Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – Presses or press platen structures – per se
Reexamination Certificate
2000-11-30
2003-02-11
Sells, James (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
Presses or press platen structures, per se
C156S553000, C156S555000, C156S582000
Reexamination Certificate
active
06517671
ABSTRACT:
BACKGROUND
The present invention relates to apparatus and methods for effecting ultrasonic bonding on at least one continuously moving web or work piece. The invention more particularly concerns apparatus and methods for ultrasonically bonding at least one continuously moving web using a rotary anvil roll in combination with a rotary ultrasonic horn.
It is known to bond at least one continuously moving substrate web by constrictively passing the web through a nip defined between a rotating ultrasonic horn and a 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 horn is capable of expressing ultrasonic energy at a bonding surface so as to ultrasonically bond the web as the web travels through the nip.
The consistency and quality of the bond when using such rotary bonding techniques is dependent on, among other parameters, the consistency of the force exerted on the web by the combination of the anvil roll and the ultrasonic horn; the time during which the web is under compression in the nip; the size, shape, depth, and percent bond area of a bond pattern, where the area of the bond projections as a percentage of the total surface area of the bonded region defines the percent bond area; and the properties of material or 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 has been particularly variable where the desired bond pattern is intermittent, especially where the force expressed at the nip changes significantly, and may drop to substantially zero, in concert with the intermittent nature of the intermittency of the bonding operation.
When using conventional methods for rotary bonding in such configuration, the bond quality has typically been less than satisfactory along the length of the bond pattern. According to the invention, such inconsistency in the bond pattern has been due, at least in part, to inconsistent levels of force being effectively applied along the lengths of the respective intermittent bond regions of the bond pattern. Typical of such inconsistency is relatively greater nip loading at the leading edge of the bond region, and relatively lesser nip loading behind the leading edge of the respective element as the bonding apparatus flexes or deflects in combination with the passing of the respective bonding region, typically a raised bonding element, through the nip. Both the relatively greater nip loading and the relatively lesser nip loading comprise undesired inefficiency of control of nip pressure at the respective loci, and can result in poor bond quality and poor bond consistency.
Under excessive loading, which may be encountered at the relatively greater loading levels, 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 the bonds after cooling 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 result in increased rates of wear on the ultrasonic horn and/or anvil roll, or can damage the horn and/or anvil. Finally, ultrasonic horns are generally driven by piezoelectric crystals that convert electrical energy at high frequency into mechanical vibrations. When an excessive impulse load is applied to the horn, the mechanical process works in reverse to cause a resulting electrical spike which can overload and shut down the electrical frequency generator.
Generating ultrasonic bonds depends on the combination of frequency and amplitude of the vibrations, the amount of pressure applied at the nip, and the time during which pressure is applied. Under conditions of insufficient loading at the nip, too little pressure is applied to the materials to be softened thereby, whereby the amount of energy transferred to the elements to be bonded together is insufficient to develop sufficiently strong bonds.
The above-mentioned difficulties of maintaining desired bond quality and consistency along both the length and width of the web become even more acute when intermittently bonding at least one continuously moving web using a rotary ultrasonic horn. Operation of a rotary ultrasonic horn includes movement inherent in the continuous vibration of the horn at a given frequency and amplitude to efficiently bond the web, as well as rotation of the horn as the web passes between the horn and the anvil at the nip. The web may vary in thickness along the length of the web, thus to impose varying resistance to the nip pressure being applied by the combination of the horn and the anvil on the web. Under certain conditions, such vibratory motion of the horn, and variation of web thickness, either alone or in combination, may adversely affect bond consistency and quality in the web if suitable steps are not taken to account for such thickness variation.
In addition, where the web advancing through the nip, defined between the horn and the anvil, varies in thickness and/or density, the web may apply a correspondingly varying back pressure on the horn and anvil. Thus, the overall result of variation in nip pressure, can be defined in terms of, among other parameters, the combination of the degree of variability in manufacturing and mounting the horn and anvil, as well as the degree of variability in thickness of the web moving through the nip between the anvil and horn.
These difficulties are even further exacerbated when the rotary ultrasonic bonding includes an intermittent bond pattern as discussed above such that a discrete raised array of bonding projections is introduced into the nip at the initiation of bonding of each bond region.
It is an object of this invention to provide bonding apparatus and methods wherein nip pressure is more uniform along the lengths and widths of respective bonding regions.
It is a further object to provide a transition gradient on a respective anvil roll being shaped to facilitate vertical acceleration and vertical deceleration of a complimentary ultrasonic horn.
It is yet a further object to provide a loading surface on an anvil roll, which is shaped to preclude effective bonding interference between the anvil roll and a cooperating rotary ultrasonic horn.
SUMMARY
In a first family of embodiments, the invention comprehends a ramped anvil roll for cooperating with an ultrasonic horn and thereby creating ultrasonic bonds in a work piece passing between the anvil roll and a respective such ultrasonic horn. The ramped anvil roll has first and second sides of the anvil roll defining an anvil roll width therebetween, and the anvil roll further comprises a circumference thereabout. A relatively smaller radius portion of the anvil roll extends about a first portion of the circumference, and a relatively larger-radius raised bonding element extends about a second portion of the circumference. The raised bonding element has a front end portion, a rear end portion, a width defined by first and second sides thereof, and a raised operating surface defined between the first and second sides of the raised bonding element, and between the front end portion and the rear end portion. An outer surface at at least one of the front end portion and the rear end portion of the raised bonding element defines a transition gradient between the raised operating surface and the relatively smaller radius portion of the anvil roll. The transition gradient defines a modified sinusoidally-shaped curved loading surface including an inflection locus, the curved loading surface representing a relatively constantly changing angle as measured against respective radii of the anvil roll in combination with adva
Abel Kent William
Coenen Joseph Daniel
Couillard Jack Lee
Kimberly--Clark Worldwide, Inc.
Sells James
Wilhelm Thomas D.
Wilhelm Law Service
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