Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-11-30
2002-09-24
Sells, James (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S290000, C156S308400, C156S553000, C156S555000, C156S580200, C156S582000
Reexamination Certificate
active
06454890
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus and methods for effecting up to full-width ultrasonic bonding on at least one continuously moving web, or work piece attached to a continuously moving web, using ultrasonic bonding apparatus. The invention more particularly concerns apparatus and methods for effecting up to full-width ultrasonic bonding on at least one continuously moving web using rotary ultrasonic bonding.
It is known to bond at least one continuously moving substrate web along up to its full width by constrictively passing the web between multiple rotating ultrasonic horns and a common, multiple repeat, full-width rotating anvil roll. Typically, the anvil roll includes one or more arrays of raised projections configured to bond the web in a predetermined bond pattern. The rotary ultrasonic horns are capable of expressing ultrasonic energy at a bonding surface to ultrasonically bond the web as the web constrictively travels between the rotary ultrasonic horns and the common anvil roll. Representative examples of rotary ultrasonic horns which have been used to bond at least one web are described in U.S. Pat. No. 5,096,532 to Neuwirth et al issued Mar. 17, 1992; and U.S. Pat. No. 5,110,403 to Ehlert issued May 5, 1992.
The consistency and quality of the bond when using such rotary bonding techniques is dependent on the consistency of the force exerted on the web by the combination of the anvil roll and the bonding roll; the time during which the web is being pressed in the constrictive nip which is dependent on, among other things, the operating speed; and the types of 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.
In the above conventional technology, to achieve full-width bonding, the web or webs being acted on are wrapped in surface-to-surface relationship with the rotary anvil over a substantial portion of the circumference of the rotary anvil. Multiple rotary ultrasonic horns used in combination with a common anvil can be acceptable for bonding thin webs along the full width, but webs with thin and thick sections such as diaper webs, which include intermittently spaced fluff pads, are not readily adapted to such wrapping of the rotary anvil. The anvil tends to need longitudinally-spaced reliefs centered on the width of the anvil to allow such fluff pads to pass through the horn/anvil nip. The only way to provide such reliefs under conventional methods is to use a bearer ring, to use a continuous bond line as a bearer, or to cam the horns in unison with the thick-to-thin section transition of the web, into and away from the anvil.
Another problem with the conventional method and apparatus is that positioning more than two horns against a single, common anvil requires the use of multi-repeat anvils. The use of multi-repeat anvils is dictated by the phenomena that only two horns can fit against an anvil at any point on its circumference. The occurrence of any run-out makes getting good bonds on more than one anvil very difficult using multi-repeat anvils.
Adjusting a single horn against a rotary anvil having a single repeat pattern can be accomplished with relative ease, but if the anvil comprises two repeats, making the horn contact both patterns with equal force is more difficult, unless run-out is generally less than 0.0002 inch TIR (Total Indicator Runout). As a result, conventional anvils are costly and not interchangeable.
As used herein, the term “runout” expresses changes in the radius of the rotary anvil roll and/or the rotary ultrasonic horn about the circumference of the respective rotary element.
Conventional methods for rotary bonding include a rotating ultrasonic horn which is mounted in a cantilevered configuration such that the horn is not supported about the surface of the bonding roll. However, such conventional methods have not always been sufficiently satisfactory.
Use of full-width bonding anvil rolls has inherent limitations which adversely affect the bond quality and which in this invention can be at least partially corrected by replacing a cantilever configuration with an in-line or balanced force application which effectively off-sets the effect of application of forces through cantilevered configurations.
In cantilevered configurations, it has been very difficult to maintain the desired degree of consistency and stability of nip force between the bonding rolls and the common anvil roll. As a result, in many conventional methods for rotary full-width bonding, bond quality and/or consistency has been undesirably variable both along the length of the bond region and across the width of the bond region. In addition, processes using cantilevered rotary ultrasonic horns have not been as robust as desired for a manufacturing environment.
When using conventional methods for full-width rotary bonding in such configuration, the bond quality has typically been less than satisfactory along the length of the bond pattern. Such inconsistency in the bond pattern has been due, at least in part, to inconsistent levels of force being effectively applied along the length of respective intermittently applied bond regions of the bond pattern. Typical of such inconsistency is excessive nip loading at such leading edge of the bond region, and insufficient nip loading behind the leading edge of the respective element as the bonding apparatus flexes or deflects in combination with development of the respective bonding region at the nip. Both the excessive nip loading and the insufficient nip loading have resulted in poor bond quality and poor bond consistency.
Under excessive loading, 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 excessive pressure to the softened materials, whereby 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.
Generating ultrasonic bonds depends on the combination of frequency and amplitude of the vibrations, the amount of pressure applied, and the time during which pressure is applied. Under conditions of insufficient loading at the nip, too little pressure is applied to the materials intended to be softened thereby, whereby the amount of energy transferred to the elements to be bonded together is insufficient to develop sufficiently strong bonds.
Conventional methods for full-width rotary bonding have used different approaches to diminish the variations in consistency of the interference. For example, the bonding rolls, anvil roll, and support frames have been precisely machined to minimize run-out in the bonding system.
The above-mentioned difficulties of maintaining desired bond quality and consistency along both the length and full-width of the web become even more acute when bonding at least one continuously moving web using multiple rotary ultrasonic horns. Operation of multiple rotary ultrasonic horns includes movement inherent in the continuous vibration of the horns at a given frequency and amplitude to efficiently bond the web, as well as rotation of the horns along the length of a web which may vary in thickness along the length of the web, thus to impose varying resistance to the nip pressure applied by the combination of each horn and the anvil on the web. Under certain conditions, such vibratory movement of the horn, and variation of web thickness, either alone or in combination, may adversely affect bond consistency and quality in the web.
In addition, where the web advancing through the nip, defined between a horn and the anvil, varies in thickness and/or density, the web can apply a correspondingly varying back pressure on the horn and anvil. The overall result of nip variation, then, can be defined in terms of the combination of the degree of variability in manufacturing and mounting the horn and anvil, as well as the degree o
Abel Kent William
Couillard Jack Lee
Nason Robin Kurt
Kimberly--Clark Worldwide, Inc.
Sells James
Wilhelm Thomas D.
Wilhelm Law Service
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