Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
1997-12-11
2001-10-23
Aftergut, Jeff H. (Department: 1733)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C156S209000, C156S210000, C156S290000, C156S291000, C156S292000, C428S166000, C428S172000, C428S179000, C428S198000
Reexamination Certificate
active
06306482
ABSTRACT:
The present invention concerns a manufacturing method for an absorbent structure or web of at least two plies each constituted of at least one creped absorbent sheet of embossed paper.
In particular, the invention relates to making fiber products in the form of absorbent papers for household and sanitary uses.
Accordingly, the invention more specifically concerns an absorbent structure having several plies, which is also called a multi-layer structure, for products such as toilet paper, handkerchiefs, napkins, or paper towels.
The sanitary and household paper industry manufactures a variety of different products using a lightweight creped absorbent paper such as cellulose wadding or tissue paper. The stretching properties of this paper made possible by its creping is used to emboss it.
Embossing imparts bulk to the web and improves liquid absorption, touch and softness. Attempts have been made already to improve absorptivity further by creating multi-layer structures by combining at least two layers, also called plies, each constituted by at least one embossed creped absorbent paper sheet.
French Patent No. 93 00366 already proposes a method for making an absorbent structure having at least two plies, namely
a method wherein the plies are engaged between two engraved metal cylinders fitted with protrusions and driven in synchronized rotation and mutually nesting with play between the tops of the protrusions of one metal cylinder and the opposite trough surface of the engraving of the other cylinder,
a method wherein, prior to its engagement between the two engraved cylinders, each ply is shaped to follow the surface of its associated engraved cylinder by forcing the ply against the cylinder by means of an associated compression cylinder fitted with a flexible cladding, in particular an elastomer or rubber cladding,
a method wherein an adhesive is applied to the salient zones of at least one ply before the plies are engaged between the engraved cylinders.
In the method described in the document, the magnitude of the play J is selected to be no more than the thickness of the web being embossed in order to ensure calendering the web near the tops of the bosses implemented when combining the plies in the zone. However, the method entails the drawback of requiring cylinders with very tight engraving tolerances, raising complexity on an industrial scale.
Moreover, a “nested” method is known in the prior art whereby the two cylinders are sufficiently apart from each other so that, after embossing, one of the plies is detached from the cylinder and is applied against the second engraving cylinder bearing the second ply in such a manner that the protrusions of the first ply shall nest between the protrusions of the second ply. A rubber-clad laminator roll presses the first against the second ply in a manner to ensure contact between the adhesive-endowed tops of the second and first plies and their combination. This technique is shown in U.S. Pat. No. 3,867,225.
Applicant, however, observed that at very high embossing pressures, sometimes such a method results in fluttering of the ply detached off its metal embossing cylinder in the zone upstream of the laminator roll and the associated metal engraved cylinder when the ply passes through the zone in the direction of the laminator roll.
This fluttering results in forming a loop entailing an offset between the two plies and hence manufacturing defects because of the lack of registry of the two plies when they are bonded together by the laminator roll.
Besides the difficulty in maintaining synchronized displacement of the two plies before they are adhesively combined by the laminator roll, this technique furthermore incurs the drawback of requiring adequate compression of the laminator roll and one of the two engraved cylinders to achieve good adhesive bonding of the previously two plies.
On account of the resiliency of the laminator roll, the application of a comparatively large compression will entail additional or new embossing of the outer ply relative to the engraved cylinder associated with the laminator roll, whereby product aesthetics as well as softness of touch will be degraded.
The object of the present invention is to create a method combining the advantages of the two above-mentioned methods while nevertheless remedying the already described drawbacks.
For that purpose, the invention proposes a method wherein the engraved cylinders are apart by a play J measured between the tops of one cylinder and the engraved trough surface of the other cylinder and are characterized in that the play J is larger than the sum of the thicknesses of the previously shaped plies in such a manner that the plies are not compressed when being engaged between the nested engraved cylinders and in that the play J is less than the engraved depth of the cylinders.
Also the invention proposes apparatus with which to implement the method of the invention, the apparatus comprising two engraved metal cylinders fitted with protrusions and driven into synchronized rotation and mutually nesting with a play J between the tops of the protrusions of one metal cylinder and the opposite trough surface of the engraving of the other cylinder, the previously embossed plies being engaged between the cylinders, the apparatus being characterized in that the play J is larger than the sum of the thicknesses of the previously embossed plies.
Moreover, the invention proposes an absorbent structure of at least two absorbent plies made in the manner of the invention and characterized in that it evinces absorptivity measured under the AFNOR NFQ 03068 Standard exceeding 10 cm
3
/g, in particular between 11 and 14 cm
3
/g, when it is made from two sheets of creped absorbent paper each with an absorptivity between 4 and 6 cm
3
/g.
REFERENCES:
patent: 3708366 (1973-01-01), Donnelly
patent: 3867225 (1975-02-01), Nystrand
patent: 4093765 (1978-06-01), Schmidt
patent: 4483728 (1984-11-01), Bauernfeind
patent: 4543142 (1985-09-01), Kuepper et al.
patent: 5693406 (1997-12-01), Wegele et al.
patent: 5830558 (1998-11-01), Barnholtz
patent: WO 94 15776 (1994-07-01), None
Hungler Joel
Laurent Pierre
Ruppel Remy
Aftergut Jeff H.
Breiner & Breiner L.L.C.
Georgia-Pacific France
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