In
the past, these parameters were adjusted and
the resulting welds were then inspected to
15 determine th e quality thereof. This 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,
20 an attempt is then made to maintain these
parameters constant throughout the subsequent
production. Unfortunately, changes in one or
more of these parameters during the ensuing
production could have a detrimental effect on
25 the quality of the welds produced thereby. In
some cases, these welds will tend to over heat
and blow out, while in other cases, cold or
incomplete welds may be formed.
1~3~04
--6
. .
Although, as stated above, a number of
conditions may account for the variability from
weld to weld, I have found that the condition of
the lugs contribute substantially to the great
variability in weld performance. Lugs are
typically cast of lead alloys which harden as
they age, and, which during the preceding
battery manufacturing operations may acquire
varying surface characteristics. For exam~le,
10 lugs which are cast in conventional parts
molding machines may have a slight residue of
oil or other film which adheres thereto from
the casting machines (as, for example, films
used to aid in the release of the parts
15 which are cast).
Lugs may also age in the battery plants
for varying lengths of time depending upon their
sequence of use. During storage they may be
exposed to varying quantities of lead oxide
20 dust and/or other contaminents present in the
battery plant, and may be subjected to various
additional contaminents depending upon the
operations employed to fuse those lugs to their
respected straps. In some battery manufacturing
25 plants, the lugs may be cast in a "cast-on"
machine or may otherwise be formed and fused to
the straps with a much lesser degree of aging
prior to the final battery assembly.
~30~4
--7--
Once assoeiated with the groups, the
lugs are partieularly prone to contamination
as a result of shedding or other direet or
indirect exposure to the active material of
there associated groups or elements. Finally,
depending ~oon the manufaeturing proeess
employed to make the cases, variable contaminations
of the lugs surfaces rountinely occurs.
Prior art extrusion-fusion teehniques,
10 to the extent they have attempted to eontrol
parameters of surface contamination, tend to
rely on sensing the establishment of an electrical
current path through the lugs at or near the
completion of the extrusion ~rocess, that is, at
15 the time eontaet is created between the lugs
within cellular aper~ure. Unfortunately,
variations in surface contaminations of the lugs
considerably change the surface resistance of the
lugs; therefore, methods in whieh the establishment
20 of a certain degree of electrical contaet within
the aperture is sensed, tend to begin the weld
cycle relativelv earlier or later depending
upon how dirty the lug surfaces are at their
points of contact, i.e., how much lug contact
25 area need be established in order to trigger the
weld cycle.
Other prior art methods have focused
upon controlling the pressure of extrusion to
thereby presumablv establish a uniform contaet
30 area between the lugs, regardless of there surfaee
eontamination~ Due ~o the variability aging
P~oeessee~ howeve~ and the eonseouent variations
3~
in the hardness of the lugs to be extruded (depending upon
the age of those lugs), close control of the extrusion
pressure from weld to weld results in variations of contact
area between the lugs.
Other prior art methods 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 thereby rendering this technique less than
satisfactory.
Summary of the Invention
The present invention generally relates to a novel
method of extrusion-fusion type welding lead parts through
an aperture in the wall of a battery case, and more
particularly, a method, the use of which obviates the
necessity for time consuming, laborious set up procedures,
variable pressure control, separate clamps, or particular
lug or aperture configurations, and which produces an
extremely homogeneous weld with a uniform grain structure
and surprising strength heretofore unknown and unachievable
in battery manufacture.
~3Q~
More specifically, the invention consists of a method
of welding lead parts through an aperture in the partition
of a battery case utilizing an electrode comprlsing at
least an extruding portion for extruding portions of said
parts to touch within said aperture, and a forging portion
for forging portions of said parts during the welding of
said parts, comprising the steps of: (a) positioning said
parts on opposite sides of said aperture to at least
entirely overlap said aperture; (b) extruding at least a
portion of said parts into said aperture at least until
said forging portion contacts a surface of said part and
said extruded portions touch within said aperture; (c)
limiting the degree of contact between said parts within
said aperture responsive to the degree of contact between
said forging portion and said lead part; (d) passing
current through said parts to melt said portions of said
parts at least within said aperture; (e) compressing at
least said melted portions within said aperture; and (f)
forging unmelted portions of said parts surrounding said
aperture at least during a portion of said compression
step, whereby said lead parts are welded through said
partition of said battery case.
~,~3
-- 10 --
These and other features of embodiments of the present
invention will become apparent from the following more
detailed description.
Brief Descriptio_ of the Drawings
Figure 1 is a perspective view of the preferred
embodiment electrode used in practising the present
invention.
Figure 2 is a cross section of the portion of a battery
showing flat lugs disposed on either side of an intercell
partition with an aperture formed therein and with two
preferred embodiment electrodes similar to that illustrated -
in Figure 1 above shown disposed in stand by positions
spaced apart from the lugs and oriented axially with the
aperture of the partition through which the intercell
lS connection is to be formed.
Figure 3 is a cross section similar to the view shown
in Figure 2, 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 extruding step to a point where metal-to-metal contact
between the lu~s is established within the aperture and at
a point where the contacting surface of the
3~4
~ f` --.,a~--
forging portions of the electrodes have contacted
the lugs.
Fiaure 5 is a cross section similar to
Figures 2 and 3, wherein fluidization of lead
within the aperture has been effected and the
electrodes bought further together so that the
molten metal fills the aperture.
Figure 6 is a cross section similar to
Figures 3-5, wherein the connection is complete
10 and the electrodes have been withdrawn therefrom,
showing the comnleted weld configuration.
Figure 7 is a perspective view of a
strap and lug sho~ing the external apPearanCe of
a lug in which an intercell connection in accordance
15 with the present invention has been made.
Figure 8 is a cross section similar to
Figure 6 wherein the compressive forces exerted
on the lugs in accordance with the method of the
present invention are schematically represented
20 by lines and arrows.
Detailed Description of the Drawings
-
Although specific forms of the invention
have been selected for illustration in the drawings,
the follo~ling description is drawn in specific terms
25 for the purpose of describing these forms of the
invention, this description is not intended to limit
the scoDe of the invention which i5 defined in the
appended claims.
. .
3~04
The present invention relates to a
method of welding lead or lead alloy lugs
through an a~erture in a wall of a battery case,
as for example, through an aperture in an
intercell partition of a battery case to produce
an intercell connection, or alternatively,
through an exterior wall of the batterv case to
form a battery terminal. This method basicallv
comprises positioning the lugs on opoosing
10 sides of the a~erture to least entirelv over-
lap the aperture, extruding at least a portion
of the lugs into the aperture to touch within
the aperture, ~assing current through the lugs
to melt portions of the lugs at least within
15 the aperture, compressing at least the melted
portions within the aperture to fill the
aperture and forging unmelting portions of the
- lugs surrounding the aperture at least durin~
a portion of the com~ression step to prevent
20 blow out of the melted portion during compression.
Referrring now to Figure 1, there is
shown the preEerred embodiment of an electrode
tip, generally referred to as 10, used to carry
out the method of the present invention.
25 Electrode 10 comprises a conical extrusion portion
12 having a vertex 14. ~he conical extrusion
portion 12 is surrounded by a concentric, circular
forging portion 16 having a contacting sur~ace 18,
which is more clearly sho~m in Fi~ures 2-6. Both
30 the conical extrusion portion 12 and the forging
. .
~3~4
~ 3
portion 16 are disposed on one end of a
cylindrical body 20. The conical extrusion
portion 12 is preferablv positioned coaxially
~ith the cylindrical bodv 20 with the plane of
S the contacting surface 18 being substantially
perpendicular to the coincident axes.
A jaw mount 22 is provided on the
opposite end of the cylindrical body 20 from
the conical extrusion portion 12 and forging
10 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 forging portion includes an
outer beveled surface 24 and an inner beveled
15 surface 26 both of which slope away from the
contacting surface 18. The outer heveled
surface 24 results from the inclusion of a
draft on the outer end surface of the forging
~ortion 16. In the preferred embodiment, the
20 draft angle is 3. ?he inner beveled surface
26 terminates in a recess 28, the surface of
which is substantially perpendicular to the
axis of the cylindrical body 20. It has been
imperically cletermined that the angle of ~he
25 inner ~eveled surface 26 can range between
3 and 15 and still be effective in minimizing
weld blow outs as will b~ subseguently described.
In the preferred embodiment, the angle is between
5 and 8 degrees.
/~
A surface 27 extends from the base of
the conical extrusion oortion 12 to the surface
of the recess 28 at a draft angle which, in the
preferred embodiment, is equal to 3. The
distance between the hase of the conical portion
12 and the surface of the recess 28 is substantially
equal to 1/16 o an inch in the preferred embodiment.
The electrode 10 is constructed of a material
having good electrical conductivity and hardness
10 characteristics.
Referring now to Figure 2, there is
shown a cross section of a portion of a battery
partition 30 having an aperture 32 to form therein
and having lugs 34 and 36 disposed there against
15 to overlap the aperture 32. The orientation of the
electrodes, designated generallv 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
20 up against the complimentallv opposing surfaces
of partition 30. The lugs are selected to be of
a width and height so that precise alignment with
respect to the aperture 32 is not necessary. The
importance of this fact resides in part upon the
25 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 pluralitv of
battery plates which make up a group of elements
of the battery and which, during the assenbly
30 process, are slipped into the case generally in
~30~
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 Figure 2 that the use of
lugs 34 and 36 with flat surfaces disposed thereon allow
the finished groups to be inserted down into the case
without fear that any particular portion of the lugs will
hang up on 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 aperture, as more fully
described for those techniques in U.S. Patent ~o. 3,364,076.
As seen in Figure 2, the electrodes designated
generally 38 and 40 are aligned substantially coaxially
with aperture 32. The conical extrusion portions 12a and
12b terminate invertexes 14a and 14b for initially
contacting the lugs and for extruding the same into the
aperture 32. The diameter of the base of the conical
extrusion portion 12 is substantially equal to the diameter
of the aperture 32. However when used in a production
environment, it may be necessary to make the diameter of
the base smaller than the diameter of the aperture in order
to compensa-te for misalignment due to production alignment
tolerances.
..s ~
,
3~
- 16 -
A misalignment, wherein a portion of the conical
extrusion portion overlaps a portion of the edge of the
aperture, can cause pinching and plastic inclusions in the
weld which detrimentally effect the quality of the weld.
Consequently, the phrase "substantially equal to" is
intended to include differences in diameters which are
necessitated by practical implementation considerations
such as compensation for production alignment tolerances.
In the embodiment preferred for carrying out the method of
the present invention, when welding through an aperture
having a diameter substantially equal to 7/16 of an inch,
the diameter of the base of the conical extrusion portion
is substantially equal to 3/8 of an inch, with a base
diameter equal to 3/8 of an inch, the height of the vertex
14 should lie within a range of 1/32 of an inch to 3/32 of
an inch and is preferably 1/16 of an inch. The range of
heights has been emperically determined and relates to the
functional requirements of the conical extrusion portion 12
necessary to carry out the method of the present invention,
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
weld and also large enough to stall further cold
3~4
- 17 --
extrusion of the lugs, both of which features relate to
steps in the method of the present invention and will be
more fully described hereinafter. The d;ameter should fall
within the range of 1/2 to 5/8 of an inch. In the embodi-
ment preferred to carry out the method of the present
invention, the diameter of the circular contacting surface 18
is substantially equal to 5/8 of an inch. As shown in
Figure 2, threaded bores 50 and 52 are additionally provided
in each electrode to receive threaded shafts for mounting
electrode to welding jaws (not shown).
As previously stated, the electrode should be of
sufficient hardness to exhibit acceptable durability during
the lead and lead alloy working processes to which they are
to be subjected. For this purpose, number 25 beryllium copper
is the preferred material from which the extrusion portion 12
and forging portion 16 may be milled or otherwise formed~
Referring now to Figure 3, èlectrodes 38 and 40
have begun to move together in the directions of arrows C
and D to a point where the conical extrusion portions 12a
and 12b have begun to contact lugs 34 and 36 into extruded
portions 34a and 36a of those lugs into the aperture 32. The
conical shape of the extrusion port;on 12 causes the lug
material to be forced into the aperture and away from its
center, a wedge-like
~3
1~
~`..i.
effect which tends to fill the ar,erture with lug
material. This effe~t is further illustrated in
Figure 8 where lines and arrows, collectivelv
referred to as 80, schematically show the
compressive forces exerted on, for example,
lug 36, bv the conical extrusion portion 12 of
the contacting electrode 10. At the position
illustrated in Figure 3, the contacting surfaces
18a and 18b of th e forging rortions 16a and 16b
10 have not yet begun to contact the lugs 34 and 36.
E`igure 4, which is greatl~ enlarged
cross section similar to Figure 3, illustrates
the continued movement of the electrodes
together to a point where the contacting surfaces
15 18a and 18b of the forging portions 16a and 16b
have contacted the surfaces of the lugs 3a and 36
and are sliqhtl~ embedded therein at which point
further movement of the electrodes is stalled.
In the embodiment of the electrodes preferred to
20 carry out the method of the present invention,
the contacting surfaces become embedded to a
depth e~ual to about 0.005" before the movement
of the electrodes actually stops. At this
point, extruded portions 34a and 36a have made
25 the desired degree of contact 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
ex*rusion portions 12a and l~b will extrude the
30 hardest of the lugs to be welded, while at the
~3~)~)4
same time ~eing insufficient to overcome the
stalling effect of the 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.
In the preferred embodiment, with the diameter
of the contacting surface being e~ual to S/8 of
an inch, this force is substantially eoual to
10 680 pounds.
The stallinq effect of the forging
portions 16a and 16b effectively limits the
extrusion movement of each of the electrode
to the axial distance measured from the vertex
15 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 substantially equal
to 1/2 the thickness of the battery partition 30.
20 When used for welding through battery partitions
having nominal thickness of 0.070 inch, the
contacting surface 1~ is 0.035 inch from the vertex
14. Accordingly, it may be seen that for this
phase of the process, the relative thickness of
25 the lugs 34 and 36 are immaterial to the proper
functioning of the extruding portions 12a and 12b
and therefore the proper contacting area will always
be formed within the aperture upon engagement of
the contacting surfaces 18a and 18b with the lugs
30 34 and 36 respectively.
~,o
~;~
After the proper contact area has been
established between the lug portions 34a and 36a,
a current is applied by the electrodes through
the lugs in order to fluidize the lead ~ithin
the aperture. This current is applied immediately
upon the establishment of the proper metal to-
metal contact area within the aperture in the
movement of the electrodes together continues in
a smooth and uninterrupted fashion as shown in
10 Figure 5. There it may be seen that the forging
~ortion 16a and 16b, in combination with the
extrusion portions 12a and 12b, have continued to
move together in the directions ~ and F to force
the lead to completely fill the aperture 37 in
15 the partition 30. In the preferred embodiment,
each electrode continues to move for a distance
substantially equal to 0.025 inch
As previously stated, the relationship
of the height of the conical portion 12 to the
20 diameter of its base, a relationship which defines
the included angle or sharpness of the cone, has
been emperically determined. For the base
diameter of 3/8 of an inch, the sharpest cone has
a height of 3/32 of an inch and the flattest has
25 a height of 1/32 of an inch. It has been found
that sharper cones, cannot adaquately unction to
follow in and hydraulically fill the aperture with
fluidized lead in accordance with the method of
the present invention, since the forging portion
~3~
would bottom out beore the aperture has become
filled. This creates voids or "worm holes"
which have a detrimental effect on the ~uality
of the weld. In addition, the greater height
of the cone causes a deeper depression 76 (see
Figure 7) in a lug which would tend to weaken
the completed weld. In addition, it has been
found that flatter cones do not permit the
uniform establishment of the ~roper initial
10 contact within the aperture. Also, an
entirely flat extrusion portion was found to
cause plastic inclusions in the weld as well
as non-uniform initial heat contact area.
It should be noted that as the
15 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 electrode becomes
20 embedded in the lug for a total depth of
approximately 0.030 inch. This penetration of
the contact surfaces 18a and 18b of the
forging portions 16a and 16b into the surfaces
of the lugs 34 and 36 respectively, durinq
25 fluidization of the lead within the aperture,
will prevent the expulsion of molten lead ~rom
the aperture, commonlv known as "blow-out".
3~
At the present time, it is not fully
understood how the forging portions 16a and 16b
act within this environment to eliminate problems
of blow out. It is theorized that the circular
contacting surface 18 which surrounds the aperture
produces an annular zone of high compression lead
which acts as a seal preventing lead expulsion
from the weld zone. This is schematically shown
by the lines and arrows 82 in Fi~ure 8 which
10 represents the compressive force exerted by the
circular contacting surface 18.
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
15 interiorlv 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. This is
schematically shown bv the lines and arrows 84
20 of Figure 8, which represent the com ressive
forces exerted by the inner beveled surface 26 of
the forging portion 16. Finally, the depth of the
recess 28 between the extrusion portion 12 and the
forging portion 16 is believed to provide a certain
25 degree of relief for leads 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.
11~3~)Q~
,~
Referring now in particular to Figure
6, wherein the electrodes 38 and 40 are being
withdrawn in the direction G and H respectively,
to reveal a finished weld, may be seen that the
final intercell connection designated generally
70 is extremely homogeneous and completely
lacking in the air pockets or "worm holes" which
typify welds produced bv prior art methods. At
the present time, it is also not un~erstood why
10 the method of the present invention consistently
produced weld nuggets which, u~on sectioning and
etching to show grain structure, exhibit an
extremely wide weld zone 72 which is generally
disposed in the configuration shown in Figure 6.
In Figures 6 and 7, the final configuration
of the intercell connection produced in accordance
with the method of the present invention is clearly
illustrated. This intercell connection is, as
aforesaid, characterized by large uniform weld
20 nugget 72 which is disposed to completely fill the
aperture 32 within the 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
25 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 comnarative
strengths of the intercell weld illustrated in
30 Figure 6, the weld nroduced using the method of
the presen~ inventio~ was tested against conventional
~3~0~
.
welds produced by prior art method using a "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 3 1/4 inch air cylinder was
utilized in order to provide shearing force across
the lug on one side of the partition while the lug
on the othex side of the partition was rigidlY
held. The values obtained by these tests represent
10 the air pressure applied to the 3 1/4 inch cylinder
and, accordingly, are proportional to the pounds
of shear force supplied to each intercell
- connection in order to break it. Intercell
connections produced using the prior art method
15 employing the "stepped electrode", are found to
shear generally at between 100 to 120 pounds of
air pressure. By comparison, intercell connections
produced by the method of the present invention
utilizing the nreferred embodiment electrode
20 described therein, generally sheared between
about 190 to 200 pounds of pressure. Accordingly,
the use of applicants inyention enabled the
formation of intercell welds which are not sensitive
to dimensional irregularities in the lugs to be
25 welded or the precise alignment o~ those lugs with
respect to the apertures through which the intercell
connection is to be made.
It will be understood that various changes
in the details, materials and arrangement of parts
30 which have been herein described and illustrated
in order to explain the nature of this invention
ma~ be ~ e by th~se skilled in the art within the
~1~3~
principle and scope of the invention as expressed
in the following claims.
