Ultrasonic Welding Winder Machine for Cylindrical Batteries

An ultrasonic tab welder, useful for welding metal ribbon to metal sheet, has an ultrasonic stack having a horn configured to include a pair of ends between which are one or more upstanding welding stud surfaces and held by a bracket assembly. The bracket assembly includes a horn holder terminating at either end with U-shaped legs holding either end of the horn and an upper U-shaped legs having a generally horizontal piece carrying a strain gauge. A T-shaped assembly mated with the horn holder U-shaped legs that are carried by a U-shaped holder by a pair of downward holder legs. A pair of ball bearing assemblies are captured between the downward holder legs, the upper holder U-shaped legs, and the horn holder up U-shaped legs. The horn upstanding welding stud surfaces conformingly mate with the metal ribbon as it is welded to the metal sheet.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM

Not applicable.

Not applicable.

BACKGROUND OF THE INVENTION

The present disclosure relates to the manufacture of cylindrical batteries and more particularly to an ultrasonic welder for the welding of a flat wire terminals (anode or cathode) to a metal sheet (anode or cathode) for forming cylindrical batteries.

A variety of present day portable/movable electrically powered items from lawn mowers to electric shavers to automobiles to hoverboards to ad infinitum, require batteries for power. A common battery type for those listed and other products rely on the ubiquitous cylindrical battery. We use them in so many products that we take them for granted, especially when it comes to safety.

Yet, these common batteries can fail, resulting in fire and explosions. That risk comes at the battery factory, the carrier transporting the batteries to a distributor, to a store, and finally to an end user. At all of these stages, the is risk for battery failure with consequent fire, explosion, or both. These battery failures were documented by the Consumer Product Safety Commission in a report prepared by the CPSC staff for the International Battery Seminar dated Mar. 27, 2018. A prime culprit for such documented battery failures was due to a poor ultrasonic weld of an anode/cathode to the battery foil. The welding head (horn) did not always result in complete welds across the horn resulting in short circuits and other failure modes including, for example, over-welded tabs, which result in metallic spikes that can punch through the separator material and short-circuit the anode and cathode and improperly aligned welding horns that can cause under-welded and over-welded connections on opposite ends of the tab weld.

It is to such safety issue that the present invention is addressed.

BRIEF SUMMARY OF THE INVENTION

A demonstration ultrasonic tab welding machine (10) having a stack assembly (22) is adapted for welding metal ribbon (24, e.g., aluminum or nickel cathode) to a metal sheet (16, e.g., copper foil anode) useful to manufacture cylindrical batteries. In particular, demonstration ultrasonic tab welding machine10is useful for welding Li ion battery anode electrode sheets copper foil and Ni tab onto current collectors to prepare Li-Ion pouch cells and cylinder cell. A holder assembly (23) provides self-leveling between the welding hammers or studs (e.g.,80,84,88, etc.) of the horn (54) and the anvil assembly (20). Such self-leveling feature ensures that all of the ultrasonic welds are complete and uniform.

The holder assembly includes an upside down U-shaped upper bracket assembly (60), the downwardly extending legs of which retain a self-leveling assembly, which includes a U-shaped lower bracket assembly (62) and a generally T-shaped middle holder (64). Between the vertical leg of the middle holder the upper legs of the lower bracket assembly is located a strain gage assembly (66) through which the compressive force of the ultrasonic welding happens.

A pair of roller bearing assemblies (65A,65B) are located between the legs of the upper bracket assembly and both the middle holder and the lower bracket assembly. An adjustable space between the middle holder and the lower bracket assembly is defined, such as by an adjustable screw (76). Each of the roller bearing assemblies define a space between the upper bracket assembly and the middle holder.

The downward legs of the lower bracket assembly terminate with a pair of nodal point retainers (57A-D) that retain the horn. The downward legs of the lower bracket assembly also have a pair of holders (67A,67B) located vertically above the nodal point retainers which rest on horn54for capturing horn54between the nodal point retainers and the holder pairs.

In a general sense the disclosed ultrasonic welding machine has a holder assembly for holding the welding horn and which houses a self-leveling assembly composed of a pair of holders that permit the welding horn to swing front-to-back and side-to-side. The swings are confined to be quite small, but of sufficient swing to ensure that the hammers are in uniform contact with the surfaces to be welded.

The drawings will be described in greater detail below.

DETAILED DESCRIPTION OF THE INVENTION

In order to demonstrate the disclosed ultrasonic tab welder and the unique horn holder assembly, a demonstration machine was constructed. Those skilled in this art will appreciate that tab welder is but one small part of the overall machine that produces terminal welded sandwich assemblies useful in the production of cylindrical batteries. The disclosed demonstration ultrasonic tab welder,10, is shown in isometric view inFIG.1. Atop a table,12, is a frame assembly,14, that supports the various components of machine10. Basically, a feed coil of sheet metal, e.g., copper,16, is pulled by take-up coil,18, across an anvil assembly,20, where an ultrasonic stack assembly,22, ultrasonically welds a metal ribbon,24, fed from a coil,26, to sheet metal16. Stack assembly22is held and positioned by a holder assembly,23. A pneumatic air cylinder assembly,28, moves ultrasonic stack assembly22vertically from a home (up) position downwardly to a welding position and back to its home position. An adjustment knob,30, is provided for pneumatic air cylinder assembly,28. Metal coil16is pulled against resistance provided by an axle assembly,32. A controller (not shown) actuates movement of ultrasonic stack assembly22in registration with ribbon24laying atop coil16for its welding with information from a strain gauge66(shown and described later herein).

Referring additionally toFIGS.2and4, an electric drive motor assembly,34, (e.g., stepper motor, linear actuator, or the like) is seen in driving relationship with take-up coil18. Coil26is carried by a coil support assembly,36, consisting of an arm and stand assembly. The stand of coil support assembly36is topped by a roller assembly,38, for metal ribbon24. Metal ribbon24is pulled by a cylinder assembly, attached is a bracket assembly,42, which is terminated with a clamping mechanism,44. Clamping mechanism44grasps metal ribbon24and unwinds it from coil26. As metal ribbon24is unwound it passes under a dual roller assembly,46, whereby metal ribbon24is straightened to a flat metal ribbon configuration,25, and then moved past frame14. Bracket assembly42returns clamp44to its starting position by cylinder assembly40after the welding process. Thus, metal ribbon24is moved and straightened a discrete distance determined by the throw of cylinder assembly40. As straightened flattened metal ribbon25passes through frame assembly14, it is cut by a cutter mechanism,48, which is powered by a cylinder (pneumatic) assembly,50. An adjustment assembly,51, adjusts the length of metal ribbon25that is cut for ultrasonically welding to metal sheet coil18.

Referring now toFIGS.5and6, it will be observed that as flat metal ribbon25approaches cutter mechanism48, it proceeds under an alignment clamp,52, and then underneath cutter mechanism48. It is to be noted that cutter mechanism48stays in its cutting position as metal ribbon25is ultrasonically welded to metal coil sheet16, whereupon it returns to its up or home position. The cutting operation will be detailed later herein.

Referring now toFIGS.7-9, stack assembly22and holder assembly23are shown in greater detail. Holder assembly23has a pair of upside-down U-shaped brackets,55A,55B,55C, and55D, at either end. All four brackets have set screw assemblies,57A,57B,57C, and57D, for holding either end of a horn,54of stack assembly22. This arrangement of set screws reduces the vibrational transfer to the holder assembly23from stack assembly22. Note that bracket55B with its set screw assembly57B are not shown in the drawings. In addition to horn54, stack assembly22includes a converter,56, and support block,58.

Holder assembly23is composed of an upper U-shaped bracket,60, and a lower U-shaped bracket assembly,62, between which is a middle holder assembly,64. Middle holder assembly64include brackets55A-55D. Between lower bracket assembly62and middle holder assembly64is a strain gauge,66. Adjustable screws,68,70,72, and74, hold the components of holder assembly23together. A vertical adjustable screw,76, also is seen extending between middle holder assembly64and lower bracket assembly62restricting lower bracket assembly62vertical movement.

There are four laterally extending arms and bolt assemblies,63A,63B,63C and63D, that can be seen inFIGS.7and8, that allow limited vertical motion while maintaining parallel orientation of the horn relative to the anvil. Specifically, arm/bolt assemblies each consist of lateral plates have nut/bolt assemblies at either end. One of the same end of each assembly on either side of holder assembly23extends into middle holder64, while the opposite of the same end of each assembly extend into lower bracket62. The arm/bolt assemblies, then secure lower bracket62and middle holder64in position. A pair oppositely disposed stops or restraints,61A and61B, secure U-shaped bracket60and middle holder assembly64, so that that middle holder assembly64is restrained from rotating too far about adjustable screws68and72and keep middle holder assembly64in a vertical position.

Held between the downward extending legs of upper bracket60and lower bracket62/middle holder64are ball bearing assemblies,65A and65B, which each have an upper and a lower ball bearing pair. Upper U-shaped bracket60is secured to middle holder64by adjustable screws68and72that pass-through the upper ball bearings of ball bearing assemblies65A and65B. Adjustable screws70and74pass through the lower set of ball bearings of ball bearing assemblies,65A and65B. It should be understood that any sprag mechanism can be substituted for the useful ball bearing assemblies.

Horn54has hammers80arranged so they are in the center of the longitudinal axis,59A, of horn54or the center between the set screw arrangement57A,57C and57B,57D where the downward force is applied to hammers80through strain gauge66. Lower bracket62can rotate slightly about the center of longitudinal axis59A of horn54through its vertical movement. Horn54also has a transverse longitudinal axis,59B, that is defined by set screw arrangement57A,57B and57C,57D. This arrangement allows slight transverse rotation along longitudinal axis59B through bearing assemblies65A and65B. The various components of holder assembly23are held sufficiently tight to appear as a single unit, but not so tight that slight rotational movement about longitudinal axes of horn54is permitted to self-align horn54.

A variety of horn configurations are shown inFIGS.10-15for use with ultrasonic tab welder10. It will be observed that the welding horn can support multiple upstanding welding hammers for simultaneously ultrasonically welding the metal ribbon to multiple locations on the metal sheet. Moreover, such welding hammers can be contained on both sides of the horn enabling the manufacturer to extend the life of the horn prior to its replacement with a new horn.

Specifically, horn78inFIGS.10and12has 3 hammers,80A,80B, and80C, on its top. An additional 3 hammers, not seen, are carried on the opposite side of horn78. Similarly inFIGS.11and12, horn82carries upstanding hammers,84A,84B,84C, and84D. The horn inFIG.12shows both horns78and82, as their side views would be the same. Horn86inFIG.13shows hammers88A and88B on its top side and hammers90A and90B on the horns bottom side. The number of hammers could be 1, 2, 3, 4, etc. inFIG.13for both the top and the bottom of horn86. Thus, the number of welding hammers can be designed by the user to accommodate the needs.

Elongate hammers or welding surfaces94and98are illustrated inFIGS.14and15for horns92and96, respectively. Such elongated welding surfaces enable the horn to vibrate at a lower frequency. Again, the length of the hammers or welding surface can be varied to suit the user on both the top and bottom of the horns.

Referring now toFIGS.16and17, the ribbon feeding, cutting and welding operation is shown in further detail for its understanding. Holder assembly23for horn54of stack assembly22and cutter assembly48are shown in greater detail for cutting metal ribbon25. Cutter assembly48is in an up or home position inFIG.17, while ribbon25is fed forward under cutter assembly48by cylinder assembly40and clamp44. Cutter assembly48is in its down or cutting position inFIG.18. Alignment clamp52is operated by cylinder53clamping ribbon25while the ribbon is being cut. Horn54, however, remains in its up or home position in bothFIGS.16and17. Cutter assembly48includes a clamp,100in housing102, carrying a blade assembly,104. Clamp100is biased by a spring,106, trapped within housing102. Set screws,108and110, hold the clamp in place to a plunger bracket,103. Blade104also is fastened to plunger bracket103as is cutter assembly48. Plunger bracket103has a slot,105, in it that allows the ribbon25to pass through. The bottom of slot105has a ledge,107, that contacts the end of the ribbon25bending it slightly upwardly when the cutter assembly returns to home position and while being held by clamp52. The bent end of ribbon25then will clear medal sheet16on anvil20when cylinder assembly40with clamp44feeds ribbon25forward over metal sheet16.

Cutter assembly48remains in the down or cutting position during the welding operation, as is illustrated inFIG.18where horn54is seen in contact with ribbon25for its welding to metal sheet16. By remaining in a down or cutting position, cutter assembly48holds cut ribbon25in position with clamp100so that it does not move. This ensures that ribbon25is welded in its intended position. InFIG.20, both horn54and cutter assembly48have returned to their home positions. Clamp52holds ribbon25in place while cylinder assembly40retracts to home position. Clamp52raises to home position, medal sheet16indexes and the ribbon feeding, cutting, and welding process restarts.

While the apparatus, system, and method have been described with reference to various embodiments, those skilled in the art will understand that various changes may be made, and equivalents may be substituted for elements thereof, without departing from the scope and essence of the disclosure. In addition, many modifications may be made to adapt a particular situation or material in accordance with the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure is not limited to the particular embodiments disclosed, but that the disclosure will include all embodiments falling within the scope of the appended claims. In this application all units are in the metric system and all amounts and percentages are by weight, unless otherwise expressly indicated. Also, all citations referred herein are expressly incorporated herein by reference.