CA1119664A - "extension" to "extrusion" - Google Patents

Abstract

Abstract of the Disclosure The present invention provides a novel electrode construction and application for use in extrusion-fusion type battery intercell welders, which alters the current carrying characteristics of the electrodes and produces a homogeneous weld exhibiting a superior grain structure, higher strength, and superior durability. Each electrode comprises two portions, one of which is of steel and has a substantially higher electrical resistance than the other, which is of berylium copper, the copper electrode peripherally surrounding the steel electrode which is centrally located.

Description

~IL9664 ELECTRODES FOR USE IN T~lE
EXTENSION-FUSION WELDING OF L:EAD PARTS

This application is a division of application Serial No. 299,4~8 filed ~larch 22, 197~.
Bac~ground of the Invention The present invention relates generally to apparatus for making intercell welds in electric storage batteries, and more particularly, to apparatus 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 app.lied generally for the purpose of providing an electrical connection through the aperture. Such an apparatus is sho-rn in U.S. Patent No. 4,013~864.
It has long been known that lead parts on either . _. ,.
side of a partition Irith 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 lead through an aperture is during the formation of intercell connections, that is, in making the , electrical connections bet-reen one battery cell and the next and/or between the endmost battery cells and the 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 "p~mping", some attention has been directed in the art concerning various methods or insuring that an intercell connector, in addition to providing a good electrical connection, will also exhibit good sealing characteristics.
U S. Patent No; 3,6~7,734 generally discloses a connector for electrically connecting two elements of a ~ ' .

.

66~
. ~

storage battery through an aperture wherein at least one of the connector lugs is provided with a passage extending there-through. ~lolten material from an internal portion oE the connector e~its through this passage during -the heat fusion step as a result of pressure ~rom a heat energy build-up. Tlle patentee attempts by this structure to avoid the problem of blol~-outs or lead e~pulsion whic:h has been encountered by many practitioners in this art.
Another attempt to avoid "blow-out" is disclosed in V.S. Patent No. 3,476,611 wherein intercell connections are made by a projection welding process from pins which extend through the partition between two adjacent battery compart-ments, which pins have dimensions such that, when they a~e ~luidized during the process, the volume of the pin material does not e~ceed the volume defined by the walls of the opening.
Such attempts inherently involve tolerance and positioning problems during manufacture and assembly of the parts and battery More recently, other methods have been developed for producing battery intercell electrical connections, which methods have generally been referred to as "extrusion-fusion" type methods. For example, in U.S. Patent No. 3,7g3,086 a method is disclosed wherein flat surfaced connector lugs are placed on each side of the battery partition wall, adjacent an aperture. The connector lugs are e~truded by a pair of opposed electrodes into the aperture until they meet, whereupon an electrical welding current is applied. When the welding -~
current ceases, t:he connector is allowed to cool. U.S. Patent No. 3,793,086 states:
"It should be 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 s~uirted from the welding joint and an imperFect joint can result."
- 3 ~

. .
;- ; , : .
~ . ~ - . .. . ~

6~

Anothcr approach to the problem o~ blow-outs is that disclosed, for example, in Canadian Patent No. 973,522 wllerein separate hold-down sleeves are employed to clamp the lugs into sealing cngagement wi~h the partition wall aperture prior to and during the extrusion-fusion process.
In U.S. Patent No. 4,046,062 issued September 6, 1977, referred to in U.S. Patent No. 3,869,316, a similar process is disclosed wherein two thick plate strap lugs are clamped tightly against an intercell partition having an aperture in it, 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, metal ; is caused to flow into any voids in t~e 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. 3,869,316 a similar extrusion-; ~usion system is disclosed wherein hiuh density polyurethane pads are provided around each of the electrodes to clamp the lugs tightly against the walls of the intercell connection ` 20 during the extrusion, fusion and cooling steps.
In U.S. Patent No. 3,723,699 the problem of blow-outs or lead expu~lsion is expressed in a projection welding context wherein the lugs 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 unwanted flow and providing a good mechanical key between the lugs and partition wall, thus minimizing the possibility of relative sliding movement between the lugs and partition ~all.
~ccordingly, as seen from the above-described prior art re~erences, considerable problems have been experienced 6~
-~ith blow-outs, particularly where lead is e~truded into the aperture of the partition with the inteilt of filling the same.
E~trusion~fusion welding processes have nonetheless achieved considerable s~ccess in the industry.
Summary of the Invention The present invention generally relates to a modi-fied electrode configuration for use in an e~trusion-fusion type of welding system~ and more particularly, a welding system which obviates any necessity for separate clamps, or particular lug or aperture configurations, and which produces an e~tremely homogeneous weld with a uniform grain structure and surprising strength heretofore unkno~n and unachievable in battery manufacture.
To this end the invention provides in an -apparatus having an electrode for electrically fusing lead parts through an aperture in a lead-acid battery case to form a connection therethrough, the improvement wherein said electrode comprises at least two portions, one of which portions has a substantially higher electrical resistance than the other, the portion of higher electrical resistance being generally centrally disposed on said electrode.

966~

These and other features of embodiments of the present invcntion will become apparent from the following detaiIe~
description.
Brief Description of the Drawings Fig. 1 is a perspective view of the preferred embodi-ment electrode of the present invention;
Fig. 2a is a cross-section of the portion of a battery sho-Ying flat lugs disposed on either side on a inter-cell partition lYith an aperture formed therein with two pre-ferred embodiment electrodes similar to that illustrated inFig. 1 above sholm disposed in their standby position spaced apart from the lugs and oriented generally a~ially ~Yith the aperture of the partition through which the intercell connection is to be formed;
Fig. 2b is a cross-section similar to the view sho~n in Fig. 2a wherein the electrodes have been moved in to contact the lugs and begin to force portions of those lugs into the aperture formed in the intercell partition;
~ ig. 2c is a greatly enlarged cross-section similar to Figs. 2a and 2b wherein the electrodes have proceeded with the forcing step to a point where metal to metal contact be-tween the lugs is established within the aperture, and at which point the compression portions of the electrodes have now contacted the lug;

, .

~ . .

~ 6~

Fig. 2d is a cross-section similar to Figs. 2a and 2b wherein fluidi~ation of lead within the aperture has been effected and the electrodes brought further together so that the molten metal fills the hole and the forging portions engage the lug faces;
Fig. 2e is a cross-section similar to Figs. 2a-2d wherein the connection is complete and the electrodes have been withdrawn therefrom, showing the completed weld configuration;
Fig. 2f is a perspective vielr of a strap and lug showing the e~ternal appearance of a lug in which an intercell connection has been made.
Detailed Description of the Preferred Embodiment Although specific forms of the invention have been selected for illustration in the drawlngs, the following description is drawn in specific 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.
The preferred embodiment of the present invention relates to a method of welding lead or lead alloy lugs through an aperture in the 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 altern-atively, through an exterior wall of the battery case to form a battery terminal. This metllod basically compriscs positioning the lugs on opposing sides of ~he aperture to at least entirely overlap the aperture, forcing at least a portion o~ the parts into the aperture to touch within the aperture, passing current through the parts to melt portions of the parts at least within the aperture, com-pressing at least the melted portions within the aperture to fill said aperture and forging unmelted portions of said parts surrounding said aperture at least during a portion of said compression step to prevent blow-out of said melted portion during compression.
The preferred embodiment apparatus of the present invention basically comprises an electrode with forcing, compression and forging portions formed thereon for separately, sequentially performing the above-described steps of forcing~
compressing9 and forging. In the preferred embodiment, the forcing portion of the electrode is composed of a material with a relatively higher resistance than the compression portion of the electrode in order to produce a ~eld nugget of substantially greater volume.
Referring now to the drawings, and in particular to Fig. 1, the preferred embodiment electrode is illustrated in perspective and may be seen to comprise a forcing portion 100, a compression portion 200, and a forging portion 300, each of which are on one end of cylindrical body designated generally 400 in Fig. 1. A jaw mount 402 is provided on the electrode, to enable the electrode to be conventiently mounted on welding jaws. As seen in Fig. 1, in the preferred embodi-ment, the forging portion 300 has an interior surface 304 which is concave or bevelled generally towards the central axis of the electrode, and which surface 304 terminates in ~a ~ 64 ,~
a cutting edge 302 wl1ich is formed between surface 304 and the the outer surface ~06 of the cylindrical body designated generally 400 in the electrode.
Referring now to Fig. 2a, which is a cross~section of a portion of a battery par-tition S00 ha~ing an aperture 502 formed therein and having lugs 50~1 and 506 disposed there-against to overlap aperture 502, the orientation of the electrodes designed generally 600 and 602 ~rith respect to the aperture prior to welding is illustrated. The lugs 504 and 506 are seen to comprise generally flat surfaces which may lie up against the complementally opposin$ surfaces of partition 500. The lugs are selected to be of a width and height so that precise alignment with respect to the aperture is not necessary. The importance of this fact resides in part upon the fact that each lug 504 and 506 is formed or cast as part of straps 50~ and 510 respectively, ~hich, although not shown, are ~relded to a plurality of battery plates ~rl1ich make up a group of elements of the battery and which during the assembly process are slipped into the case generally in the direction shown by arrows A and B in Fig. 2a, so that portions of lugs 504 and 506 overlap the partition aperture~ 502.
It will also be noted from Fig. 2a that the use of lugs 504 and 506 ~rith flat surfaces disposed thereon allow the finished groups to be inserted do~rn into the case without fear that any particular portion of the lugs will hang up on the partition, and further lrithout the problems attendant with projection welding techniques for first getting the groups into the battery cells and then for positioning the projcctions in the aperture, as more fully described for those techniques in U.S. Patent No. 3~364,076.
_ g _" :

.

.

6~a As seen in Fig. 2a, the electrodes designated generally 600 and 602 are aligned substantially coaYially ~ith aperture 502. The forcing portions 604 and 606 of the electrodes are small, substantially cylindrical pieces, the protruding ends of which are formed into points 604a and 606a for initially contacting the lugs and for forcing the same inwardly. Threaded bores 60~ and 610 are additionally provided in each electrode to receive threaded shafts for mounting the electrodes on the appropriate electrode jaws.
In the preferred embodiment, the forcing portions 604 and 606 are relatively better insulators, i.e., have a substanti-ally higher electrical rçsistance than the electrode body.
In particular, the compression portion, forging portion, and forcing portions of the electrode should all be of sufficient hardness to exhibit acceptable durability during the lead and lead alloy working processes to which tlley are to be subjected. For this purpose, berylium copper is the preferred material from which the compression portion 200 ` and forging portion 300 may be milled or otherwise formed, while the forcing portion 100 should preferably be made from a high carbon or carbide steel which is a relatively better insulator than berylium copper. Applicant has found that it is not necessary for the forcing portion 100 to carry a sub-stantial amount of current during the welding process. In one e~perimental test, for example, nylon was substituted or the steel tip utilized in the preferred embodiment to produce welds which, although not as good as those produced by the preferred embodinlent, were nonetheless superior to those heretofore known to the art.
Referring now to Fig. 2b, electrodes 600 and 602 have begun to move togetller in the direction of arrolrs C and - 10-'- . ~

~.
D shol~n in Fig. 2b to a point where forcing portions lO0 havc begun to contact lugs 504 and 506 and to force portions 504a and 506a of those lugs into aperture 502. At the position illustrated in ~ig. 2b, neither the compression portions 200 nor the forging portions 300 have yet begun to contact the lugs.
Fig. 2c, l~hich is greatly enlarged cross-section similar to Fig. 2b illustrates the continued movement of the electrodes together to a point where lug portions 50~a have just touched within aperture 502. At this stage in the pro-cess, it should be noted that compression portions 200 of the electrodes have begun to embed themselves into the surface of the lugs by a distance sufficient to insure that these compression portions 200 will have established a good electrical contact with the exterior surfaces of lugs 504 and 506. =
Accordingly, the leading surface 202, which is substantially perpendicular to the axis of the aperture and which is of a diameter approximately e~ual to the aperture, is spaced behind the leading point of the forcing portion 100 by a distance somewhat less than half of the thickness of the partition through whlch the intercell connection is to be made. Accord-ingly, it may be se~en that for this phase of the process, the relative thic~ness of the lugs 504 and 506 is immaterial to the proper functioning of the forcing portions 100, and the compression portions 200 will always produce a suitable electrical contact with the lug by the time forcing portions 504a and 506a meet wit}lin the partition aperture.
Beginnillg at the tiine that metal to metal contact is established between lug portions 504a and 506a~ a current is applied by the electrodes through the lugs in order to 1uidi~e the lea~ within the aperture. In the prcferred ~ a3L~11.~6~4 r embocliment, current is applied immediately UpO]I thc establish-ment of metal to metal contact wit]lin the aperture and the movement of the electrodes together continues in a smooth and uninterrupted fas]lion as shown in Fig. 2d wherein it may be seen that the compression portions 200 of the electrode~
in combination Wit}l the forcing portions, have continued to move together to force the lead to completely fill the aperture in partition 500. In Fig. 2d, molten lead 700 is shown almost completely filling the aperture just prior to completion of the 10 welding cycle. As the aperture is being filled with lead, but prior to the time that aperture is completely filled with lead, the forging portions 300 come in contact with the e~terior surfaces of lugs 504 and 506 as shown in Fig. 2d.
In the preferred embodiment, it is desired that the forging portions 300 of the electrode not penetrate the lugs so deeply ~as to cause structural weaknesses (or subsequent corrosion) of those lugs, but yet that the leading cutting edge of those forging portions ccntact the exterior surfaces of the electrodes at lcast prior to the complete filling of the aperture under compression as a result of the opposing mo~rement of the remaining portions of the electrode phase.
At the present time, it is not fully understood how l the forging portions 300 act within this environment to eliminate problems of blo~-out. It is theorized that the annular cutting edge 302 which surrounds the aperture produces 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 bevelled or concave surface 304 of the forging portion, in acting to form or force that portion of the lug.interiorally adjacent the cutting edge towards the weld zone sets up stresses internally wit}lin the lug which additionally act to conEine the weld nugget to pre~ent i6~
.

e~pulsion. Finally, the depth of the groove formedbetween the forging portion 300 and compression portion 200 is believed to provide a certain degree of relief for lead squeezed between the electrodes, and that lead may actually be forged up into the annular groove in the electrode rather than be expulsed from the weld zone.
Referring now in particular to Fig. 2e, wherein the electrodes are being withdrawn in the directions E and F
to reveal a finished weld, it may be seen that the final intercell connection designated generally 800 is extremely homogeneous and completely lacks any air pockets or "worm holes" which typify welds produced by prior art processes.
At the present time, it is also not understood why the process and apparatus of the present invention consist-ently produce weld nuggets which, upon sectioning and etching to show grain structure, exhibit an extremely wide weld zone ~0~ which is generally disposed in the configuration shown in Fig. 2e. It is generally theorized that a larger weld zone is encouraged by applying the bulk of current to the weld zone through the peripheral portions of the electrode, and that in prior art devices , where the entire electrode, including the forcing portions, were constructed from the same highly conductive materials that the bulk of the current passir.g through the welds was supplied through the path of least resistance, namely the path between the tips of each forcing portion.
It is believed that by using a somewhat conductive, but substantially rnore resistant material to form the forcing portions of the electode that the current flow is 30 equalized across the face of~the electrodes and that a : - 13 -,. . .
. .
.

substantially larger melting and weld zone is, accordingly, established.
In Fig. 2e and Fig. ~f, the final configuration of the intercell connection produced by the method and apparatus is clearly illustrated. This intercell connection is, as aforesaid, characterized by a large uniform weld nugget 802 which is disposed to completely fill the aperture within partition 500. Annular beads 900 and 902 which have been formed by the forging portion of the electrodes and adjacent to the compression portions of those electrodes are seen encircling the center of the connection, while central depressions 904 and 906 are disposed in the center of the intercell connection and are joined to the annular beads by flat annular rings ~0~ and 910. In order to determine the comparative strengths of the intercell weld illustrated in ~ig. 2e, the weld _ "
produced by the method described above was tested against conventional welds produced by a convention ~erylium cooper "stepped electrode" apparatus. Tests were conducted on standard lead antimony lugs which were welded with similar currents through partition apertures. Since it is known that lead antimony alloys harden as they age r comparative shear testing using conventional shear testing techniques were utilized in order to determine the comparative strengths of "fresh", quenched, and overnight "cured" or "aged" welds. In all instances a 3 1/4 inch air cylinder was utilized in order to provide shearing force across a lug on one side of the partition while the lug on the other side of the partition was held rigidly.
The values obtained by these tests represent the air pressure supplied to the 3 1/4 inch cylinder, and ' . ' ' ' ' 9~6~
~f accordin~ly, are proportional to the pounds o~ shear force applied to eac'n lntercell connection in order to break the same. Fresh intercell connections produced from the conventional stepped electrodes were found to shear generally at between 75 and 80 pounds of air pressure, although certain of the fresh intercell connections tested sheared at values as low as 50 pounds of pressure. By comparison, fresh intercell connections produced by applicant's method and apparatus generally sheared uniformly between about 150 and 152 pounds of pressure. A
cold water quench of the intercell welds produced by applicant's method increased this value to approximately - 160 pounds of pressure required to shear the same.
Intercell connections produced and aged for at least several weeks were tested and it was found that these "aged" or "cured" welds produced from the standard .*
"stepped electrode" sheared at about 180 pounds of pressure. The intercell welds produced by applicant's - method and apparatus, however, sheared at approximately 280 pounds of pressure after aging overnight. Upon further aging, many of these intercell welds approached , 300 to 320 pounds. Of particular importance it was found that when shear did occur in these ranges, the shear did not normally occur at a point within the aperture, but rather that the boundary between the weld nugget and the remaining portion of the lug, thereby indicating that the weld nugget was, itself, extremely homoyeneous; a fact which has been confirmed by sectioning and etching the weld nuggets, as mentioned aforesaid.
Accordingly, applicant's method provides an extremely simple and reliable method of making intercell welds which ..

. . - . : .

~L3~G4 is not sensitive to dimensional irregularities in the lugs to be welded or the precise alignment of those lugs with respect to the aperture through which the intercell partition is to be made.
It will be understood that various changes in the details, materials and arrangement 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.

~ , ...

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. In an apparatus having an electrode for electrically fusing lead parts through an aperture in a lead-acid battery case to form a connection therethrough, the improve-ment wherein said electrode comprises at least two portions, one of which portions has a substantially higher electrical.
resistance than the other, the portion of higher electrical resistance being generally centrally disposed on said electrode.

2. The invention of claim 1, wherein said other portion is a generally peripheral portion surrounding said centrally disposed portion.

3. The invention of claim 1 or 2, wherein said one portion is of steel and said other portion is of berylium copper.

4. The invention of claim 1 or 2, wherein said centrally disposed portion projects from an end of the electrode for exerting a force on said lead parts during operation of the apparatus.