Arrangement for air-layer fibre bodies on a moving air-permeable

Details Arrangement for air-layer fibre bodies on a moving air-permeable Arrangement for air-layer fibre bodies on a moving air-permeable

1997-05-01

1999-03-23

Ryan, Patrick

Plastic article or earthenware shaping or treating: apparatus

Air felting type shaping means

Means forming stratified products

19302, 264113, 264518, D04H 172

Patent

active

058856234

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to an arrangement for fibre-laying on a moving air-permeable conveyor path fibre bodies which are comprised of at least two different layers, wherein the arrangement includes for each fibre layer air-laying units which are arranged mutually sequentially in the movement direction of the conveyor path, wherein each such unit includes means for delivering a stream of air-borne fibres to a region above the moving conveyor path, means for generating a subpressure beneath the air-permeable conveyor path in the delivery region of the stream of air-borne fibres, and means for shielding the stream of air-borne fibres from ambient air.


BACKGROUND OF THE INVENTION

Such arrangements are often used to form the absorbent bodies included in diapers, sanitary napkins, incontinence guards and like products, and the bodies often include more than one layer. One problem encountered when air-laying a fibre layer on top of an earlier laid layer is that because of the pressure difference between the interior of the mat-forming hoods which delimit the flows of air-borne fibres, air currents occur at the edges of the hoods, these air streams or air currents having a transversal direction relative to the air-borne fibres and are able to damage or destroy the earlier laid layer. EP-B1-0,292,624 teaches a solution to this problem. This prior document describes two mat-forming hoods which are mounted one immediately after the other, and two vacuum boxes which coact with the hoods. In order to avoid a difference in pressure at the join between the two hoods, the vacuum box of one hood extends beneath the other hood. One drawback with this solution is that the air-laying of fibres beneath one hood is effected under the influence of the subpressure that prevails in two different vacuum boxes, which results in inhomogeneities in the formed layer, and the stream of air-borne fibres is disturbed as a result of the pressure difference occurring in the hood. Another drawback is that the hoods are joined together via a relatively broad gap which equalizes the pressure difference between the hoods in the region of the join.
An object of the present invention is to solve the aforesaid problems in a manner which does not encumber the solution with the drawbacks of the known arrangement.


SUMMARY OF THE INVENTION

This object is achieved in accordance with the invention by means of an arrangement of the kind defined in the introduction which is characterized in that between each pair of means arranged mutually sequentially in the movement direction and delimiting a stream of air-borne fibres there is provided a transition or bridging region into which ambient air can enter freely; and in that the means which generate a subpressure beneath the air-permeable conveyor path extend beyond the fibre-stream delimiting means and into the transition or bridging region. Because the subpressure generating means extend into the transition region, there is formed a local subpressure at the limits of the transition region so that the pressure in the ambient air externally of the stream of air-borne fibres will be locally equal to the pressure in the stream, therewith eliminating the occurrence of transverse air-streams in the intermediate region between hoods and transition regions. Because the fibre layer that passes through the transition region has already been laid, no inhomogeneities will occur in the layer as a result of the influence of the different sub-pressures in the two vacuum boxes.
According to one preferred embodiment of the arrangement in which the moving conveyor path is comprised of a succession of moulds having air-permeable bottoms and disposed around the periphery of a mat-forming drum and in which at least two mat-forming hoods which each coact with an individual vacuum box are mounted peripherally one after the other and radially outside the mat-forming drum, each pair of mat-forming hoods is separated from another circumferentially, so as to provide between the hoods a transition

REFERENCES:
patent: 4904440 (1990-02-01), Angstadt
patent: 5004579 (1991-04-01), Wislinski et al.
patent: 5064484 (1991-11-01), Craig et al.

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