CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 62/704,075, filed 17 April 2020, the disclosure of which is incorporated herein in its entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to disposable garments and more specifically, to systems and methods for making disposable garments. More specifically, the invention relates to the bonding of garment layers and to the control and adjustment of the spacing and angling between a bonding device (e.g., horn) and patterned anvil in a bonding assembly.

[0003] In the manufacturing of disposable garments, the fabrication of various components in the garment requires the bonding together of multiple layers and/or materials. For example, multiple web materials (e.g., non-woven fabric layers) and/or elastics may be bonded together to form a garment component, such as a diaper chassis. For forming bonds between these layers/materials, a bonding apparatus or assembly may utilize, ultrasonic, thermal, or pressure bonding, for example.

[0004] With regard to the use of ultrasonic energy for bonding layers/materials of a disposable garment, ultrasonic energy is concentrated at specific bond points where frictional heat bonds non-woven fabric of the garment layers. An ultrasonic bonding system contains at least one patterned anvil that communicates with at least one ultrasonic horn. The patterned anvil contains a predetermined pattern created by raised regions on the anvil. The ultrasonic horn contains an ultrasonic emitting assembly. Layers of non-woven fabric, which may or may not contain additional garment components, are passed between the patterned anvil and the ultrasonic horn. The layers contact the raised pattern on the patterned anvil. While in contact with the raised pattern, the layers pass through an ultrasonic emission created by the ultrasonic horn. The ultrasonic emission increases the vibrations of the particles in the non-woven garment, thus increasing the temperature of the particles in the non-woven garment. The increased temperatures of the garment particles in the multiple layers of non-woven fabric result in bonding of the multiple layers of non-woven fabric along the raised patterns of the patterned anvil. [0005] The ultrasonic horn should ideally be maintained at a constant and predetermined distance from the layers of non-woven fabric over a cross-machine direction length of the ultrasonic horn. Methods to monitor and control the constant and predetermined distance over the cross-machine direction length of the ultrasonic horn have typically been performed manually by an operator loosening and tightening a series of bolts on the ultrasonic horn. The operator manually loosens the bolts, manually adjusts a gap or distance between the ultrasonic horn and the patterned anvil, and manually adjusts the level of the ultrasonic horn with respect to the patterned anvil. However, this method often results in an ultrasonic horn placement where the distance between the ultrasonic horn and the patterned anvil is not ideal. As a result of this non-ideal gap or distance, the layers of non-woven fabric will experience varied bonding conditions over the cross-machine direction length. Locations where the distance between the ultrasonic horn and patterned anvil may be less than ideal may result in a ‘blow-out’ phenomenon in which in the ultrasonic energy creates a hole through the layers of non-woven fabric. Locations where the distance between the ultrasonic horn and patterned anvil may be less than ideal also may result in the layers of non-woven fabric not becoming bonded together.

[0006] Further, the leveling of the ultrasonic horn and the adjusting of the gap or distance between the ultrasonic horn and patterned anvil is not a singular event. Instead, the adjustment of the gap or distance requires multiple adjustments over the operation of the machine. The machine must be shut down every time the gap or distance between the ultrasonic horn and patterned anvil is adjusted manually and/or the ultrasonic horn is leveled.

[0007] Therefore, a need exists for an automated system and method for adjusting the gap, or distance, between the ultrasonic horn and patterned anvil and for performing leveling of the ultrasonic horn and/or the anvil into a parallel arrangement. A need further exists for such gap adjustment and leveling to be performed while the machine continues to run, with such gap adjustment and leveling being periodically performed during operation of the machine. BRIEF DESCRIPTION OF THE INVENTION

[0008] In accordance with one aspect of the invention, an apparatus for forming bonds on a web comprises an anvil, a bonding device positioned adjacent the anvil and configured to interact with the anvil to form the bonds on the web, one or more actuator assemblies configured to provide a multi-axis adjustment between the bonding device and the anvil; and a closed-loop control system configured to control operation of the one or more actuator assemblies, the closed-loop control system configured to perform a coarse gap control sequence to cause the one or more actuator assemblies to adjust a gap between the bonding device and the anvil, perform a leveling sequence to cause the one or more actuator assemblies to adjust an orientation between the bonding device and the anvil, perform a fine gap control sequence to cause the one or more actuator assemblies to adjust the gap between the bonding device and the anvil at increments smaller than adjustments during the coarse gap control sequence, and hold the gap between the bonding device and the anvil upon completion of the fine gap control sequence, to maintain a constant force between the bonding device and the anvil for forming the bonds on the web.

[0009] In accordance with another aspect of the invention, a method for positioning and orienting a bonding device relative to an anvil in a bonding assembly that operates to form bonds on a web is provided. The method includes controlling one or more actuator assemblies in the bonding assembly via a closed-loop control scheme to provide a multi-axis adjustment between the bonding device and the anvil, wherein providing the multi-axis adjustment comprises adjusting positioning of the bonding device to adjust a gap between the bonding device and the anvil in an initial calibration of the bonding assembly, the adjustment of the initial calibration comprising a coarse gap adjustment to adjust a gap between the bonding device and the anvil and performing an iterative fine-tuning adjustment of the bonding device to adjust the gap between the bonding device and the anvil and an orientation between the horn and the anvil. The method also includes determining force values indicative of interaction of the bonding device with the anvil during the iterative fine-tuning adjustment; and interrupting the iterative fine-tuning adjustment upon a determined force value reaching a predetermined target force value, so as to hold the gap and orientation between the bonding device and the anvil and thereby maintain a constant force between the bonding device and the anvil for forming the bonds on the web. [0010] These and other advantages and features will be more readily understood from the following detailed description of preferred embodiments of the invention that is provided in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings illustrate embodiments presently contemplated for carrying out the invention.

[0012] In the drawings:

[0013] FIG. 1 is a system view of a bonding assembly that includes a closed-loop control system for leveling and gap adjustment between an ultrasonic horn and patterned anvil, according to an embodiment of the invention.

[0014] FIG. 2 is a system view of the bonding assembly of FIG. 1 illustrating the ultrasonic horn and patterned anvil in a non-level or non-parallel arrangement.

[0015] FIG. 3 is a system view of the bonding assembly of FIG. 1 illustrating the ultrasonic horn and patterned anvil in a level or parallel arrangement.

[0016] FIG. 4 is a perspective view of an ultrasonic horn assembly included in an ultrasonic bonding unit, for use in the bonding assembly of FIG. 1, according to an embodiment of the invention.

[0017] FIG. 5 is a side view of the ultrasonic horn assembly of FIG. 4.

[0018] FIG. 6 is a perspective view of multiple ultrasonic horn assemblies included in an ultrasonic bonding unit, for use in the bonding assembly of FIG. 1, according to an embodiment of the invention.

[0019] FIG. 7 is a graphical illustration of a running standard deviation of power output readings taken by the closed-loop control system of FIG. 1 over time.

[0020] FIG. 8 is a flowchart illustrating a method for performing gap control and leveling between an ultrasonic horn and anvil in an ultrasonic assembly via a closed-loop control system, according to an embodiment of the invention. DETAILED DESCRIPTION

[0021] Embodiments of the present invention provide for a method and apparatus for leveling of a bonding device (e.g., ultrasonic horn) and/or patterned anvil in a bonding assembly into a parallel or substantially parallel arrangement and for adjusting the gap, or distance, between the bonding device and the anvil.

[0022] While embodiments of the invention are described here below with respect to an ultrasonic assembly, it is recognized that embodiments of the invention could alternatively be directed to bonding assemblies of other types. That is, bonding systems configured to perform other types of bonding are recognized as being within the scope of the invention, including thermal or pressure bonding, for example, and thus embodiments of the invention are not limited only to ultrasonic bonding. The disclosure set forth here below is detailed and exact to enable those skilled in the art to practice the invention, and the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. The bonding techniques described herein may also be utilized for applications other than disposable sanitary articles, including applications in the packaging and automotive industries as well as other welding applications. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined in the specification.

[0023] With attention to FIGS. 1-3, a bonding apparatus or assembly 10 is illustrated according to an embodiment of the invention. According to an exemplary embodiment, the bonding assembly 10 comprises an ultrasonic assembly that functions to ultrasonically form bonds on one or more web materials and/or elastics, and thus hereafter bonding assembly 10 is referred to as ultrasonic assembly 10. FIG. 1 is provided to generally illustrate the configuration of bonding assembly 10, while FIGS. 2 and 3 are provided to illustrate leveling of a horn and anvil in the ultrasonic assembly 10 from a non-level arrangement (FIG. 2) to a level arrangement (FIG. 3), as will be explained in greater detail below.

[0024] As shown in FIGS. 1-3, the ultrasonic assembly 10 comprises an ultrasonic bonding unit 11 that includes at least one ultrasonic horn assembly 12, and at least one patterned anvil 14 (hereinafter “anvil 14”), along with a closed-loop control system 16. The ultrasonic assembly 10 may be any of a number of known ultrasonic bonding or welding systems, such as a rotary anvil and an ultrasonic blade horn (or rotary horn), also known as a sonotrode, which cooperate with each other to form bonds on one or more web materials and/or elastics (not shown) that is passed between the ultrasonic bonding unit 11 and anvil 14. The ultrasonic bonding unit 11 and anvil 14 are positioned in a spaced relationship relative to one another to facilitate ultrasonically bonding the web materials/elastics. During the bonding process, the web layers are exposed to an ultrasonic emission from the ultrasonic bonding unit 11 that causes the particles in the web layers to vibrate. The ultrasonic emission or energy is concentrated at specific bond points where frictional heat fuses the web layers together without the need for consumable adhesives.

[0025] The ultrasonic bonding unit 11 may include a single ultrasonic horn assembly 12 in communication with a single anvil 14, as shown in FIGS. 1-3. Alternatively, multiple ultrasonic horn assemblies 12 may be in communication with a single anvil 14, a single ultrasonic horn assembly 12 may be in communication with multiple anvils 14, or multiple ultrasonic horn assemblies 12 may be in communication with multiple anvils 14, in various arrangements.

[0026] A more detailed view of ultrasonic bonding unit 11 and the ultrasonic horn assembly 12 included therein is provided in FIGS. 4-5, according to one embodiment. As shown therein, ultrasonic horn assembly 12 includes a holder-actuator arrangement 18 and an ultrasonic stack 20 of components, with the holder-actuator arrangement 18 mechanically coupled to the ultrasonic stack 20 to enable movement thereof relative to the anvil 14 (FIGS. 1-3).

[0027] In the illustrated embodiment, ultrasonic stack 20 includes a converter 22, a booster 24, and a horn 26. The converter 22 receives a high frequency AC current (from a generator 28 included in ultrasonic assembly 10, FIGS. 1-3) that is indicative of a desired operation of the ultrasonic horn assembly 12 and transforms the signal into a mechanical vibration or ultrasonic emission. The ultrasonic emission is amplified via booster 24 and is transmitted to the horn 26. Based on the interaction of the horn 26 and anvil 14, the ultrasonic emission or energy is concentrated at specific bond points, where frictional heat fuses the web layers together. Booster 24 may be omitted in alternative embodiments.

[0028] In the illustrated embodiment, the holder and actuator arrangement 18 includes a mounting plate 30, a movable assembly 32, and a pair of actuator assemblies 34, 36 (i.e., a gap control actuator assembly 34 and a leveling actuator assembly 36) that control movement of the ultrasonic stack 20 (or specific components thereof). The mounting plate 30 may be secured to a base plate 38 on which each of anvil 14 and ultrasonic bonding unit 11 is mounted (FIG. 6), with the mounting plate 30 affixed to the base plate 38 via fasteners or other suitable means. A track 40 is provided on the mounting plate 30 on a surface thereof opposite the surface that is secured to the base plate 38, with the track 40 oriented so as to enable movement of the ultrasonic stack 20 in a direction that modifies the gap between the horn 26 and the anvil 14. According to embodiments, a single track 40 or multiple tracks 40 may be provided on mounting plate 30.

[0029] Movable assembly 32 is positioned adjacent mounting plate 30 and is movable relative thereto to enable movement of the ultrasonic stack 20. The movable assembly 32 includes a slidable plate 42 having slides 44 mounted thereon, a pivot plate 46 secured to the slidable plate 42, and a stop plate 48 that limits linear movement of the movable assembly 32. The slidable plate 42 is mated with the track(s) 40 of mounting plate 30 via slides 44, with the slides 44 being translatable along track(s) 40 to enable linear movement of the movable assembly 32. Pivot plate 46 is secured to slidable plate 42 on a surface thereof opposite tracks 40, with the pivot plate 46 being secured to slidable plate 42 in a manner that allows for rotation of the pivot plate 46 relative thereto. The ultrasonic stack 20 is secured to the opposite surface of the pivot plate 46, such that the ultrasonic stack 20 rotates along with the pivot plate 46 when the pivot plate 46 is rotated and also translates linearly when slidable plate 42 translates. Stop plate 48 is secured to slidable plate 42 and is positioned adjacent one end of mounting plate 30 so as to abut the mounting plate 30. The stop plate 48 functions to limit the linear movement of the movable assembly 32 - i.e., movement of the horn 26 toward the anvil 14 - as the gap control actuator assembly 34 selectively translates the movable assembly 32 to vary the gap between the horn 26 and anvil 14.

[0030] According to an exemplary embodiment, leveling actuator assembly 36 comprises a rotary leveling actuator 50 and a cam mechanism 52. The rotary leveling actuator 50 is coupled to pivot plate 46 via cam mechanism 52 and is operable to cause rotation of the pivot plate 46 in a desired direction and by a desired amount - i.e., yaw control. Rotation of the pivot plate 46 causes a corresponding rotation of ultrasonic stack 20 (and horn 26), such that leveling between the horn 26 and anvil 14 may be performed. Gap control actuator assembly 34 comprises a rotary gap control actuator 54 and a coupling assembly 56. The coupling assembly 56 is connected to rotary gap control actuator 54 on one end thereof and to stop plate 48 on the opposite end thereof, such that actuation of the rotary gap control actuator 54 causes movement of the movable assembly 32. That is, the coupling assembly 56 is configured to convert the rotation of rotary gap control actuator 54 into a linear motion that is transferred to movable assembly 32, such that gap control between the horn 26 and anvil 14 may be performed. According to one embodiment, a spring 58 is included in coupling assembly 56 on the end thereof adjacent stop plate 48, with the spring 58 providing for a finely controlled adjustment of the linear position of the movable assembly 32.

[0031] While ultrasonic horn assembly 12 is described here above as including gap control actuator assembly 34 and leveling actuator assembly 36 to provide linear movement and yaw control, respectively, for the ultrasonic stack 20 and horn 26, it is recognized that ultrasonic horn assembly 12 may include additional actuator assemblies that would provide further controls for movement of the ultrasonic stack 20 and horn 26. According to additional embodiments, ultrasonic horn assembly 12 may be structured to provide/enable up to six degrees of freedom or types of movement - i.e., roll, pitch, yaw rotation, and linear movement in all three axial directions. Thus, it is recognized that configuration and operation of the ultrasonic horn assembly 12 is not limited to the specific embodiment illustrated in FIGS. 3-5.

[0032] Referring now to FIG. 6, an ultrasonic bonding unit 11 is shown according to another embodiment, such as might be employed in an ultrasonic assembly 10 used for side seam bonding, for example. The ultrasonic bonding unit 11 of FIG. 6 includes three ultrasonic horn assemblies 12 provided in a nested arrangement. As shown therein, each ultrasonic horn assembly 12 includes a holder-actuator arrangement 18 and an ultrasonic stack 20 of components, with the holder-actuator arrangement 18 mechanically coupled to the ultrasonic stack 20 to enable movement thereof relative to the anvil 14. Each ultrasonic horn assembly 12 is independently movable relative to the other ultrasonic horn assemblies 12 based on the controlled operation of actuator assemblies 34, 36, such that gap control and leveling may be performed for the ultrasonic stack 20 and horn 26 of each ultrasonic horn assembly 12.

[0033] As shown in FIG. 6, each of the ultrasonic horn assemblies 12 is generally oriented along an x-axis or direction 71 of the bonding assembly 10, while the web being bonded by bonding assembly 10 moves along the y-axis or direction 73, and anvil 14 rotates about a z- axis or direction 75. In each of ultrasonic horn assemblies 12, the respective actuator assemblies 34, 36 therein are aligned on the x-axis 71 along with the remainder of the components of the ultrasonic horn assembly 12, without extending outwardly in the z-direction 75. In the illustrated embodiment, one actuator 34 extends outwardly from an end of the assembly 12, extending out in the x-direction 71, while the other actuator 36 extends upwardly from a top surface of the assembly 12, extending out in the y-direction 73. This orientation/positioning of the actuator assemblies 34, 36 thereby allows for a close nesting of the ultrasonic horn assemblies 12 in the z-direction 75 without interfering with such nesting. This arrangement/orientation of actuator assemblies 34, 36 is contrasted with a traditional arrangement of horn actuator(s), as such actuators are typically positioned/oriented along the same axis as the horn face and axis of rotation of the anvil (i.e., positioned/oriented in the z- direction 75 in FIG. 6) so as to result is a wide set-up that necessitates greater spacing between the horn assemblies. For example, the nested ultrasonic horn assemblies 12 (and horns 26 therein) in FIG. 6 may be spaced apart by a distance of approximately 100mm, while more traditional set-ups require spacing of 160mm or more.

[0034] Referring again now to FIGS. 1-3, and with continued reference to FIGS. 4-5, operation of the closed-loop control system 16 to monitor and adjust a gap 60 between the horn 26 and anvil 14 and to determine and adjust a leveling condition of the horn 26 with respect to the anvil 14 is described in further detail. In performing a gap control function, the position of the horn 26, i.e., a distance thereof from the anvil 14, may be adjusted via operation of gap control actuator assembly 34, so as to vary a size of the gap 60. In performing a leveling function, the orientation of the horn 26 is adjusted such that the facing surfaces of the horn 26 and anvil 14 are parallel (i.e., level) or substantially parallel with one another (e.g., within +/- 5 degrees). As can be seen in FIGS. 2 and 3, in a non-level condition (FIG. 2), a distance D1 between the horn 26 and anvil 14 at a first location is different from a distance D2 between the horn 26 and anvil 14 at a second location, while when in a level condition (FIG. 3), the distances Dl, D2 are equal or substantially equal to each other.

[0035] In the illustrated embodiment, closed-loop control system 16 comprises a programmable logic controller (PLC) 62, a generator 28, and (in one embodiment) one or more sensors 64, 66, 68. The elements/components of the closed-loop control system 16 are in operable communication with each other, with the generator 28 and sensors 64, 66, 68 in operable communication with the PLC 62 along communication lines 70, the generator 28 in operable communication with the ultrasonic horn assembly 12 along a high frequency cable or communication 72, and the PLC 62 in operable communication with the actuator assemblies 34, 36 along a PLC/actuator communication 74. The generator 28, sensors 64, 66, 68, and PLC 62 function to monitor one or more operational parameters of the ultrasonic assembly 10 indicative of interaction of the ultrasonic horn assembly 12 with the anvil 14 and determine a condition of the ultrasonic horn assembly 12, such as a gap distance and leveling condition of the ultrasonic horn assembly 12 with respect to the anvil 14. The PLC 62 then generates and transmits control signals to the actuator assemblies 34, 36 based on the determination of the gap distance and leveling condition, with the control signals controlling operation of actuator assemblies 34, 36.

[0036] According to embodiments of the invention, the determination of the gap distance and leveling condition of the horn 26 and anvil 14 is performed by the PLC 62 based on the measurement of one or operational parameters associated with operation of the ultrasonic horn assembly 12 and/or interaction between the ultrasonic horn assembly 12 and the anvil 14. According to various embodiments, the operational parameter(s) may be measured directly by the generator 28, by sensors 64, 66 positioned on the horn or anvil, or by a separate sensor 68 included on cabling connecting the generator 28 to the ultrasonic horn assembly 12.

[0037] In an exemplary embodiment, closed-loop control system 16 implements a triple loop control scheme for performing gap adjustment and leveling between the horn 26 and anvil 14. The triple loop control scheme may be generally described as including a first control loop in which a coarse gap control sequence is performed to adjust a gap between the horn 26 and the anvil 14, a second control loop in which a leveling sequence is performed to adjust an orientation between the horn 26 and the anvil 14, and a third control loop in which a fine gap control sequence is performed to adjust the gap between the horn 26 and the anvil 14 at increments smaller than the adjustments performed during the coarse gap control sequence. Each of the control loops is described in further detail here below.

[0038] According to an embodiment of the invention, the coarse gap control sequence in the first control loop is performed as an initial step prior to operation of ultrasonic assembly 10 to form bonds on one or more web materials and/or elastics. The positioning of the horn 26 relative to the anvil 14 is incrementally adjusted via coarse adjustment steps where gap control actuator assembly 34 adjusts positioning of horn, with the gap 60 being adjusted until contact between the horn 26 and anvil 14 is detected. Subsequent to contact between the horn 26 and anvil 14, leveling and fine gap adjustments are performed to position the horn 26 relative to the anvil 14 in a desired arrangement.

[0039] In one embodiment for performing the coarse gap adjustment, the generator 28 directly obtains a plurality of operational parameter measurements that are indicative of the operation of the ultrasonic assembly 10 and of a gap or distance 60 of the horn 26 from the anvil 14. The generator 28 provides those measurements to the PLC 62 for comparison thereof and monitoring of the gap/distance 60. The operational parameter measurements may comprise power or frequency, according to an exemplary embodiment, although it is envisioned that other parameters such as capacitance or amplitude, as non-limiting examples, could alternatively be measured. In obtaining power measurements, command signals are initially provided to converter 22 (from generator 28) that are indicative of a desired ultrasonic emission to be output by horn 26, with the converter 22 and (optional) booster 24 transforming the received command signals into a final output to the horn 26 that causes output of the ultrasonic emission. The resulting power or energy (that is transferred to the web layer(s) for the formation of bonds) is dependent on the arrangement of the horn 26 relative to the anvil 14 and may be measured by the generator 28 based on the outgoing current demanded by the horn 26. The gap distance 60 between the horn 26 and the anvil 14 may thus be monitored based on obtained power readings.

[0040] As an alternative to generator 28 directly measuring or monitoring power signals fed back from the ultrasonic horn assembly 12, a dedicated induction sensor 68 (shown in phantom) may instead be positioned on or integrated into the high frequency cable 72 to monitor operation of the ultrasonic horn assembly 12. Such an induction sensor 68 may be used to retrofit an existing ultrasonic assembly 10 (and generator 28) to enable the assembly 10 to perform a determination of the leveling condition of the horn 26 with respect to the anvil 14. In operation, induction sensor 68 measures electrical current values on the high frequency cable 72 in order to identify a power reading/value indicative of the interaction of the horn 26 with the anvil 14. The measured current values - and subsequently derived power values - may then be used to monitor the gap distance 60 between the horn 26 and the anvil 14.

[0041] In another embodiment for performing the coarse gap adjustment, one or more external sensors 64, 66 are provided in/on either the horn 26 or anvil 14 in order to measure one or more operational parameters associated with operation of the ultrasonic assembly 10. In an exemplary embodiment, the external sensors 64, 66 are load cells that operate to measure a force value at the horn 26 that is indicative of the interaction of the ultrasonic horn 26 with the anvil 14. While the load cells 64, 66 are illustrated as being incorporated into horn 26, it is recognized that the load cells 64, 66 could alternatively be incorporated into anvil 14. In operation, the load cells 64, 66 measure force values F indicative of the interaction of the ultrasonic horn 26 with the anvil 14 in order to provide for monitoring the gap distance 60 between the horn 26 and the anvil 14.

[0042] The acquired operational parameter measurements, such as power or force measurements acquired as described above, are provided to the PLC 62 - where the measured operational parameter is analyzed in order to monitor the gap or distance 60 of the horn 26 from the anvil 14. In analyzing the operational parameter measurements, the measurements are monitored as the position of the horn 26 is incrementally adjusted (i.e. the gap 60 is incrementally reduced). The incremental adjustment of the gap 60 may be performed such that positioning of the horn 26 is adjusted in small increments, such as, for example, one or several millimeters per adjustment.

[0043] According to an exemplary embodiment, a running standard deviation of the measured operational parameter is monitored, and contact between the horn 26 and anvil 14 is identified responsive to a spike in the standard deviation of the parameter. FIG. 7 illustrates an example of power signals being monitored by the closed-loop control system 16 over time, with a standard deviation of power output 76 being shown along with noise 78 also present in the measurements. As can be seen in FIG. 7, spikes in the amplitude of the standard deviation of power output 76 occur when the horn 26 and the anvil 14 come into contact, such that this contact between the horn 26 and anvil 14 is easily identified. While a running standard deviation of power output 76 is illustrated in FIG. 7 as the monitored operational parameter, it is recognized that a similar standard deviation of frequency or force could instead be monitored, according to other embodiments of the invention.

[0044] Upon completion of the coarse gap adjustment performed in the first control loop, the leveling sequence of the second control loop is initiated. As with performing coarse gap control in the ultrasonic assembly 10, the generator 28 may measure power values indicative of the interaction of the horn 26 with the anvil 14 (or frequency or force) or, alternatively, other sensors - i.e., external sensors 64, 66 or induction sensor 68 - may measure operational parameter values indicative of the interaction of the horn 26 with the anvil 14, in order to provide for a determination of an ideal gap distance 60 between the horn 26 and the anvil 14.

[0045] In one embodiment, the generator 28 directly measures power values associated with, or correlated to, the interaction of the horn 26 with the anvil 14. The generator 28 acquires a plurality of power readings that are indicative of the operation of the ultrasonic horn assembly 12 and of a leveling condition of the horn 26 with respect to the anvil 14. The generator 28 provides those measurements to the PLC 62 for comparison thereof and determination of the leveling condition. More specifically, the PLC 62 compares a plurality of power readings in order to identify a maximum power value that corresponds to a level or parallel arrangement between the horn 26 and the anvil 14.

[0046] In performing a method for leveling the horn 26 relative to the anvil 14, the generator 28 begins by measuring a first power value with the horn 26 at a first position or orientation and providing those measurements to the PLC 62. Subsequent to the measurement, the PLC 62 functions to operate the leveling actuator assembly 36 to reorient the horn 26 relative to the anvil 14 - with the leveling actuator assembly 36 causing the horn 26 to rotate in a first direction and to a second position. Upon reorienting the horn 26 to the second position, the generator 28 measures a second power value and provides those measurements to the PLC 62. The PLC 62 then compares the second power value to the first power value and, if the second power value is greater than the first power value, the PLC 62 operates the leveling actuator assembly 36 to reorient the horn 26 relative to the anvil 14 - with the leveling actuator assembly 36 causing the horn 26 to continue rotating in the first direction and to a third position. This sequence of power measurements and rotation of horn 26 in the first direction continues until the measured power value at a new horn position is less than the measured power value at the previous horn position. When the new power value is less than the previous power value, PLC 62 operates the leveling actuator assembly 36 to rotate the horn 26 in a second direction (opposite the first direction), to return the horn 26 to the position where the larger power value was measured.

[0047] Conversely, if upon reorienting the horn 26 to the second position, the measured second power value is less than the first power value, the PLC 62 operates the leveling actuator assembly 36 to successively rotate the horn in the second direction to one or more new positions. At each position, generator 28 monitors a new power value and provides those measurements to the PLC 62. The PLC 62 compares each new power value to the previous power value. As long as the new power value is greater than the previous power value, PLC 62 continues to rotate the horn in the second direction. If the new power value is less than the previous power value, PLC 62 either maintains the horn 26 in the current position or operates the actuator 32 to rotate the horn 26 in the first direction, to return the horn 26 to the position where the larger power value was measured. This larger power value is referred to hereafter as the maximum power value.

[0048] In general, during a leveling or paralleling operation the PLC 62 will generate commands that operate the leveling actuator assembly 36 to continue to rotate the horn 26 in the same direction as long as a subsequent power value reading/measurement is greater than the previous power value reading/measurement, in order to search for a position or orientation of the horn 26 that provides maximum power - i.e., a level or parallel position. Upon a subsequent power value reading/measurement being less than the previous power value reading/measurement, the PLC 62 will flag the previous position as the level or parallel position and cause the horn 26 to stay in the current orientation or rotate back to the level or parallel position at which the maximum power value was measured. In an instance where the previous and subsequent power values are equal, PLC 62 may cause the horn 26 to stay in the current orientation. Accordingly, adjustment of the horn 26 from a non-level position (FIG. 2) to a position where a surface of the horn 26 is level/parallel with the facing surface of the anvil 14 (FIG. 3) may be achieved.

[0049] While operation of the generator 28 during the leveling sequence of the second control loop is described above as measuring power values from the ultrasonic horn assembly 12, it is recognized that generator 28 could alternatively measure other operational parameters, including frequency, capacitance, or amplitude, as non-limiting examples, in order to determine the leveling condition. Determination of the leveling condition with measurement of any of the parameters would be similar to the method described above, with the PLC 62 comparing a plurality of readings in order to identify a specified parameter value (e.g., maximum value) that corresponds to a level or parallel arrangement between the horn 26 and the anvil 14.

[0050] In another embodiment, sensors 64, 66 are provided in order to measure one or more operational parameters associated with operation of a bonding assembly 10, for purposes of performing leveling in the assembly. As indicated previously, in one embodiment the sensors 64, 66 are load sensors that acquire a force measurement and that are incorporated into horn 26, but it is recognized that the sensors 64, 66 could instead be optical sensors, EMF sensors, strain gauges, temperature sensors, or sonar sensors, for example.

[0051] According to an exemplary embodiment, load cells 64, 66 are provided on horn 26 - with a first load cell 64 in close proximity to a first lateral side of the horn 26 and the second load cell 66 in close proximity to a second lateral side of the horn 26 - such that the load cells 64, 66 are generally on opposing sides of the horn 26. With the load cells 64, 66 positioned in such a manner, the load cells 64, 66 operate to measure a force value at each of the opposing sides of the horn 26 - hereinafter referred to as FI and F2.

[0052] In operation, the load cells 64, 66 measure force values FI and F2 indicative of the interaction of the ultrasonic horn 26 with the anvil 14 in order to provide for a determination of the leveling condition of the horn 26 with respect to the anvil 14. The measured force values FI and F2 are provided to the PLC 62, where comparison of the force values FI and F2 is performed in order to determine the leveling condition.

[0053] The method for leveling the ultrasonic horn 26 relative to the anvil 14 using measured force values begins with the load cells 64, 66 measuring force values FI, F2 with the horn 26 at a first position or orientation and providing these measurements to the PLC 62. Subsequent to the measurements, the PLC 62 then compares the force values FI, F2 to determine if the values are equal or within a predetermined standard deviation of one another. If the force values FI, F2 are equal (or within a predetermined standard deviation of one another), the PLC 62 determines that the horn 26 and anvil 14 are in a level or parallel arrangement, and thus no adjustment of the horn 26 is required. Conversely, if the force values FI, F2 are not equal (or within a predetermined standard deviation of one another), the PLC 62 determines that the horn 26 and anvil 14 are in a non-level arrangement and thus operates the leveling actuator assembly 36 to reorient the horn 26 relative to the anvil 14 - with the leveling actuator assembly 36 causing the horn 26 to rotate in a first direction, from a first position to a second position.

[0054] Upon the horn 26 rotating to the second position, the load cells 64, 66 again measure force values FI, F2 and provide these measurements to the PLC 62. The PLC 62 then compares these force values F 1 , F2 to determine if the values are equal or within a predetermined standard deviation of one another. If the force values F 1 , F2 are still not equal (or within a predetermined standard deviation of one another), the PLC 62 determines that the horn 26 and anvil 14 are in a non-level arrangement and operates the leveling actuator assembly 36 to reorient the horn 26 relative to the anvil 14 - with the leveling actuator assembly 36 causing the horn 26 to continue to rotate in the first direction, from the second position to a third position. The PLC 62 continues to operate leveling actuator assembly 36 in this manner until it is determined that the values FI, F2 are equal or within a predetermined standard deviation of one another - with the horn 26 and anvil 14 in a level or parallel arrangement

[0055] Upon completion of the leveling sequence performed in the second control loop, the fine gap control sequence of the third control loop is initiated. As with performing coarse gap control in the ultrasonic assembly 10, the positioning of the horn 26 relative to the anvil 14 is incrementally adjusted via operation of gap control actuator assembly 34 that causes movement of the horn 26. The positioning of the horn 26 relative to the anvil 14 is incrementally adjusted via fine adjustment steps (i.e., incremental adjustments that are smaller than the coarse adjustment steps) until a desired spacing between the horn 26 and anvil 14 is achieved that provides for a proper bonding force to applied to the webs by ultrasonic assembly 10.

[0056] According to an exemplary embodiment of performing the fine gap control sequence of the third control loop, closed-loop control system 16 operates to perform a gap adjustment between the horn 26 and the anvil 14 by acquiring a plurality of force measurements via load cells 64, 66 that are indicative of the operation of the ultrasonic assembly 10 and of a gap 60 of the horn 26 from the anvil 14. The load cells 64, 66 acquire force measurements at a plurality of different gap distances and provide those measurements to the PLC 62 for comparison thereof and determination of a desired gap/distance 60. The position of the horn 26, i.e., distance thereof from the anvil 14, is incrementally adjusted via operation of gap control actuator assembly 34 responsive to a plurality of comparisons of the force readings by the PLC 62 (such as from a distance Dl, to a distance D2, to a distance D3) until the PLC 62 achieves a predetermined target force value that corresponds to an ideal gap distance 60 between the horn 26 and the anvil 14. That is, gap control actuator assembly 34 moves horn 26 in a direction toward anvil 14 until a gap/distance 60 is set that corresponds with the target force value that is determined to provide/form desirable bonds on the web. The horn 26 is then held in this position during operation of the ultrasonic assembly 10 to enable the formation of bonds on the web of a desired strength.

[0057] In alternative embodiments for performing the fine gap control sequence of the third control loop, closed-loop control system 16 operates to perform a gap adjustment between the horn 26 and the anvil 14 by acquiring a plurality of frequency or power measurements via generator 28 that are indicative of the operation of the ultrasonic assembly 10 and of a gap 60 of the horn 26 from the anvil 14. The generator 28 acquires frequency or power measurements at a plurality of different gap distances and provides those measurements to the PLC 62 for comparison thereof and determination of a desired gap 60. The position of the horn 26 is incrementally adjusted via operation of gap control actuator assembly 34 responsive to a plurality of comparisons of the frequency or power readings by the PLC 62 until the PLC 62 achieves a predetermined target frequency or power value that corresponds to a target force value that is determined to provide/form desirable bonds on the web at an associated gap distance between the horn 26 and the anvil 14. That is, gap control actuator assembly 34 moves horn 26 toward anvil 14 until a gap distance 60 is set that corresponds with the target force value that is determined to provide/form desirable bonds on the web.

[0058] In operation of ultrasonic assembly 10, the leveling sequence of the second control loop and the fine gap control sequence of the third control loop are performed in an iterative loop. That is, upon completion of the coarse gap control sequence of the first control loop during an initial set-up/calibration, the leveling and fine gap control of the second control loop and third control loop are performed in an iterative loop in order to perform an incremental adjustment of ultrasonic assembly 10. For example, in embodiments where the ultrasonic bonding unit 11 includes multiple ultrasonic horn assemblies 12 in a nested arrangement, it is recognized that leveling of the horns 26 may not be performed in a single sequence since tilting a horn 26 (i.e., the ultrasonic stack 20) too much during a single sequence may cause the horn 26 to contact the horn of an adjacent ultrasonic horn assembly 12. Therefore, the leveling and fine gap adjustment may be performed in an iterative loop in order to provide acceptable incremental adjustments of the positioning of horn(s) 26.

[0059] In operation of ultrasonic assembly 10, the leveling and fine gap control of the second control loop and third control loop are performed during continued operation of the ultrasonic assembly 10. That is, upon the horn 26 being leveled relative to the anvil 14 and spaced apart therefrom at a gap 60 that corresponds with a target force value that is determined to provide/form desirable bonds on the web, the positioning/orientation of the horn 26 is monitored during ongoing operation of the ultrasonic assembly 10, so as to provide for adjustment thereof if/when necessary. According to one embodiment, an orientation of the horn 26 could be monitored and an error flag generated to alert an operator when an unlevel condition is identified, with the leveling sequence of the second control loop then being performed to level the horn 26 at a desired time. For example, for a slightly unlevel condition of the horn 26, the leveling sequence may be performed during a pre-defmed reject period of the product or an upcoming pause period of the ultrasonic assembly 10, while for a severely unlevel condition of the horn 26 that creates unacceptable bonds/product, the leveling sequence may be performed immediately.

[0060] Referring now to FIG. 8, and with continued reference to FIGS. 1-5, a method 80 for performing gap control and leveling between the horn 26 of each of one or more ultrasonic horn assemblies 12 and an anvil 14 in an ultrasonic assembly 10, via a closed-loop control system 16, is shown according to an embodiment of the invention.

[0061] The method 80 begins at STEP 82 with the performing of a first control loop in which a coarse gap control sequence to adjust a gap between the horn 26 and the anvil 14 as part of an initial calibration of the ultrasonic assembly 10. In performing the coarse gap control, one or more operational parameters of the ultrasonic assembly 10 are monitored. According to embodiments of the invention, the measurements may be acquired via direct monitoring, measurement, or calculation by the generator 28, by an induction sensor 68 positioned on (or spliced into) the high frequency cable 72 connecting the generator 28 and ultrasonic horn assembly 12, or by external sensor(s) 64, 66 integrated with the horn 26 or anvil 14. The operational parameters monitored by the generator 28 may comprise one of power or frequency, the operational parameter measured by the induction sensor 68 may comprise current, and the operational parameter measured by the external sensors 64, 66 may comprise force, as non-limiting examples.

[0062] In performing the coarse gap control sequence at STEP 82, the PLC 62 causes the gap control actuator assembly 34 to perform a coarse adjustment of the horn 26 in a first direction. The operational parameter is monitored by the PLC 62 as the position of the horn 26 is incrementally adjusted, with a running standard deviation of the measured operational parameter being monitored by the PLC 62, according to an exemplary embodiment. The PLC 62 monitors the running standard deviation of the operational parameter to identify a spike in the standard deviation of the parameter that is indicative of contact being made between the horn 26 and anvil 14. Upon contact between the horn 26 and anvil 14 being identified by the PLC 62, the coarse gap control sequence of the first control loop may be terminated.

[0063] Subsequent to contact between the horn 26 and anvil 14 being identified in STEP 82, method 80 continues to STEPS 84 and 86 with the performing of a second control loop in which a leveling sequence adjusts the orientation between the horn 26 and the anvil 14 and the performing of a third control loop in which a fine gap control sequence adjusts the gap between the horn 26 and the anvil 14, respectively. According to one embodiment, the leveling sequence of the second control loop and the fine gap control sequence of the third control loop are performed in an iterative loop, with incremental adjustments to the orientation and linear positioning of the horn 26 being made over multiple repetitions of STEPS 84 and 86. These incremental adjustments of the positioning of horn 26 may be especially desirable where multiple horns 26 (i.e., multiple ultrasonic horn assemblies 12) are included in the ultrasonic bonding unit 11 iterative loop, in order to prevent contact between adjacent horns 26 when rotating the horns during the leveling sequence.

[0064] In performing the leveling sequence at STEP 84 of the second control loop, a first operational parameter value (e.g., power, frequency, or force) is measured by the generator 28 or other sensors 64, 66 with the horn 26 at a first position or orientation and providing those measurements to the PLC 62. Subsequent to the measurement, the PLC 62 functions to operate the leveling actuator assembly 36 to reorient the horn 26 relative to the anvil 14 - with the leveling actuator assembly 36 causing the horn 26 to rotate in a first direction and to a second position. Upon reorienting the horn 26 to the second position, the generator 28 or other sensors 64, 66 measures a second operational parameter value and provides those measurements to the PLC 62. The PLC 62 then compares the second operational parameter value to the first operational parameter value and, if the second operational parameter value is greater than the first operational parameter value, the PLC 62 operates the leveling actuator assembly 36 to reorient the horn 26 relative to the anvil 14 - with the leveling actuator assembly 36 causing the horn 26 to continue rotating in the first direction and to a third position. This sequence of operational parameter measurements and rotation of horn 26 in the first direction continues until the measured operational parameter value at a new horn position is less than the measured operational parameter value at the previous horn position, in order to search for a position or orientation of the horn 26 that provides maximum power or force. When the new operational parameter value is less than the previous power value, PLC 62 operates the leveling actuator assembly 36 to rotate the horn 26 in a second direction (opposite the first direction), to return the horn 26 to the position where the larger operational parameter value was measured.

[0065] In performing the fine gap control sequence of the third control loop at STEP 86, closed-loop control system 16 operates to perform a gap adjustment between the horn 26 and the anvil 14 by acquiring a plurality of operational parameter measurements (e.g., power, frequency, or force) via generator 28 or sensors 64, 66 that are indicative of the operation of the ultrasonic assembly 10 and of a gap 60 of the horn 26 from the anvil 14. The operational parameter measurements are acquired at a plurality of different gap distances and provided to the PLC 62 for comparison thereof and determination of a desired gap/distance 60 that corresponds to a target force value that provides/forms desired bonds on the web. The position of the horn 26, i.e., distance thereof from the anvil 14, is incrementally adjusted via operation of gap control actuator assembly 34 responsive to a plurality of comparisons of the operational parameter readings by the PLC 62 (such as from a distance Dl, to a distance D2, to a distance D3) until the target force value is achieved.

[0066] Upon an iteration of STEPS 84 and 86 being performed, the method 80 continues to STEP 88 - where a determination is made as to whether the horn 26 and anvil 14 are in an optimized parallel/level arrangement and at a desired gap distance. This determination is made based on the one or more monitored operational parameters (e.g., power, frequency, or force) acquired and analyzed at STEPS 84 and 86 and/or based on an analysis of the force being generated for bond formation on the web material. If it is determined at STEP 88 that the horn 26 and anvil 14 are in an optimized parallel/level arrangement and at a desired gap distance, such that a desired force is being generated for bond formation on the web material, as indicated at 90, then the method proceeds to STEP 92 with the horn 26 being held in position during operation of the ultrasonic assembly 10 to enable the formation of bonds on the web of the desired strength. Conversely, if it is determined at STEP 88 that the horn 26 and anvil 14 are not in an optimized parallel/level arrangement and at a desired gap distance, such that a desired force is not being generated for bond formation on the web material, as indicated at 94, then the method proceeds by looping back to STEPS 84 and 86 where the second and third control loops are repeated in order to provide further leveling and gap control of the horn 26.

[0067] If it is determined at STEP 88 that the horn 26 and anvil 14 are in an optimized parallel/level arrangement and at a desired gap distance, such that the horn 26 is held in position at STEP 92, the method 80 then proceeds with continuing to monitor the positioning/orientation of the horn 26 during ongoing operation of the ultrasonic assembly 10. In continuing to monitor the positioning/orientation of the horn 26, a determination is made at STEP 96 as to whether the horn 26 and anvil 14 remain in an optimized parallel/level arrangement and at a desired gap distance. In one embodiment, as part of the determination made at STEP 96, an error flag may be generated to alert an operator when the horn 26 has shifted out of such an optimized parallel/level arrangement with the anvil 14 (i.e., into an unlevel condition). Upon a determination of such a shit occurring, as indicated at 98, the method loops back to STEPS 84 and 86 where the second and third control loops are repeated in order to provide further leveling and gap control of the horn 26. The performing of STEPS 84 and 86 subsequent to this determination 98 may be performed during a pre-defmed reject period of the product or an upcoming pause period of the ultrasonic assembly 10 for a slightly unlevel condition of the horn 26, while for a severely unlevel condition of the horn 26 that creates unacceptable bonds/product, the leveling sequence may be performed immediately. If, conversely, it is determined at STEP 96 that the horn 26 and anvil 14 remain in an optimized parallel/level arrangement and at a desired gap distance, as indicated at 100, then the method proceeds by continuing to monitor the positioning/orientation of the horn 26 during ongoing operation of the ultrasonic assembly 10 and loops back to STEP 96 for another determination of an appropriate positioning/orientation of the horn 26.

[0068] Beneficially, embodiments of the invention thus provide a closed-loop, automated apparatus and method for adjusting the gap, or distance, between the ultrasonic horn and the patterned anvil and for leveling or paralleling the ultrasonic horn and the patterned anvil relative to one another. A multi-axis adjustment of the horn may be performed via a triple loop control scheme in order to provide such gap adjustment and leveling, with it being possible to make such adjustments of the horn positioning while the ultrasonic assembly continues to run. In embodiments where the ultrasonic assembly includes multiple horns, iterative adjustments may be made to the gap control and leveling via the triple loop control scheme - whereby controlled adjustments are made to tilting of the horns that prevent adjacent horns from coming into contact with one another and allow for close nesting of the horns (e.g., 100 mm spacing of horns).

[0069] Therefore, according to one embodiment of the invention, an apparatus for forming bonds on a web comprises an anvil, a bonding device positioned adjacent the anvil and configured to interact with the anvil to form the bonds on the web, one or more actuator assemblies configured to provide a multi-axis adjustment between the bonding device and the anvil; and a closed-loop control system configured to control operation of the one or more actuator assemblies, the closed-loop control system configured to perform a coarse gap control sequence to cause the one or more actuator assemblies to adjust a gap between the bonding device and the anvil, perform a leveling sequence to cause the one or more actuator assemblies to adjust an orientation between the bonding device and the anvil, perform a fine gap control sequence to cause the one or more actuator assemblies to adjust the gap between the bonding device and the anvil at increments smaller than adjustments during the coarse gap control sequence, and hold the gap between the bonding device and the anvil upon completion of the fine gap control sequence, to maintain a constant force between the bonding device and the anvil for forming the bonds on the web.

[0070] According to another embodiment of the invention, a method for positioning and orienting a bonding device relative to an anvil in a bonding assembly that operates to form bonds on a web is provided. The method includes controlling one or more actuator assemblies in the bonding assembly via a closed-loop control scheme to provide a multi-axis adjustment between the bonding device and the anvil, wherein providing the multi-axis adjustment comprises adjusting positioning of the bonding device to adjust a gap between the bonding device and the anvil in an initial calibration of the bonding assembly, the adjustment of the initial calibration comprising a coarse gap adjustment to adjust a gap between the bonding device and the anvil and performing an iterative fine-tuning adjustment of the bonding device to adjust the gap between the bonding device and the anvil and an orientation between the horn and the anvil. The method also includes determining force values indicative of interaction of the bonding device with the anvil during the iterative fine-tuning adjustment; and interrupting the iterative fine-tuning adjustment upon a determined force value reaching a predetermined target force value, so as to hold the gap and orientation between the bonding device and the anvil and thereby maintain a constant force between the bonding device and the anvil for forming the bonds on the web.

[0071] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.