Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – Projecting particles in a moving gas stream
Reexamination Certificate
2000-10-23
2003-10-07
Theisen, Mary Lynn (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
Projecting particles in a moving gas stream
C264S517000, C264S518000, C425S080100, C425S083100
Reexamination Certificate
active
06630088
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to forming receptacles and methods for receiving particulate material thereon, and thereby fabricating particulate congregates for use as absorbent cores in personal care absorbent articles. More particularly, one of the contemplated applications for the present invention is in a forming drum comprising a plurality of forming receptacles designed and configured to form particulate congregates for use as absorbent cores in personal care absorbent articles.
Current forming media used to form particulate congregates for use as absorbent cores in personal care absorbent articles comprises a perforated plate or woven screen having a 20×20 or 30×30 thread weave per inch wherein the holes are arranged in a rectangular pattern. While the geometry of the known art is functional, such geometry does have significant drawbacks.
The holes arranged in a rectangular pattern, typical of woven screens and perforated plates used in the art, does not facilitate optimum formation of personal care absorbent articles because the fraction of the open area represented by the holes in the screen or plate, is so low as to impede desired rates of air flow through the screen or plate. There is a need for a more porous media.
The inventors herein have discovered that rectangular arrangement of the forming media holes is less efficient than improved media of the invention.
The hole size of the conventional screens is nearly twice the size of an average particle of super-absorbent material (SAM) as may typically be used in fabricating personal care absorbent articles. SAM lost by passing through the e.g. screen or perforated plate results in significant in-process loss that must be compensated for by overfeeding the SAM system.
The conventional hole arrangement is also subject to plugging, caused by a single particle, or multiple particles, of SAM getting lodged into a single perforation or hole. Compressed air is periodically used to dislodge as many of the plugged holes as possible. Over the course of a few weeks, screens become significantly plugged, the machine must be shut down, and the screens must be removed and steam cleaned, thus significantly hindering the quality and rate of operation for production of significant elements of personal care absorbent articles.
Screen plugging is also a common occurrence with woven wire screens. The weaving of the wires creates “pinch points” that trap fibers. The pinch points also become more severe as a flat screen is distorted into the three-dimensional shape of a pocketed forming surface. The pinch points tend to become an even greater problem as the what-was square or rectangular shaped openings of the screen become distorted into a rhombus or diamond-shape through the process of forming a receptacle. This distortion, or pinching off, of the holes can create a significant amount of pinch points and can be severe enough that localized areas of the screen have significantly poor porosity. Thus, different areas of the screen have different porosities, resulting in different air flow rates through the screen at the different areas. Different air flow rates define respective different levels of accumulation of absorbent core material, e.g. fiber and SAM, at the respective different areas, whereby the interval uniformity, or thickness, within a given absorbent core so produced may be less than desired.
The problem for the present invention is thus to provide forming media, as well as methods, for receiving particulate material thereon, and thereby fabricating particulate congregates for use as absorbent cores in personal care absorbent articles, whereby the holes in the forming media are not arranged in a rectangular array, and whereby the configurations of individual ones of the holes in the forming media discourage plugging of the forming media.
It is an object of this invention to create a geometric mismatch between SAM particles and respective forming media holes, by employing hole configurations which reduce the frequency of SAM particles getting lodged in the holes and thus reducing or closing off air flow through the respective holes.
It is another object of this invention to create forming media, void of pinch points and burrs which catch SAM particles and promote plugging, by employing forming media which are manufactured to be absent such pinch points and burrs.
It is yet another object of this invention to improve on the current linear arrangement of holes in forming media, by employing a hole arrangement which promotes improved airflow.
It is still another object of this invention to improve effectiveness of airflow throughout the forming area, by employing forming media having optimum porosity.
SUMMARY OF THE DISCLOSURE
In a first family of embodiments, the invention comprises a forming receptacle. The forming receptacle is adapted and configured to receive particulate material thereon, including super-absorbent particles, for thereby fabricating particulate congregates for use as absorbent cores in personal care absorbent articles. The forming receptacle comprises sheet material defining a bottom wall of the receptacle, and a side wall of the receptacle extending upwardly from the bottom wall thereby to define a particulate-receiving cavity in the receptacle. The bottom wall and the side wall have, in combination, a first major surface disposed toward the cavity, an opposing second major surface disposed away from the cavity, and a thickness between the first and second major surfaces. The forming receptacle also comprises an array of apertures extending through the bottom wall, and optionally through the side wall, and connecting the first and second major surfaces, and further comprises a matrix of the sheet material between respective ones of the apertures and defining outer perimeters of respective ones of the apertures.
In some embodiments, the bottom wall and the side wall, in conjunction, comprise a particulate receiving cavity having a depth of at least about 0.001 inch to about 2.00 inches. Yet in other embodiments, bottom wall and the side wall, in conjunction, comprise a particulate receiving cavity having a depth of about 0.00 inch.
In some embodiments, the apertures comprise aperture walls extending from the first major surface to the second major surface, the respective aperture walls tapering generally outwardly from central axes of the respective apertures, and from the first major surface toward the second major surface.
In some embodiments, the aperture walls define cross-sectional areas of such apertures along the thickness of the sheet material, including a first locus defining a smallest cross-sectional area, and a second locus defining a relatively larger cross-sectional area displaced from the smallest cross-sectional area and disposed, from the first locus, toward the second major surface of the sheet material. The smallest cross-sectional area can be displaced from and between both of the first and second surfaces.
In preferred embodiments, the apertures can define cross-sectional areas proximate the first and second surfaces, the cross-sectional area proximate the second surface being greater than the cross-sectional area proximate the first surface.
In some embodiments, the apertures comprise aperture walls extending generally perpendicular to the first surface from loci adjacent the first surface to interior loci between the first surface and the second surface, and tapering generally outwardly from the interior loci to the second major surface, whereby open areas defined by the respective apertures at the second major surface are greater than open areas defined by respective ones of such apertures at the first major surface.
In some embodiments, the aperture walls taper inwardly from the first major surface and toward the second major surface, to a throat zone, and taper outwardly from the throat zone to the second major surface, such that the throat zone defines an opening smaller in cross-section than corresponding openings defined by the respective ap
Duhm Daniel Mark
Shimon Steven John
Venturino Michael Barth
LandOfFree
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