Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-11-30
2003-04-01
Sells, James (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S073100, C156S290000, C156S308400, C156S358000, C156S553000, C156S555000, C156S580200, C156S582000
Reexamination Certificate
active
06540854
ABSTRACT:
BACKGROUND
The present invention relates to apparatus and methods for creating ultrasonic bonds in a web or webs, and/or in discrete workpiece segments, optionally in combination with a web or webs, using ultrasonic bonding apparatus. The invention more particularly concerns apparatus and methods for ultrasonically bonding a web or webs, and/or discrete workpiece segments, optionally in combination with a web or webs, using a rotary ultrasonic horn and a rotary anvil.
Bond strength, where a rotary ultrasonic horn and a rotary anvil are used to bond webs, or discrete workpiece segments is dependent on a variety of factors including horn frequency, horn amplitude, dwell time in the nip, bond pattern, and nip loading. More specifically, the consistency and quality of the bond when using such rotary bonding techniques is significantly dependent on the consistency of the force exerted on the web by the combination of the anvil roll and the rotary ultrasonic horn; the time during which the web is being pressed in the constrictive nip which is dependent in part on the operating speed at the nip; and the nature of the materials being bonded. The consistency and quality of the bonds are also dependent on the frequency and amplitude of the vibrations of the ultrasonic horn.
Consistency and quality of bonds when using conventional rotary ultrasonic bonding methods and apparatus have been particularly variable where the desired bond pattern is intermittently imposed on the material passing through the bonding nip because the nip pressures inherently change in concert with the intermittent nature of the bonding operation.
When nip loading is excessive, so much energy may be applied to the materials being bonded as to burn through or otherwise excessively soften the materials being bonded, as well as to apply so much pressure to the softened materials that the bonds so formed may be weak, and/or may be uncomfortably harsh to the touch of a wearer's skin. In the alternative, excessive loading can physically damage, as by tearing, the material being bonded. Additionally, excessive loading can increase wear or coining and thus damage the ultrasonic horn.
In the past, control of the nip force has evolved from constant force to fixed interference. More specifically, early practice in the art of ultrasonic bonding was to force an anvil against a horn with a fixed, defined load. The anvil rode on the horn much like a train wheel runs on a rail. The force applied was substantially constant regardless of the presence or absence of material in the nip. The constant force of the fixed load design at high force levels tended to cause rapid horn wear.
The next step in the evolution of ultrasonic bonding was to load the anvil roll with high force against a fixed stop and to use the stop to establish interference. In this design, the stop drew a relatively high fraction of the load until material entered the nip; at that point, the greater interference caused by the material drew more of the load as the stop load diminished.
A need exists to develop apparatus and methods for loading a nip to a known force rather than loading to a fixed interference. Similarly, a need exists to develop apparatus and methods for loading a nip including measuring and adjusting a nip load as a direct reading of force rather than as an inferred value from a change in interference.
It is another object of this invention to provide ultrasonic bonding apparatus and methods wherein the bonding apparatus transmits a real-time ongoing and dynamic signal output to apparatus which is designed and configured to automatically adjust nip loading toward a known target load, without ongoing real-time human intervention.
It is yet another object of this invention to provide bonding apparatus and methods wherein a portion of the bonding apparatus can be automatically raised or lowered in response to detected nip loading output until the force applied to the respective portion of bonding apparatus results in desired ultrasonic bond-creating pressure in the nip.
SUMMARY
In a first family of embodiments, the invention comprehends ultrasonic bonding apparatus for creating ultrasonic bonds in sequentially advancing workpiece segments, in a nip defined by a rotary ultrasonic horn mounted for rotation about a first axis, and a rotary anvil roll mounted for rotation about a second axis substantially aligned with the first axis. The anvil roll comprises a width, a circumference, and a bonding portion disposed about at least a portion of the circumference. The ultrasonic bonding apparatus comprises support structure comprising anvil support apparatus and the horn support apparatus. The anvil support apparatus is connected to the anvil roll, and horn support apparatus is connected to the ultrasonic horn. The support structure supports the bonding apparatus from an underlying support. The anvil support apparatus comprises an anvil moving assembly for moving the anvil roll into contact with the ultrasonic horn, and for moving the anvil roll out of contact with the ultrasonic horn. Closed loop control apparatus is connected to one of the anvil support apparatus and the horn support apparatus. The closed loop control apparatus comprises a programmable logic controller, a load cell, and an adjustor. The ultrasonic horn and the anvil roll collectively are mounted and configured such that the ultrasonic horn and the anvil roll can be brought together to define the nip therebetween, wherein the anvil roll and the ultrasonic horn can rotate in common with movement of workpiece segments through the nip. Information output from the load cell triggers the closed loop control apparatus through the programmable logic computer and the adjustor to move the one of the anvil support apparatus and the horn support apparatus toward and away from the other of the anvil support apparatus and the horn support apparatus in automatic and dynamic response to the information output from the load cell, thereby regulating pressure in the nip with ongoing real-time adjustments to distance between the anvil support apparatus and the horn support apparatus without real-time operator intervention.
In preferred embodiments, the load cell is arranged and configured to measure representative nip loads, thereby to define forces generated between the ultrasonic horn and the anvil roll.
In some embodiments, the adjustor comprises a servo motor.
In some embodiments, the invention comprises a load cell conditioner connected to the load cell. The load cell conditioner functions to amplify output from the load cell.
Preferred embodiments can include a back-up roll juxtaposed adjacent the ultrasonic horn, opposite the anvil roll, wherein the back-up roll engages an outer surface of the ultrasonic horn at an engagement locus in alignment with a line extending through extensions of the first and second axes.
In some embodiments, the invention includes a second adjustor mounted and configured for adjusting a height of the back-up roll, and thus generally defining a limit to movement of the ultrasonic horn away from the anvil roll.
In some embodiments, the closed loop control apparatus is connected to the horn support apparatus.
In other embodiments, the closed loop control apparatus is connected to the anvil support apparatus.
In some embodiments, the anvil moving assembly defines a limit to travel of the anvil support apparatus away from the horn support apparatus, thus defining a limitation to withdrawal of the anvil roll from the nip.
In some embodiments, the invention includes first and second support rolls releasably supporting opposing sides of an outer surface of the ultrasonic horn. Axes of the first and second support rolls can be positioned lower than the axis of the ultrasonic horn, whereby urging the first and second support rolls inwardly against the outer surface of the ultrasonic horn lifts the ultrasonic horn upwardly against the back-up roll.
In some embodiments, the invention includes drawing apparatus, capable of drawing the workpiece segments through the bonding apparatus,
Chapple Scott Gerald
Couillard Jack Lee
Lohoff Michael Lee
Kimberly--Clark Worldwide, Inc.
Sells James
Wilhelm Thomas D.
Wilhelm Law Service
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