Textiles: fiber preparation – Assembling – Formed web
Reexamination Certificate
2001-12-03
2002-08-20
Worrell, Danny (Department: 3765)
Textiles: fiber preparation
Assembling
Formed web
C019S163000, C019S296000
Reexamination Certificate
active
06434795
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a method for controlling the profile of a non-woven fleece.
The present invention also concerns an installation for production of a fleece of non-woven fibres.
BACKGROUND OF THE INVENTION
It is known to produce a fibrous product, such as a fleece web, in a carding machine or other apparatus such as, for example, a pneumatic fleecing machine. The fibre web thus obtained is fed into a crosslapper in which the web is alternately folded one way and the other on a delivery belt. The fleece is thus made up of web segments inclined alternately one way and the other, which overlap. The folds between successive segments are aligned along the lateral edges of the fleece produced.
The fleece of fibres which is obtained is generally intended for subsequent consolidation processing, for example by needling, by coating and/or etc. to obtain a consolidated non-woven product.
FR-A-2 234 395 teaches the speed ratios that must be complied with in the crosslapper to control the thickness of the fleece at any point across its width.
DE-C-1 287 980 teaches placing directly at the exit of the crosslapper, above the longitudinal axis of the fleece, a gauge 32 which detects defects in thickness/surface weight of the fleece along its axis. This detection is received by a processing device which, in case of a discrepancy from a set reference, corrects in particular the speed of the delivery belt of the crosslapper when an incorrect overlapping of the web segments forming the fleece produces transverse wads or, conversely, gaps in the form of transverse grooves in the fleece. In case of a deviation of the thickness of the fleece relative to a set reference, the processing device orders a corresponding variation in the rotation speed of the doffer of the carding machine which is installed upstream of the crosslapper.
EP-A-0 315 930 proposes a crosslapper producing a fleece having, in cross-section, a non-uniform thickness/surface weight profile. To this end, the lapper carriage, which deposits the web at a variable point on the width of the delivery belt, is actuated at a speed which varies in relation to the speed of the belts which eject the web across this carriage to deposit it on the delivery belt of the crosslapper. If, at a given position on the fleece width, the carriage moves at a speed higher than that at which it feeds the fibre web, the fibre web is stretched, and this reduces the thickness of the fleece at that place. If, on the other hand, the carriage speed is below the feeding speed, the fibre web is deposited in a compressed form, which increases the thickness of the fleece at that point.
EP-B-O 371 948 describes a method intended to pre-compensate for the defects occurring during subsequent consolidation, in particular needling, by locally varying the thickness of the web introduced into the crosslapper. This is achieved by automatically controlling the speed of a doffer of the carding machine relative to the speed of the carding drum. The more quickly the doffer turns relative to the drum, the more the surface weight of the fibre web formed by the doffer is reduced.
FR-A-2 770 855 describes various improvements to this process and proposes modified embodiments combining modulation of the longitudinal profile of the fibre web produced by the carding machine or like apparatus with a stretching and/or compression action of the fibre web as it leaves the lapper carriage of the crosslapper.
A computer-controlled processing device enables the user to input a reference profile desired for the fleece and then commands the fibre web production equipment and/or the crosslapper in a manner which is calculated in view of realization of the requested profile. In practice, the user of the installation attaches decisive importance to the profile of the consolidated fleece obtained. This profile is inevitably modified by functional imperfections of the crosslapper and of the consolidation machine, notably when the latter is a needling loom. Needling looms perform the function of interlacing the fibres. At the same time they have the disadvantage of reducing the transverse dimension of the fleece and providing a fleece that is thicker along the edges than in the median zone.
The installations described in EP-B-O 371 948 and FR-A-2 770 855, as well as the crosslapper described in EP-A-0 315 930, in principle make it possible to give the fleece leaving the crosslapper a non-uniform profile which pre-compensates for the defects which will be produced by the needling loom. But in practice, perfect pre-compensation is very difficult to achieve, necessitating laborious adjustments. Moreover, it is not certain that a good initial adjustment will suffice in the long term to obtain a consolidated product in conformity with the expected ideal profile.
SUMMARY OF THE INVENTION
The object of this invention is thus to propose a method and a production installation which makes it possible for the user to obtain, more simply and more reliably, the profile desired for the consolidated fleece.
According to a first aspect of the invention, the method for controlling the transverse profile of a non-woven fleece in an installation for production of said fleece, in which, at a measuring station, a physical magnitude of the fleece is detected and on the basis of this detected value the profile of the fleece is corrected by adjusting an operation parameter of at least one fibre-arranging unit situated in the installation upstream of the measuring station, is characterized in that
at the measuring station the physical magnitude is detected at several points across the fleece width so as to record a transverse profile of the fleece;
in case of a discrepancy between the profile recorded and a reference profile, the operation parameter is corrected when said unit is working the fibres which will be located at the point on the fleece width where the profile discrepancy appeared.
“Fibre-arranging unit” is the term applied to a unit belonging, for example, to a carding machine or a crosslapper and which has an effect on the arrangement or distribution of the fibres in the fibre web or the fleece, and which has an influence in particular on the surface weight of a “fibre web cross-section” or of a point on the fleece width. “Fibre web cross-section” is the term applied to a transverse section of a fibre web or other fibrous product at a specific point along its length. This cross-section is characterised in particular by its surface weight, which can vary from one cross-section to another.
With the invention, the transverse profile obtained is continually or intermittently checked, and targeted corrections are carried out if there is a discrepancy between a point on the profile obtained and the corresponding point on the reference profile.
The correction can be carried out using a method known per se according to EP-A-O 315 930, EP-B-0 371 948 or FR-A-2 770 855.
The physical magnitude which is measured can be chosen from a wide range. For example, the permeability of the fleece to a given radiation can be measured. This permeability constitutes a physical magnitude representative of the local surface weight.
The method described in FR-A-2 770 855 requires precise knowledge of the “delay length”, i.e. the length of fibre web between a first fibre web cross-section in the process of being deposited on the fleece being formed in the crosslapper, and a second fibre web cross-section located at the point on the fibres path, where adjustment of the specific weight is carried out upstream of the crosslapper, in particular in the carding machine. If the fibre web is subjected to stretching or compression between these two cross-sections, a correspondingly corrected delay length must be taken into account. The corrected delay length corresponds to the total running length travelled by the lapper carriage above the delivery belt between the time-point when it deposits the first cross-section mentioned and the time-point when it deposits the second cross-section mentioned. By knowing this
Jean Robert
Jourde Bernard
Laune Jean-Christophe
Asselin
Young & Thompson
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