Textiles: fiber preparation – Assembling – Formed web
Reexamination Certificate
1997-12-05
2001-03-06
Worrell, Danny (Department: 3741)
Textiles: fiber preparation
Assembling
Formed web
C019S161100, C019S296000
Reexamination Certificate
active
06195844
ABSTRACT:
The present invention relates to a method of producing a textile fleece by means of a crosslapper.
The present invention also relates to various devices making it possible to use this method.
It is known to produce a lappable web in a carding machine or in another device such as, for example, a pneumatic fleecing machine. The lappable web thus obtained feeds a crosslapper in which the web is folded alternately in one direction and then in the other on an output belt. The fleece is thus composed of web segments, alternately inclined in one direction and in the other, which overlap. The folds between successive segments are aligned along the lateral edges of the fleece produced.
The fleece of fibres produced is generally intended for a subsequent process of consolidation, for example by needling, coating, and/or etc . . .
FR-A-2 234 395 reveals the speed relationships with which it is necessary to comply in the crosslapper in order to control the thickness of the fleece at all points in its width.
According to EP-A-0 315 930, the fleece can have, in cross-section, a non-uniform thickness profile. To achieve this, the speed of the lapper carriage which deposits the lappable web at a variable point in the width of the output belt is varied with respect to the speed of the belts which feed the web onto the output belt through this carriage. If, in a given position in the width of the fleece, the carriage moves at a speed greater than that at which it feeds the web, the web is stretched and this reduces the thickness of the fleece at this location. If, on the contrary, the speed of the carriage is less than the feed speed, the web is deposited in a compressed form which increases the thickness of the fleece at this location.
This method of profiling the fleece has certain limitations. With certain types of fibres or certain types of webs, in particular those in which the fibres are strictly longitudinal, the traction or compression stresses imposed on the web tend to be absorbed by elasticity after the depositing of the lappable web on the output belt, and/or to be transmitted to adjacent regions of the web. Furthermore, the traction or compression imposed on the web cannot, without risks, exceed certain limits which vary according to the nature of the web and of the fibres.
EP-B-0 371 948 describes a method intended to pre-compensate for the faults arising during the subsequent consolidation, in particular during the needling, by locally varying the thickness of the lappable web fed into the crosslapper. This is obtained by automatically regulating the speed of a doffer of the carding machine with respect to the speed of the carding machine drum. The faster the doffer rotates with respect to the drum, the lower the weight per unit area becomes. The purpose of the present invention is to improve this known method with regard to at least one of the following aspects:
inertias involved in order to vary the weight per unit area of the web entering the cross-lapper;
accuracy in so determining an elementary web cross-section in which a predetermined weight per unit area must be produced, that this cross-section will occupy a predetermined position in the width of the fleece produced by the crosslapper;
compatibility between the variable speeds of the doffer and the speeds, also variable, of the lapper carriage of the crosslapper;
broadening of the possible applications of the method;
definition of new structures for the lappable web.
According to the first aspect of the invention, the method of producing a textile fleece in which there is produced at least one elementary web and then, by means of a crosslapper, a lappable web incorporating said elementary web is folded, alternately in one direction and in the other, on a transverse output belt of the crosslapper, is characterised in that by substantially modifying at least one adjustment upstream of the crosslapper according to a periodic law, the lappable web fed into the crosslapper is given a weight per unit area which varies along the longitudinal direction of the lappable web in such a way that the fleece obtained at the output of the crosslapper has over its width a substantially predetermined distribution of weight per unit area.
It can be advantageous that the adjustment which is modified upstream of the crosslapper comprises an adjustment affecting the carding machine in a zone located downstream of a drum of the carding machine, with respect to the direction of transit of the fibres in the carding machine, and independently of the speed of rotation of a doffer taking from the carding drum the fibres intended to constitute the elementary web.
The rotational movement of the doffer involves high inertias and this limits the reaction speed when modifying the adjustment of the speed of rotation.
By making the adjustment other than by variation of the speed of rotation of the doffer, it is possible to make faster and therefore better located variations. In particular, it is possible to vary the spacing between the periphery of the drum and the periphery of the doffer. The greater this spacing becomes, the thinner the layer of fibres taken by the doffer from the drum becomes. There is also the advantage that this adjustment method does not modify the production speed of the web and therefore does not raise any particular problem at the input of the crosslapper.
The invention also contemplates varying the speed of devices placed upstream of the doffer. For example, it is possible to vary the speed of the devices called “feeder” devices of the carding machine which feed, at least indirectly, the carding machine drum with fibres upstream of the said drum. It is also possible to vary the speed of the carding machine drum with respect to the doffer. All of these solutions also have the advantage of not affecting the production speed of the web which can therefore remain at each instant equal to a constant speed of input into the crosslapper. In order to reduce the inertia of the drum, the latter can be made from carbon.
When the doffer is followed by at least one condenser cylinder, it is possible to vary the speed of at least one condenser cylinder with respect to the doffer in such as way as to more or less condense the elementary web taken from the drum by the doffer.
The last element at the output of the carding machine generally consists of a device called a detacher which detaches the web from the last condenser cylinder, or from the doffer in the absence of a condenser cylinder. It is also proposed, according to the invention, to regulate the weight per unit area of the web by varying the action of the detacher. In particular, when this detacher is a rotating cylinder provided with a peripheral lining, it is possible to vary the speed of rotation of the detacher with respect to the rotary device, for example a doffer or a condenser, located immediately upstream.
According to an important aspect of the invention, when the adjustment made has the effect of varying the speed at which the web produced is supplied to the crosslapper, which is particularly the case when the procedure is to vary the speed of a doffer, a condenser cylinder or a detacher, the speed of input into the crosslapper is caused to vary in such a way that it substantially corresponds, at each instant, to the speed at which the web arrives at the crosslapper, and at each instant the length of a web accumulation path in the crosslapper is adjusted in order to compensate for the differences between the instantaneous speed of input into the crosslapper and the instantaneous speed at which the crosslapper feeds the lappable web onto the output belt.
The known crosslappers define a web accumulation path. FR-A-2 234 395 reveals a variation in the length of this path so that the speed at which the lapper carriage feeds the web onto the output belt varies and in particular is cancelled out when the speed of the lapper carriage is itself zero at its motion reversal points. According to the present aspect of the invention, the length of web accumulated in the crosslapper is a
Jean Robert
Jourde Bernard
Laune Jean-Christophe
Asselin
Greer Burns & Crain Ltd.
Welch Gary L.
Worrell Danny
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