Textiles: manufacturing – Textile product fabrication or treatment – Fiber entangling and interlocking
Reexamination Certificate
1999-11-16
2001-12-04
Vanatta, Amy B. (Department: 3765)
Textiles: manufacturing
Textile product fabrication or treatment
Fiber entangling and interlocking
C028S106000
Reexamination Certificate
active
06324738
ABSTRACT:
BACKGROUND
0
F THE INVENTION
It is known from U.S. Pat. No. 4,701,237 to confer a perforated structure on a pre-fabricated nonwoven with the unperforated nonwoven being slit several times lengthwise, then stretched laterally to produce the holes, and fixed in this form by heat. A perforated nonwoven of this kind has sharply delimited holes but little lateral strength.
The type of manufacture according to U.S. Pat. No. 3,750,237 is better in this regard, with the prefabricated nonwoven being held between two endless webs and impacted by strong water jets to produce the perforated structure. The desired perforated structure is mounted on the endless web, such as a drum. It consists of a uniformly perforated drum covered all the way around by an endless screen. The endless screen has open and closed areas, depending on the desired hole structure. The disadvantage of this method of producing the holes lies in the fact that no holes with sharply delimited edges can be produced in this fashion and individual nonwoven fibers are pushed toward the endless screen by the strong water jets when the holes are produced and then are caught between the wires of the screen. In addition, the strength of the perforated nonwoven is low since the width of the ribs between the holes is nonuniform. A closer examination of the nonwoven structure reveals disadvantageous interference bands. These are produced by the holes in the drum that have the screen stretched over them and the fixed arrangement of the jets in nozzle beam A.
Sharply delimited holes can be produced subsequently in a prefabricated uniform nonwoven only with the type of manufacture according to EP-A-0 215 648, 0 223 614, or 0 273 454. In each case, a perforated drum is made from a smooth piece of sheet metal with drainage openings, on which drum plastic elevations are provided between the openings and are distributed uniformly over the surface. The plastic elevations can consist of beads that are open halfway, so that drainage openings are also formed at the same time, or of mandrels that taper to a tip at the top and are uniformly distributed, between which the drainage openings in the sheet are arranged in the form of holes. Although this drum can be used to produce the desired holes that are sharply delimited from the nonwoven, the strength of a nonwoven products punched to form circles is not uniform in all directions. The prescribed hole structure or the specified arrangement of plastic elevations in the form of a rhombus or the like prevents this dimensional stability. In addition, the feared interference bands can also appear on the treated nonwoven because the arrangement of the holes in the sheet metal of the drum can interfere with the necessarily permanent arrangement of the nozzle holes in the nozzle beam to form bands.
SUMMARY OF THE INVENTION
The goal of the invention is to provide a device with which all of the conditions of the type mentioned can be met. The holes in the nonwoven not only must be sharply delimited but the perforated nonwoven must possess uniform strength in all directions, not only in the width and perpendicularly thereto, assuming of course that such a uniformly solidified nonwoven was delivered before the hole structure was produced, and shows no interference bands.
Taking its departure from a device according to EP-A-0 215 684, consisting of an endless smooth surface that supports and transports the nonwoven and which is provided with drainage openings to carry away the liquid sprayed at high pressure from many jets in a nozzle beam and also with plastic elevations projecting from the smooth surface to produce the perforations in the nonwoven, the invention consists in the elevations being distributed nonuniformly over the endless surface in both dimensions and in the elevations being distributed with nonuniform spaces between them according to the random principle (use of a random generator) to cover the entire surface supporting the nonwoven. All problems are eliminated with a single stroke. Since the holes are distributed randomly and nonuniformly over the surface of the nonwoven, the highest strength of the perforated nonwoven cannot have a preferred direction. At the same time, no interference bands can any longer appear across the width of the nonwoven, since the water jets emerging from the nozzle beam always strike the elevations at different positions. Thus, the pattern of the perforated nonwoven features nonuniformly distributed holes but the holes cover the entire surface of the nonwoven uniformly and not include any uniform repeating changes such as bands.
In general, the smooth endless surface will be in the form of a drum but it is also possible to use an endless belt to produce the holes. Because of the many drainage openings distributed over the surface of the wall and located close together, because of the production of the plastic elevations as well as the holes in the wall by laser beams for example, the smooth surface in a cross section of the wall can have only a limited thickness. It Is therefore advantageous for lengthwise rails to be provided on the opposite side of the strip or inside the wall of the drum to support the band or drum wall when drawing off the sprayed liquid as required on both sides of the water jets that strike the nonwoven and hence the surface supporting the nonwoven. The suction of the pump can then act between the lengthwise supporting rails.
The plastic elevations, such as mandrels, according to requirements based on practice, should cover the area 20 to 50% and generally 30%. The open surface of the nonwoven is then correspondingly large. The drainage openings which generally consist of drilled or burned holes should then have a diameter of 0.5 to 3 mm, generally 1.5 mm. In this fashion, the sprayed liquid can be carried away faster without the fibers of the nonwoven penetrating the holes and becoming caught there.
The required diameter of the mandrels as well as the distances between them can be calculated as a function of the open area desired by the industry using the equation
O
A
=(D
ø
/D
spacing
)
2
×0.9
Here, O
A
is the open surface in the nonwoven based on the number of holes or the hole dimensions and structure in the nonwoven, D
ø
represents the effective diameter of the hole structure of the plastic elevations (mandrels) and D
spacing
represents the average spacing of the holes in the nonwoven or of the mandrels on the endless belt or drum. The drainage openings are then made in the wall around the mandrels with the drainage openings being distributed nonuniformly over the surface of the wall, but not according to the random principle like the mandrels but as a function of the locations of the mandrels.
When an endless belt is used as a supporting element for the mandrels, the perforated nonwoven is pulled off at an angle depending on the arrangement of a pull-off device and when a drum is used as a supporting element for the mandrels, the finished nonwoven is pulled off tangentially from the curvature of the drum while the mandrels continued moving in the same circumferential direction. When the nonwoven is separated from the production plane, forces appear at the mandrels that distort the shapes of the holes. To avoid this, the invention provides in one embodiment of the device that the flanks of the plastic elevations such as mandrels, at least as viewed in the transport direction of the nonwoven, that outer flank of the respective plastic elevation, has the form of an involute. Thus the perforated nonwoven separates easily from the mandrels, like gears meshing with one another.
REFERENCES:
patent: 3330009 (1967-07-01), Hynek
patent: 3617417 (1971-11-01), Olsen
patent: 3681184 (1972-08-01), Kalwaites
patent: 3837046 (1974-09-01), Kalwaites
patent: 5098764 (1992-03-01), Drelich et al.
patent: 5238644 (1993-08-01), Boulanger et al.
patent: 5274893 (1994-01-01), Kitamura et al.
patent: 5301401 (1994-04-01), Suzuki et al.
patent: 5414914 (1995-05-01), Suzuki et al.
patent: 5632072 (1997-05-01), Simon et al.
patent: 5727292
Antonelli Terry Stout & Kraus LLP
Fleissner GmbH & Co. Maschinenfabrik
Vanatta Amy B.
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