Web stretching device disposed between a carding device and a cross-lapper

Abstract

Apparatus for forming a fibre mat including a fibre web-forming device (card), a cross-lapper and a device for drafting the fibre web(s) disposed between the web forming device and cross-lapper to draft the fibre web(s), in particular in a time-varying, specifically periodic manner, to adjust a predetermined desired profile of the fibre mat leaving the cross-lapper, the web-forming device including at least one output belt for at least one web, and preferably two output belts for two webs, an upper and lower web respectively; wherein the cross-lapper has an input belt receiving the web(s) from the output belt(s) of the web forming device, characterised in that the path of the at least one web, and preferably of the two, upper and lower, webs, between the output belt(s) of the web-forming device, in particular the card, and the input belt of the cross-lapper includes at least one bending point.

1 . An apparatus for forming a fiber mat, in particular a non-woven mat, comprising:
 a fiber web-forming device, for example a card, for forming at least one fiber web;   a cross-lapper supplied in the at least one fiber web to produce lapping by a to-and-fro movement of a fibre lapper carriage with a view to obtaining said fibre mat consisting of a stack of sections of the at least one fibre web transverse to each other; and   a drafting device, located between the fiber web-forming device and the cross-lapper, configured for drafting said at least one fiber web to control a pre-determined profile of the fibre mat outputted from said cross-lapper;   wherein said drafting device comprises a drive component for driving said at least one fiber web, said drive component comprising a driving surface intended to come into contact with said at least one web so as to drive it, and wherein a suction device is provided to produce suction at the driving surface to hold said at least one web against the driving surface by suction.   
     
     
         2 . The apparatus of  claim 1 , wherein the arrangement is such that the path of the at least one fiber web, preferably an upper and a lower fiber web, between the web-forming device and the cross-lapper, includes at least one inflexion point. 
     
     
         3 . The apparatus of  claim 1 , wherein the drive component is a drafting roller, part of whose outer surface constitutes the driving surface transporting the web or webs between said fiber web forming device and said crosslapper, said roller being controlled by a rotary drive mechanism whose speed of rotation varies as a function of the drafting that it is desired to impart to the at least one fiber web. 
     
     
         4 . The apparatus of  claim 3 , wherein the drafting roller is covered with a sleeve in a material providing improved adhesion to the web(s). 
     
     
         5 . The apparatus of  claim 3 , wherein the web-forming device comprises two output belts, upper and lower respectively, outputting two upper and lower fiber webs coming together at the drive component. 
     
     
         6 . The apparatus of  claim 5 , wherein the drafting roller is positioned downstream of a guide roller for each output belt to limit the distance over which the drafting force between the guide roller of the respective belt and the drafting roller is applied. 
     
     
         7 . The apparatus of  claim 5 , wherein the drafting roller is disposed at a distance from the guide roller of each belt of between 50 mm and 300 mm. 
     
     
         8 . The apparatus of  claim 5 , wherein the space between the upper output belt guide roller of the web-forming device and the drafting roller is between 5 and 20 mm, for a web area density of between 10 and 50 g/m 2 , and preferably between 20 and 40 g/m. 
     
     
         9 . The apparatus of  claim 5 , wherein the space between the lower output belt guide roller of the web-forming device and the drafting roller is between 10 and 30 mm, for a web area density of between 10 and 50 g/m 2 , and preferably between 20 and 40 g/m 2 . 
     
     
         10 . The apparatus of  claim 1 , wherein the suction device is arranged so that the thickness of the web(s) passing over the drive surface is not less than 50% of the thickness of the web directly upstream of the drive component and preferably not less than 75% of its/their thickness directly upstream of the drive component, preferably not less than 90%, and more preferably substantially equal to its thickness directly upstream of the drive component and even more preferably substantially equal to its/their thickness directly upstream of the drive component. 
     
     
         11 . The apparatus of  claim 1 , wherein the suction device is arranged to create, for a total area density of the web or webs of between 20 and 100 g/m 2 , and in particular between 30 and 80 g/m 2 , a negative pressure of between 10 millibars and 100 millibars, and in particular between 40 and 70 millibars. 
     
     
         12 . The apparatus of  claim 1 , wherein the web-forming device comprises two output belts, upper and lower respectively, outputting two upper and lower fiber webs coming together at the drive component. 
     
     
         13 . The apparatus of  claim 1 , wherein the linear peripheral, or tangential, speed of the drive component varies over a speed range of between 100 and 150% of the speed of an output belt or output belts of the web forming device, and preferably between 100 and 140%. 
     
     
         14 . The apparatus of  claim 1 , wherein the speed of an input belt of said cross lapper is substantially equal or equal to the peripheral speed of the drive component. 
     
     
         15 . The apparatus of  claim 10 , wherein the cross-lapper input belt drives the web at a speed slightly higher than that of the drive component, for example 1 to 10% greater, the drafting preferably being constant and thus independent of the variable drafting applied by the drive component. 
     
     
         16 . A method for producing a fibre mat with an apparatus comprising a web-forming device and a cross-lapper, in which:
 at least one fibre web is routed between the output of the web-forming device and the cross-lapper by passing it over a drive surface, in particular the surface of a roller,   the at least one web is held against the drive surface by suction; and   the web held against the surface is stretched.