Ultrasonic welding winding machine for cylindrical battery

Abstract

An ultrasonic tab welding machine for welding a metal strip to a metal sheet has an ultrasonic set having a welding head configured to include a pair of ends between which one or more upright welding stud surfaces are held by a bracket assembly. The bracket assembly includes a horn holder terminating at either end, and an upper U-leg holding either end of the horn, the upper U-leg having a substantially horizontal member carrying a strain gauge. The T-shaped assembly cooperates with a horn holder U-shaped leg that is carried by the U-shaped holder through a pair of downward holder legs. A pair of ball bearing assemblies is captured between the downward retainer leg, the upper retainer U-leg, and the angular retainer upward U-leg. The welding head upright welding stud surface fits consistently with the metal strip when the metal strip is welded to the metal sheet.

Description

[0001] Cross - Reference to Related Applications

[0002] None.

[0003] Statement Regarding Federally Sponsored Research and Development

[0004] Not applicable.

[0005] Names of the Parties to a Joint Research Agreement

[0006] Not applicable.

[0007] Reference to a "Sequence Listing", Table, or Computer Program

[0008] Not applicable.

[0009] Statement Regarding Prior Publication by the Inventor(s) or Co - Inventor(s)

[0010] Not applicable. Background Art

[0011] The present disclosure relates to the manufacture of cylindrical batteries, and more particularly to an ultrasonic welding machine for welding flat wire terminals (anode or cathode) to a metal sheet (anode or cathode) to form a cylindrical battery.

[0012] From lawn mowers to electric razors to cars to hoverboards to an infinity of today's various portable / movable electric items require batteries to power them. The common battery type for those and other products listed relies on the ubiquitous cylindrical battery. We use them in so many products that we take them for granted, especially when it comes to safety.

[0013] However, these ordinary batteries can malfunction, resulting in fires and explosions. The risk comes from battery factories, carriers that ship the batteries to distributors, stores, and finally to end - users. At all these stages, there is a risk of battery malfunction and the consequent fires, explosions, or both. The Consumer Product Safety Commission documented these battery malfunctions in a report prepared by CPSC staff for the International Battery Seminar on March 27, 2018. The main culprit for such documented battery malfunctions is due to poor ultrasonic welding of the anode / cathode to the battery foil. The sonotrode (welding tip) does not always produce a complete weld across the tip, resulting in short - circuits and other failure modes, including for example, over - welded tabs that cause metal spikes that can penetrate the separator material and short - circuit the anode and cathode, and incorrectly aligned welding tips that can result in under - welding and over - welded connections on opposite ends of the tab weld.

[0014] The present invention is directed precisely at such safety problems. Summary of the Invention

[0015] A exemplary ultrasonic tab welding machine (10) having a stack assembly (22) is adapted to weld a metal strip (24, such as an aluminum or nickel cathode) to a metal sheet (16, such as a copper foil anode) for manufacturing a cylindrical battery. In particular, the exemplary ultrasonic tab welding machine 10 can be used to weld a copper foil of a Li-ion battery anode electrode sheet and a Ni tab to a current collector to prepare a Li-ion soft-pack battery and a cylindrical battery. A retainer assembly (23) provides self-leveling between a welding hammer or stud (such as 80, 84, 88, etc.) of a welding head (54) and an anvil assembly (20). This self-leveling feature ensures that all ultrasonic welds are complete and uniform.

[0016] The retainer assembly includes an inverted U-shaped upper bracket assembly (60) whose downwardly extending legs hold a self-leveling assembly that includes a U-shaped lower bracket assembly (62) and a generally T-shaped intermediate retainer (64). A strain gauge assembly (66) is located between the vertical leg of the intermediate retainer and the upper leg of the lower bracket assembly, and the compressive force for ultrasonic welding occurs through the strain gauge assembly (66).

[0017] A pair of roller bearing assemblies (65A, 65B) are located between the legs of the upper bracket assembly and both the intermediate retainer and the lower bracket assembly. An adjustable space between the intermediate retainer and the lower bracket assembly is defined, for example, by an adjustable screw (76). Each of the roller bearing assemblies defines a space between the upper bracket assembly and the intermediate retainer.

[0018] The downward legs of the lower bracket assembly terminate in a pair of node retainers (57A-D) that hold the welding head. The downward legs of the lower bracket assembly also have a pair of retainers (67A, 67B) that are vertically above the node retainers and that rest on the welding head 54 for capturing the welding head 54 between the node retainers and the pair of retainers.

[0019] In a general sense, the disclosed ultrasonic welding machine has a retainer assembly for holding a welding head, and the retainer assembly houses a self-leveling assembly that consists of a pair of retainers that allow the welding head to swing forward and backward and left and right. The swing is limited to be very small, but has enough swing to ensure uniform contact of the hammer with the surface to be welded.

[0020] Brief description of several views of the drawings

[0021] To more fully understand the nature and advantages of the present method and process, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0022] Figure 1 is a front isometric view of an exemplary ultrasonic tab welding machine;

[0023] Figure 2Is an isometric view of the side of a demonstration ultrasonic tab welder at equal intervals, with a part of the frame removed to reveal the details of the ultrasonic welder;

[0024] Figure 3 Is a front isometric view of a demonstration ultrasonic tab welder;

[0025] Figure 4 Is a side view of a demonstration ultrasonic tab welder, with the frame removed to reveal the details of the ultrasonic welder;

[0026] Figure 5 Is Figure 4 An isometric view of an example ultrasonic tab welder;

[0027] Figure 6 Is an enlarged view of the feed mechanism for a demonstration ultrasonic tab welder;

[0028] Figure 7 Is an isometric view of the ultrasonic stack assembly for it;

[0029] Figure 8 Is Figure 7 An end view of the ultrasonic stack assembly;

[0030] Figure 9 Is a cross-sectional view taken along Figure 8 Line 9-9;

[0031] Figure 10 Is an isometric view of an ultrasonic horn with 3 ultrasonic welding areas on either side of the ultrasonic horn;

[0032] Figure 11 Is an isometric view of an ultrasonic horn with 4 ultrasonic welding areas on either side of the ultrasonic horn;

[0033] Figure 12 Is Figure 10 Or Figure 11 A side view of the ultrasonic welding horn;

[0034] Figure 13 Is a side view of an ultrasonic horn with 2 rows of ultrasonic welding areas on both sides of the ultrasonic horn;

[0035] Figure 14 Is an isometric view of an ultrasonic horn with an elongated welding area;

[0036] Figure 15 Is an ultrasonic horn with Figure 15 An isometric view of an ultrasonic horn with an elongated welding area longer than the welding area shown;

[0037] Figure 16is a side view of an exemplary ultrasonic tab bonder showing the wire cutter in an upward or original position and the welding head in an original (non-welding) position;

[0038] Figure 17 is a side view of an exemplary ultrasonic tab bonder showing the wire cutter in a downward or cutting position; and the welding head in an original (non-welding) position;

[0039] Figure 18 is a side view of an exemplary ultrasonic tab bonder showing the wire cutter in a downward or cutting position and the welding head moved downward to a welding position; and

[0040] Figure 19 is a side view of an exemplary ultrasonic tab bonder showing the wire cutter moving upward from its cutting position and the welding head also moving upward from its welding position.

[0041] The drawings will be described in more detail below. DETAILED DESCRIPTION

[0042] To demonstrate the disclosed ultrasonic tab bonder and the unique welding head retainer assembly, a demonstration machine was constructed. Those skilled in the art will understand that the tab bonder is only a small part of the entire machine for producing terminal welding sandwich assemblies for cylindrical battery production. The disclosed exemplary ultrasonic tab bonder 10 is shown in an isometric view in Figure 1 . On top of the worktable 12 is a frame assembly 14 that supports various components of the machine 10. Basically, a feed coil 16 of metal sheet (e.g., copper) is pulled through an anvil assembly 20 by a take-up coil 18, where an ultrasonic stack assembly 22 ultrasonically welds a metal strip 24 fed from a coil 26 to the metal sheet 16. The stack assembly 22 is held and positioned by a retainer assembly 23. A pneumatic cylinder assembly 28 vertically moves the ultrasonic stack assembly 22 from its in-situ (upward) position downward to a welding position and back to its in-situ position. An adjustment knob 30 is provided for the pneumatic cylinder assembly 28. The metal coil 16 is pulled against the resistance provided by a sheave assembly 32. A controller (not shown) actuates the movement of the ultrasonic stack assembly 22 to register it with the strip 24 laid on top of the coil 16 for welding using information from a strain gauge 66 (shown and described later herein).

[0043] Additionally referring to Figure 2 and Figure 4, it is seen that an electric drive motor assembly 34 (e.g., a stepper motor, a linear actuator, etc.) is in a driving relationship with the take-up coil 18. The coil 26 is carried by a coil support assembly 36, which includes an arm and a gantry assembly. The top of the gantry of the coil support assembly 36 is a roller assembly 38 for the metal strip 24. The metal strip 24 is pulled by a cylinder assembly 40, to which a bracket assembly 42 is attached, and the bracket assembly 42 terminates at a clamping mechanism 44. The clamping mechanism 44 grasps the metal strip 24 and unwinds it from the coil 26. As the metal strip 24 is unwound, it passes under a double-roller assembly 46, whereby the metal strip 24 is straightened into a flat metal strip configuration 25 and then moves through the frame 14. After the welding process, the bracket assembly 42 returns the clamp 44 to its starting position via the cylinder assembly 40. Thus, the metal strip 24 is moved and straightened by a discrete distance determined by the stroke of the cylinder assembly 40. As the straightened flat metal strip 25 passes through the frame assembly 14, 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 the metal strip 25 that is cut for ultrasonic welding to the metal sheet coil 18.

[0044] Now refer to Figure 5 and Figure 6 , it will be observed that as the flat metal strip 25 approaches the cutter mechanism 48, it travels under an alignment jig 52 and then under the cutter mechanism 48. It should be noted that when the metal strip 25 is ultrasonically welded to the metal coil sheet 16, the cutter mechanism 48 remains in its cutting position and then returns to its upper or original position. The cutting operation will be described in detail below.

[0045] Now refer to Figures 7 - 9 , the stack assembly 22 and the holder assembly 23 are shown in more detail. The holder assembly 23 has a pair of inverted U-shaped brackets 55A, 55B, 55C, and 55D at either end. All four brackets have fixing screw assemblies 57A, 57B, 57C, and 57D for holding either end of the welding head 54 of the stack assembly 22. This arrangement of the fixing screws reduces the vibration transfer from the stack assembly 22 to the holder assembly 23. Note that the bracket 55B with its fixing screw assembly 57B is not shown in the drawing. In addition to the welding head 54, the stack assembly 22 further includes a converter 56 and a support block 58.

[0046] The retainer assembly 23 consists of a U-shaped upper bracket 60 and a U-shaped lower bracket assembly 62. Between the U-shaped upper bracket assembly 60 and the U-shaped lower bracket assembly 62 is an intermediate retainer assembly 64. The intermediate retainer assembly 64 includes brackets 55A - 55D. Between the lower bracket assembly 62 and the intermediate retainer assembly 64 is a strain gauge 66. Adjustable screws 68, 70, 72, and 74 hold the components of the retainer assembly 23 together. It can also be seen that a vertically adjustable screw 76 extends between the intermediate retainer assembly 64 and the lower bracket assembly 62, thereby restricting the vertical movement of the lower bracket assembly 62.

[0047] There are four laterally extending arms and bolt assemblies 63A, 63B, 63C, and 63D, which can be seen in Figure 7 and Figure 8 and which allow limited vertical movement while maintaining the parallel orientation of the welding head relative to the anvil. Specifically, each arm / bolt assembly consists of a lateral plate having a nut / bolt assembly at either end. One of the same ends of each assembly on either side of the retainer assembly 23 extends into the intermediate retainer 64, while the opposite ends of the same ends of each assembly extend into the lower bracket 62. The arm / bolt assemblies then hold the lower bracket 62 and the intermediate retainer 64 in place. A pair of oppositely disposed stoppers or limiters 61A and 61B fix the U-shaped bracket 60 and the intermediate retainer assembly 64 such that the intermediate retainer assembly 64 is restricted from rotating too far about the adjustable screws 68 and 72 and holds the intermediate retainer assembly 64 in a vertical position.

[0048] Between the upper bracket 60 and the downwardly extending legs of the lower bracket 62 / intermediate retainer 64 are ball bearing assemblies 65A and 65B, each ball bearing assembly having an upper ball bearing pair and a lower ball bearing pair. The upper U-shaped bracket 60 is fixed to the intermediate retainer 64 by adjustable screws 68 and 72 passing through the upper ball bearings of the ball bearing assemblies 65A and 65B. Adjustable screws 70 and 74 pass through the lower ball bearing sets of the ball bearing assemblies 65A and 65B. It should be understood that any wedge mechanism can replace the useful ball bearing assemblies.

[0049] The welding head 54 has hammers 80 which are arranged such that they are centered on the longitudinal axis 59A of the welding head 54 or centered between the fixing screw means 57A, 57C and 57B, 57D, where a downward force is applied to the hammers 80 through the strain gauges 66. The lower bracket 62 can rotate slightly about the center of the longitudinal axis 59A of the welding head 54 by its vertical movement. The welding head 54 also has a transverse longitudinal axis 59B which is defined by the fixing screw means 57A, 57B and 57C, 57D. This arrangement allows for a slight transverse rotation along the longitudinal axis 59B through the bearing assemblies 65A and 65B. The various components of the retainer assembly 23 are held tight enough to present as a single unit, but not so tight as to allow a slight rotational movement about the longitudinal axis of the welding head 54 for self - aligning the welding head 54.

[0050] In Figures 10 - 15 various welding head configurations for use with the ultrasonic tab welding machine 10 are shown. It will be observed that the welding head can support multiple upright welding hammers for simultaneously ultrasonically welding a metal strip to multiple locations on a metal sheet. Additionally, such welding hammers can be included on both sides of the welding head, enabling the manufacturer to extend the life of the welding head before replacing it with a new one.

[0051] Specifically, Figure 10 and Figure 12 the welding head 78 in Figure 11 and Figure 12 has three hammers 80A, 80B and 80C at its top. Three additional hammers (not shown) are carried on the opposite side of the welding head 78. Similarly, in Figure 12 and Figure 13 the welding head 82 carries upright hammers 84A, 84B, 84C and 84D. Figure 13 The welding head in

[0052] shows the welding heads 78 and 82 as their side views would be the same. Figure 14 and 15 The welding head 86 in

[0053] Now referring to Figure 16 and Figure 17, for its understanding, the ribbon feeding, cutting, and welding operations are shown in more detail. The holder assembly 23 and the cutter assembly 48 for the welding head 54 of the stack assembly 22 are shown in more detail for cutting the metal strip 25. The cutter assembly 48 is in the upward or original position in Figure 17 , and the strip 25 is fed forward under the cutter assembly 48 by the cylinder assembly 40 and the clamp 44. The cutter assembly 48 is in its downward or cutting position in Figure 18 . When cutting the strip, the alignment clamp 52 is operated by the cylinder 53 that clamps the strip 25. However, the welding head 54 is held in its upward or original position in both Figure 16 and Figure 17 . The cutter assembly 48 includes a clamp 100 in the housing 102 that carries the blade assembly 104. The clamp 100 is biased by a spring 106 restricted within the housing 102. The fixing screws 108 and 110 hold the clamp in place on the plunger bracket 103. The blade 104 is also fastened to the plunger bracket 103 in the same way as the cutter assembly 48. The plunger bracket 103 has a slot 105 therein that allows the strip 25 to pass through.

[0054] The bottom of the slot 105 has a flange 107 that contacts the end of the strip 25 when the cutter assembly returns to the original position and is held by the clamp 52, causing the strip 25 to bend slightly upward. Then, when the cylinder assembly 40 with the clamp 44 feeds the strip 25 forward onto the metal plate 16, the bent end of the strip 25 will clear the metal sheet 16 on the anvil 20.

[0055] The cutter assembly 48 remains in the downward or cutting position during the welding operation, as shown in Figure 18 , where the welding head 54 is seen contacting the strip 25 to weld it to the metal sheet 16. By remaining in the downward or cutting position, the cutter assembly 48 holds the cut strip 25 and the clamp 100 in place so that it does not move. This ensures that the strip 25 is welded in its intended position. In Figure 20, both the welding head 54 and the cutter assembly 48 have returned to their original positions. The clamp 52 holds the strip 25 in place while the cylinder assembly 40 retracts to the original position. The clamp 52 rises to the original position, the metal sheet 16 indexes, and the strip feeding, cutting, and welding process restarts.

[0056] Although apparatuses, systems, and methods have been described with reference to various embodiments, those skilled in the art will understand that various changes can be made without departing from the scope and essence of the present disclosure, and elements thereof can be replaced with equivalents. In addition, many modifications can be made in accordance with the teachings of the present disclosure to adapt to a particular situation or material without departing from the basic scope of the present disclosure. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but that the present disclosure will include all embodiments falling within the scope of the appended claims. In this application, unless otherwise clearly stated, all units are in the metric system, and all amounts and percentages are by weight. In addition, all citations mentioned herein are expressly incorporated herein by reference.

Claims

1. An ultrasonic tab welding machine (10) for welding a metal strip (25) to a metal sheet (16) for use in manufacturing a cylindrical battery, the improved stack assembly comprising: (a) An ultrasonic stack assembly (22) having a sonotrode (54) configured to include a pair of ends between which are one or more upright welding studs (80, 84, 88), the welding studs being configured to ultrasonically weld the metal strip to the metal sheet; and (b) A retainer assembly (23) for the ultrasonic stack assembly, the retainer assembly (23) comprising: (i) An inverted U-shaped upper bracket assembly (60) having downwardly extending legs; (ii) A U-shaped lower bracket assembly (62) having upwardly extending legs; (iii) A generally T-shaped intermediate retainer (64) having a generally downwardly extending vertical leg; (iv) A strain gauge assembly (66) subjected to the compressive force of ultrasonic welding and located between the generally downwardly extending vertical leg of the intermediate retainer and the upwardly extending leg of the U-shaped lower bracket assembly; (v) A pair of roller bearing assemblies (65A, 65B) located between the downwardly extending legs of the upper bracket assembly and both the intermediate retainer and the lower bracket assembly; (vi) An adjustable screw (76) extending generally vertically adjacent to the intermediate retainer and extending into the lower bracket assembly; (vii) The downward legs of the lower bracket assembly terminating in a pair of node retainers (57A-D) for holding the sonotrode; (viii) Four laterally extending arm and bolt assemblies (63A, 63B, 63C, and 63D) allowing limited vertical movement of the retainer assembly while maintaining the parallel orientation of the sonotrode relative to the anvil, with a pair of laterally extending arm and bolt assemblies extending through the upper bracket assembly and another pair of laterally extending arm and bolt assemblies extending through the generally T-shaped intermediate retainer; (ix) A pair of ball bearing assemblies clamped between the downwardly extending legs of the inverted U-shaped upper bracket assembly (60) and both the upper U-shaped legs of the retainer and the upper U-shaped legs of the sonotrode retainer, whereby the upright welding stud surface of the sonotrode mates with the metal strip in alignment before the metal strip is welded to the metal plate.

2. The ultrasonic welding machine according to claim 1, wherein, The four laterally extending arm and bolt assemblies include a pair of vertically stacked generally laterally extending flat bars having ends through which nut and bolt assemblies are secured.

3. The ultrasonic welding machine according to claim 1, wherein, The sonotrode carries one or more upright welding studs on both of its sides.

4. The ultrasonic welding machine according to claim 1, wherein, A pneumatic cylinder assembly (28) vertically moves the ultrasonic stack assembly downward from its original position to a welding position and moves it back to its original position.

5. The ultrasonic welding machine according to claim 1, wherein, The welded metal strip is continuously fed for ultrasonically welding it to the metal sheet.

6. The ultrasonic welding machine according to claim 1, wherein, A cutter assembly is provided to cut the welded metal strip after the welded metal strip is ultrasonically welded to the metal sheet.

7. A method for ultrasonically welding a metal strip (25) to a metal sheet (16) using an ultrasonic welding machine (10) for manufacturing a cylindrical battery, the method comprising the steps of: (I) Providing an ultrasonic welding machine having a stack assembly, the stack assembly comprising: (a) An ultrasonic stack assembly (22) having a sonotrode (54) configured to include a pair of ends with one or more upright welding studs (80, 84, 88) therebetween, the welding studs being configured to ultrasonically weld a metal strip to a metal sheet; and (b) A retainer assembly (23) for the ultrasonic stack assembly, the retainer assembly (23) including: (i) An inverted U-shaped upper bracket assembly (60) having downwardly extending legs; (ii) A U-shaped lower bracket assembly (62) having upwardly extending legs; (iii) A generally T-shaped intermediate retainer (64) having a generally downwardly extending vertical leg; (iv) A strain gauge assembly (66) subject to the compressive force of ultrasonic welding and located between the generally downwardly extending vertical leg of the intermediate retainer and the upwardly extending leg of the U-shaped lower bracket assembly; (v) A pair of roller bearing assemblies (65A, 65B) located between the downwardly extending legs of the upper bracket assembly and both the intermediate retainer and the lower bracket assembly; (vi) An adjustable screw (76) extending generally vertically adjacent to the intermediate retainer and into the lower bracket assembly; (vii) The downward legs of the lower bracket assembly terminating in a pair of node holders (57A-D) for holding the sonotrode; (viii) Four laterally extending arm and bolt assemblies (63A, 63B, 63C and 63D) allowing limited vertical movement of the retainer assembly while maintaining a parallel orientation of the sonotrode relative to the anvil, with one pair of laterally extending arm and bolt assemblies extending through the upper bracket assembly and the other pair of laterally extending arm and bolt assemblies extending through the generally T-shaped intermediate retainer; (ix) A pair of ball bearing assemblies clamped between the downwardly extending legs of the inverted U-shaped upper bracket assembly (60) and both the upper U-shaped legs of the retainer and the upper U-shaped legs of the sonotrode holder, whereby the upright welding stud surface of the sonotrode mates with the metal strip in alignment before the metal strip is welded to the metal plate; (II) Feeding the metal strip from a coil of the metal strip to a position adjacent to the metal sheet (III) Moving the one or more upright welding studs of the sonotrode to near the metal strip; (III) Actuating the sonotrode, thereby ultrasonically welding the metal strip to the metal sheet; and (IV) Actuating a cutter to cut the metal strip adjacent to the metal strip ultrasonically welded to the metal sheet.

8. The method according to claim 7, which is repeated.

9. The method according to claim 7, wherein a pneumatic cylinder assembly (28) vertically moves the ultrasonic stack assembly downwardly from an original position to a welding position and moves back to its original position.

10. The method according to claim 7, wherein the welding metal strip is continuously fed to ultrasonically weld it to the metal sheet.

11. The method according to claim 7, wherein a cutter assembly is provided, the cutter assembly cutting the welded metal strip after the welded metal strip is ultrasonically welded to the metal sheet.

12. A retainer assembly (23) for retaining an ultrasonic horn adapted for an ultrasonic tab welder, comprising: (i) an inverted U-shaped upper bracket assembly (60) having legs extending downwardly; (ii) a U-shaped lower bracket assembly (62) having legs extending upwardly; (iii) a generally T-shaped intermediate retainer (64) having a generally vertically extending leg; (iv) a strain gauge assembly (66) subject to the compressive force of ultrasonic welding and located between the generally vertically extending leg of the intermediate retainer and the upwardly extending leg of the U-shaped lower bracket assembly; (v) a pair of roller bearing assemblies (65A, 65B) located between the downwardly extending legs of the upper bracket assembly and both the intermediate retainer and the lower bracket assembly; (vi) an adjustable screw (76) extending generally vertically adjacent to the intermediate retainer and extending into the lower bracket assembly; (vii) the downward legs of the lower bracket assembly terminating in a pair of node retainers (57A-D) for retaining the horn; (viii) four laterally extending arm and bolt assemblies (63A, 63B, 63C and 63D) allowing limited vertical movement of the retainer assembly while maintaining the parallel orientation of the horn relative to the anvil, with a pair of laterally extending arm and bolt assemblies extending through the upper bracket assembly and another pair of laterally extending arm and bolt assemblies extending through the generally T-shaped intermediate retainer; (ix) a pair of ball bearing assemblies clamped between the downwardly extending legs of the inverted U-shaped upper bracket assembly (60) and both the upper U-shaped legs of the retainer and the upper U-shaped legs of the horn retainer, whereby the upright welding stud surface of the horn mates consistently with the metal strip before the metal strip is welded to the metal plate.

13. The retainer assembly according to claim 12, wherein, The four laterally extending arm and bolt assemblies include a pair of vertically stacked generally laterally extending flat bars having ends through which nut and bolt assemblies are secured.

14. The retainer assembly according to claim 12, wherein, A pneumatic cylinder assembly (28) vertically moves an ultrasonic stack assembly including the retainer assembly and the ultrasonic horn downwardly from an original position to a welding position and moves it back to its original position.

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