EP1268896A2

EP1268896A2 - Method for controlling the profile of a non-woven lap and related production installation

Info

Publication number: EP1268896A2
Application number: EP00938879A
Authority: EP
Inventors: Bernard Jourde; Robert Jean; Jean-Christophe Laune
Original assignee: Asselin SA; Asselin Thibeau SAS
Current assignee: Andritz Asselin Thibeau SAS
Priority date: 1999-06-01
Filing date: 2000-05-31
Publication date: 2003-01-02
Anticipated expiration: 2020-05-31
Also published as: ATE387523T1; WO2000073547A8; CA2375492C; CN1371435A; FR2794475B1; DE60038187D1; DE60038187T2; JP2003519291A; EP1268896B1; CN100390338C; WO2000073547A3; CA2375492A1; JP4588948B2; FR2794475A1; KR20020082399A; WO2000073547A2; US6434795B1; ES2301485T3

Abstract

An installation includes a carding machine (1), and a distributor-layer (2) depositing the card (1) web (6) in a reciprocating motion on a delivery belt (8) moving transversely. The resulting intermediate lap (16) is conveyed to a needling loom (3) to produce a consolidated lap (24). A measuring station (28) scans the consolidated lap (24) profile and transmits it to a processing unit (32) where the profile is compared to a set reference input by a terminal (33). The variations in width cause a corresponding modification in the width deposited by the distributor-layer (2) by a link (36). The local surface weight variations cause a corresponding modification of the controls applied to the carding machine (1) capable of longitudinally profiling the web (6). The invention is useful for controlling an installation for obtaining a finished product.

Description

"Method for regulating the profile of a nonwoven web and production plant relating thereto."

The present invention relates to a method for regulating the profile of a nonwoven web.

The present invention also relates to an installation for producing a sheet of nonwoven fibers.

It is known to produce a fibreu-x product, such as a covering veil, in a carding machine or in another device such as, for example, a pneumatic lapper. The veil of fibers thus obtained feeds a spreader-lapper in which the veil is folded alternately in one direction and in the other on an output belt. The tablecloth is thus made up of overlapping segments of sail, tilted alternately in one direction and the other. The folds between successive segments are aligned along the lateral edges of the sheet produced.

The sheet of fibers obtained is generally intended for a subsequent consolidation treatment, for example by needling, by coating, and / or etc., in order to obtain a consolidated nonwoven product.

FR-A-2 234 395 teaches the speed relationships which must be observed in the spreader-lapper to control the thickness of the sheet at any point of its width.

DE-C-1 287 980 teaches placing directly at the outlet of the spreader-lapper, above the longitudinal axis of the tablecloth, a gauge 32 which detects the thickness / surface weight defects of the tablecloth along its axis. This detection is received by a processing device which, in the event of deviation from a setpoint, in particular corrects the speed of the exit belt of the spreader-lapper when an incorrect overlapping of the segments of the web making up the layer produces transverse beads or, on the contrary, gaps in the form of a transverse groove in the sheet. In the event of deviation of the thickness of the sheet with respect to a setpoint, the processing device controls a corresponding variation in the speed of rotation of the card doffer mounted upstream of the spreader-lapper.

EP-A-0 315 930 proposes a spreader-lapper producing a ply having in cross section a non-uniform thickness / surface weight profile. For this, the lapping carriage, which deposits the veil at a variable point of the width of the exit conveyor, is actuated with a speed which varies relative to at the speed of the belts which expel the veil through this carriage to deposit it on the exit belt of the spreader. If in a given position of the width of the web, the carriage moves at a speed greater than that at which it unwinds the web, the web is stretched and this reduces the thickness of the web at this location. If on the contrary the speed of the carriage is lower than the speed of unwinding, the web is deposited in a compressed form which increases the thickness of the sheet at this location. EP-B-0 371 948 describes a process intended to pre-compensate the defects occurring during the subsequent consolidation, in particular the needling, by locally varying the thickness of the covering veil introduced into the spreader-lapper. This is obtained by automatically regulating the speed of a card doffer relative to the speed of the card drum. The faster the drier turns relative to the drum, the more the veil formed by the drier has a reduced surface weight.

FR-A-2 770 855 describes various improvements to this process and proposes, as a variant, embodiments combining a modulation of the longitudinal profile of the web produced by the card or the like with an action of stretching and / or compression of the web. its output from the lapping carriage of the spreader-lapper. A computer processing device allows the user to enter a desired target profile for the web and then controls the web production device and / or the spreader-lapper in a calculated manner to achieve the requested profile. In practice, the user of the installation attaches decisive importance to the profile of the consolidated sheet obtained. However, this profile is inevitably modified by the functional imperfections of the spreader and of the consolidation machine, in particular when the latter is a needling machine The needling machines have the function of interleaving the fibers They have at the same time the disadvantage of reducing the transverse dimension of the web, and to provide a thicker web along the edges than in the middle area.

The installations described in EP-B-0 371 948 and FR-A-2 770 855, as well as the spreader-lapper described in EP-A-0 315 93C, in principle make it possible to add to the outgoing sheet αe the spreader a non-uniform profile which pre-compensates defects which will be produced by the needling machine. But in practice, perfect precompensation is very difficult to obtain, requires laborious adjustments. In addition, it is not certain that a good initial adjustment is sufficient to obtain a lasting product that conforms to the expected ideal profile.

The object of the invention is thus to propose a production process and installation which make it possible to obtain, in a simpler and more reliable manner for the user, the desired profile for the consolidated sheet.

According to a first aspect of the invention, the method for regulating the transverse profile of a nonwoven web in a production facility for said web, in which, at a measurement station, a physical quantity of the web is detected and depending on the detection, the profile of the sheet is corrected by adjusting an operating parameter of at least one fiber arrangement member located in the installation upstream of the measurement station, is characterized in that

- at the measuring station, the physical quantity is detected at several points of the width of the sheet so as to raise a transverse profile of the sheet;

- In the event of a deviation between the raised profile and a set profile, the operating parameter is corrected when said member works the fibers which will be at the point of the width of the sheet where the profile deviation has appeared.

The term "fiber arrangement member" means a member belonging for example to a carding machine or a spreader-lapper and which has an effect on the arrangement or distribution of the fibers in the veil or the tablecloth, and which in particular influences the areal weight of a "sail section" or a point the width of the web. The term “sail section” is used to designate a cross section of a sail or other fibrous product at a determined point along its length. This section is characterized in particular by its surface weight, which can vary from one section to another

With the invention, the transverse profile obtained is checked continuously or intermittently and targeted corrections are made in the event of a deviation between a point of the profile obtained and the corresponding point of the setpoint profile. The correction can be made by a method known in n / a from EP-A-0 315 93C, EP-B-0 371 948 or FR-A-2 77C 855. The physical quantity measured can be chosen from a wide range. It is for example possible to measure the permeability of the sheet at a given radiation. This permeability constitutes a physical quantity representative of the local surface weight. The method described in FR-A-2 770 855 requires to know with precision the "delay length", that is to say the length of sail comprised between on the one hand a first section of sail being deposited on the web being formed in one spreader-lapper, and on the other hand a second section of web located at the point of the path of the fibers where the specific weight adjustment takes place upstream of

1 spreader-lapper, in particular in the card. If stretching or compression is experienced by the web between these two sections, a correspondingly corrected delay length must be taken into account. The corrected delay length corresponds to the total distance covered by the lapping carriage over the exit conveyor. between the time he files the first cited section and the time he files the second cited section. Knowing this delay length, possibly corrected, we know the point where will be deposited, in the width of the web, a section of sail in tram to undergo a thickness / surface weight correction in the card.

The delay length, possibly corrected, can be theoretically determined at any time in a given production installation, programmed in a given way. In practice, such a theoretical determination can be difficult to implement and not lead to a perfect result. It is in particular difficult to take into account certain elements such as the elasticity of the fibers, which are liable to stretch or, on the contrary, to recompress at certain points in their path.

According to one aspect of the invention which can, independently of the profiling regulation, usefully supplement FR-A-2 770 855, an experimental determination of the delay length is carried out or at least an experimental completion of the theoretical determination To do this, an initialization step is implemented using a specific feature of the fibrous product, the longitudinal position of which is identified along the fine product during the passage through said fiber arrangement member and then the transverse position. in the tablecloth produced Thanks to this knowledge The more precise the delay length, the profiling control method according to the invention can be implemented more efficiently.

It is advantageous that this feature is a pseudo-defect generated by the arrangement member. It is also advantageous for the characteristic, in particular the pseudo-defect, to be detected by the means for detecting the physical quantity. In this the initialization process is even more advantageously combined with the profile regulation process proper.

Knowing the length of veil necessary to feed the lapper carriage during a return trip thereof, we can deduce all the successive sail sections which will correspond to the same transverse position on the lap. And we can deduce the position of the sail sections corresponding to any other transverse position on the web.

In practice, at the same time that the passage of the particularity is identified through the arrangement member, one can identify the position of the lapping carriage in its round trip cycle. It will then be known, each time the lapping carriage returns to this position of its cycle, that the section of web being worked by the arrangement member is intended to be in the aforementioned transverse position of the web.

In an improved version, the initialization can advantageously include a step consisting of phase shifting the successive features with respect to the round-trip cycles of the lapping carriage, until the successive features are positioned in a particular position of the width of the sheet, and in particular on the central axis of the sheet.

We have thus determined the sections of the web that will be on the central axis of the web. By a simple subdivision of the length of the web between two such successive sections, we find the sail sections which will be positioned at other points of the width of the web. This subdivision can be made voluntarily irregularly to take account for example of a non-constant stretching / compression at the exit of the lapping carriage. Once the initialization has been carried out, we move on to the production stage and there is no longer -ioesom of providing the web with "particularities" or "pseudo-defects" When a correction of the transverse profile of the web is to be carried out, this correction is carried out on the sail, in a sail section chosen with reference to the sail sections which are known to lie along the axis of the web

The correction can also be carried out by modifying the speed relationship between the lapping carriage (thus becoming the fiber arrangement member used to apply the correction) and the speed of movement of the web through the lapping carriage when the lapping carriage found above the point of the width of the web where the profile deviation was found This method has the advantage of not requiring any marking between the longitudinal positions of the web and the transverse positions on the web, but may have the drawbacks mentioned in FR-A-2 770 855 with regard to EP-A-0

315 930, in particular a relatively low correction efficiency when using relatively elastic fibers.

It is therefore preferred according to the invention to make the area weight corrections during the production of the web upstream of the spreader-lapper. On the other hand, it is advantageous to correct the width of the sheet obtained, when it deviates from the width of the set profile, by adjusting the travel ends of the lapping carriage of the spreader-lapper.

In this case also, the lapping carriage is a member for arranging the fibers on which it is possible to act to apply a profile correction in the context of the regulation process.

The corrections made can have the effect of modifying the position of the lapping carriage for which the section of sail passing through the arrangement member is that intended to be placed on the axis of the tablecloth. We can then recalculate said position of the covering carriage by applying to the previously known position a variation calculated theoretically from the foreseeable effects of the correction

According to another aspect of the invention, the installation for producing a sheet of non-woven fibers, comprising fiber arrangement members, detection means for measuring a physical quantity having a traveling sheet at a measurement and control means receiving a supplied signal by the detection means and delivering to at least one of the arrangement members a modified control signal in the event of a difference between the physical quantity read and a set value, is characterized in that - - the detection means are designed to measure the physical quantity at different points of the width of the sheet;

the control means compare the physical magnitude of each point with a setpoint relating to this point, and in the event of deviation at a point apply a corrected command when the arrangement member works with fibers intended to be at said point .

Other features and advantages of the invention will emerge from the description below, relating to non-limiting examples.

In the accompanying drawings:

- Figure 1 is a plan view of an installation according to the invention;

- Figures 2, 3 and 4 are sectional views along II-II, III-III, and respectively IV-IV of Figure 1, showing the product at different stages of its development;

- Figure 5 is a schematic view along V-V of Figure 1;

- Figure 6 is a schematic view of the web deposited during a movement cycle of the lapping carriage, with the rule of correspondence between the web sections E ₂ to E ₁₇ and the measurement points P _x to P ₁₉ ;

- Figure 7 is an example of setpoint profile; FIG. 8 shows the corresponding intermediate ply, in cross section;

- Figure 9 shows the corresponding veil to produce to obtain this profile, in longitudinal section;

FIG. 10 is an example of a flow diagram for implementing the method; FIGS. 11 and 12 are similar to FIGS. 7 and 8 but relating to another example of profile,

- Figure 13 corresponds to a part of Figure 1 but at the end of the initialization step, Figure 14 is a sectional view of the consolidated sheet according to XIV-XIV of Figure 13; and

- Figure 15 is a schematic view of another embodiment of the invention It is specified here ±. that the figures are purely illustrative and do not purport to show either the details of construction or the actual proportions of the installation or of its components. In the example represented in FIGS. 1 and 5, the installation comprises a card 1, a spreader-lapper. 2 and a needling machine 3 The card 1 delivers on a transfer mat 4 a veil of fibers 6 generally oriented longitudinally with respect to the direction 7 of the transfer. The function of the spreader 2 is to receive the veil 6 in the direction 7 and to deposit it in a zigzag pattern on an output mat 8 moving perpendicular to the direction 7 The spreader-lapper comprises a lapping carriage 9 (Figure 5) which moves back and forth over the output belt 8 parallel to the width thereof The lapping carriage 9 has above the output belt 8 a slot 11 through which the web 6 is expelled at a determined speed and is deposited at a variable point of the width of the output conveyor 8. In the example shown, the slot 11 is defined between two rollers 12 whose axes are located in the same horizontal plane. spreader-lapper also comprises an accumulator carriage 13 movable back and forth above the lapper carriage 9 and parallel to it The role of the accumulator carriage 13 is to make the web 6 perform a loop 14 of variable length allowing the veil to be expelled by the lapping carriage 11 at a speed which can be chosen freely and in particular independently of the speed of reciprocating movement of the lapping carriage 9 and the speed at which the veil 6 arrives from the card 1 However, the average speed at which the web 6 arrives from the card and the average speed at which the web 6 is expelled by the lapping carriage 9 are equal over a round trip cycle of the lapping carriage

In FIG. 5, we have refrained from representing numerous details of the spreader-lapper 2 and in particular the frame supporting and guiding the carriages 9 and 13, the motors for their drive, as well as various belts supporting the web up to 'at its exit through the slot 11 of the lapping carriage 9. Such elements are described in detail for example in EP 0 517 563

Examining it simultaneously in Figures 1 and Ξ allows us to understand that depending on the speed at which the winding is going to back and forth from the lapper carriage 9, the width of the veil 6, and the speed of advance of the output mat 8, we will find at each point of the length of the mat 16 formed on the output mat 8, a number S overlapping sail segments, corresponding to S / 2 back and forth of the lapper carriage 9.

In FIG. 5, card 1 is only shown partially and very schematically Card 1 comprises a card drum 17 rotating in service in the direction indicated by an arrow 18 and carrying at its periphery a layer of fibers 19 which is constantly renewed by means not shown Part of the layer 19 is removed by a comber 21 which forms, with the fibers removed, directly or indirectly, the veil 6 As explained in detail in FR-A-2

770 855, the thickness of the web 6 can be varied by varying the speed of rotation of the drum 17 or the doffer 21, or even by varying the spacing between the drum 17 and the doffer 21. FIG. 5 illustrates more particularly the production of a sheet having at the outlet of the spreader-lapper a profile with edges progressively thinned by means of a veil 6 which, instead of having a uniform thickness, has zones

Zl and Z2 in which the surface weight of the web

(represented by the thickness in FIG. 5) decreases to a section of sail 22 then increases again. These areas

Zl and Z2 are positioned along the length of the web 6 so that the lapping carriage 9 comes to place them along the left edge and respectively of the right edge of the web 16. The section 22 of minimum surface weight coincides with the corresponding edge tablecloth 16.

The needling machine 3, mounted downstream of the spreader-lapper 2 and in particular of its outlet conveyor 8 relative to the direction of circulation 23 thereof, transforms the intermediate ply 16 made up of superimposed veil segments 6 into a ply consolidated 24 is much more compact, therefore much less thick. The width 26 of the consolidated sheet 24 is slightly reduced compared to the width 27 of the intermediate sheet 16 The consolidated sheet 24 is then transported to, for example, a storage.

According to the invention, the consolidated sheet 24 passes through a measuring station 28 located downstream of the needling machine 3 relative to the direction of travel 29 αe the consolidated sheet.

Not shown in detail, the αe measurement station 28 is equipped with a means for detecting a physical size in several points of the width αe of the consolidated sheet 24 II can be a series of individual detectors aligned along the width of the consolidated sheet 24 II can also be a single detector periodically carrying out a transverse stroke above or below the consolidated sheet 24 to capture the transverse profile of the sheet as regards the physical quantity to which the detector is sensitive. The physical quantity in question is preferably but not limited to, the permeability of the consolidated sheet 24 to radiation which may be light radiation, X-ray radiation, γ radiation, etc. This permeability is in fact relatively easy to measure with precision and gives a faithful image of the surface weight of the sheet at each measurement point. If necessary, a correspondence factor between the permeability and the surface weight can be used depending on the type of fibers or a mixture of fibers making up the sheet. Such measuring stations, comprising a row of detectors, or a single detector movable along a measurement run (the latter being commonly called "traveling") are commercially available and will therefore not be described further.

The measurement station 28 provides a measurement signal in analog or digital form which is sent by a line 31 to a processing unit 32. A terminal 33, also connected to the unit 32 allows the operator to enter the profile of desired setpoint for the consolidated tablecloth 24

The processing unit 32 can be, apart from the improvements which will be described under the present invention, that already described in FR-A-2,770,855 to coordinate the operation of the card and the spreader. lapper for profiling the produced tablecloth

The installation therefore comprises connecting means 34 between the processing unit 32 and the card 1 for controlling the card 1 from the processing unit 32, and a bidirectional link 36 between the processing unit 32 and the spreader-lapper 2 for controlling the spreader-lapper 2 from the processing unit 32.

FIG. 6 shows points P _α to Pic corresponding to nineteen measurement points distributed over the width of the measurement station 28, as well as sections of the sail.

Ei to E. - distributed over the length of the veil deposited by a cycle of back and forth movement cnarict lapper 19 of 1 spreader-lapper. Each sail section Ξ _x to E _i7 coincides with the respective one of the measurement points P to F. _s . The extreme measurement points P ₁ and P _1Q are each located just beyond a respective one of the edges of the set profile and therefore do not correspond to any section E of the web. The measurement points P ₂ and P ₁₈ are located very close to the respective edge of the setpoint profile. Profile regulation will have, among other things, the goal that each edge of the real profile detected is maintained between the measurement points P _x and P ₂ for the left edge and respectively between the measurement points P ₁₈ and P ₁₉ for the edge law.

Another aim of the profile regulation will be that the surface weight recorded at each of the measurement points P ₂ to P ₁₈ is as close as possible to that resulting from the set profile at this point.

FIGS. 3 and 4 illustrate that a rectangular profile of the intermediate ply 16 (FIG. 3) tends in general after needling to give a profile with thickened edge zones 37 (FIG. 4), completely undesirable if the user wishes manufacture a consolidated sheet as uniform as possible, for example with a target profile as illustrated in FIG. 7. Obtaining a profile as close as possible to the target profile of FIG. 7 generally requires the manufacture of 'an intermediate ply 16 having the profile shown in Figure 8 that is to say with side edges tapering. This is preferably achieved by thinning each segment of veil as already described with reference to FIG. 5 in connection with the zones Z _τ and

Z ₂ . FIG. 9 illustrates by way of example a certain length of web 6 corresponding to a movement cycle of the lapping carriage for obtaining such an intermediate web profile, the different web sections E ₂ to E ₁₇ intended to correspond at the measurement points P ₂ to P ₁₈ also appearing in this figure. FIG. 10 is an example of a flow diagram for the implementation of the regulation method. This begins with a step 41 of reading the setpoint profile defined by the setpoint values P _2c , ..., Pie _c . expected for the measurement points P ₂ , ...; P _ιe respectively, then a reading step 42 of the real measurements P, ..., Pic Then we verify by two successive comparisons 43 and 44 that P- is indeed equal to 0 and P ₂ is much greater than C, in other words, that the left βord of the real profile is well located between the measurement points Pi and P _^ If the answer is yes to these two comparisons, go to a step 46 of updating and if necessary the correction of the surface weight e-. of the web in section E ₅ by applying the expression: e-, = e ₅ + 2 (P _2c - P ₂ ) / S expression in which e5 is the surface weight of the web in section E5 and

S is the number of veil segments superimposed in the thickness of the tablecloth The correction is distributed over all the cycles of movement of the lapping carriage, hence the division by S for the elementary correction As a movement cycle of the lapping carriage produces two superimposed segments of which only one will be corrected, it is nevertheless necessary, in this example, to double the thickness correction term as it appears in the formula above Figure 6 clearly shows why, with the correspondence system which has been chosen, the correction of the surface weight at point P ₂ of the web requires correcting the section E ₅ of the web.

We then go to two comparisons 47 and 48 to verify that the measurement P _ιS is much greater than 0 and the measurement

Pis is indeed equal to 0, in other words that the right edge of the sheet is well located between the measurement points P ₁₈ and P ₁₉ If yes, the surface weight eι ₄ at the measurement point Pι _B is updated and if necessary corrected in a step 49 consisting in applying a formula similar to that of step 46 but involving the difference between the target surface weight Pι _8c and the detected surface weight P _ιa Then we go to a step 51 of updating and if necessary correction of the surface weights for all the other sections of the wall 6, in a step 51 with, for each point, application of a formula similar to that described in step 46 as a function of the difference noted at the point of corresponding measurement A correspondence step 52 is then carried out consisting in recalculating, for reasons explained below î) the position occupied by the lapping carriage when the sail section being worked by the agency member ment (comber 21) is that intended to be on the axis of the ply 24, n the new length of sail to be produced between two successive passages of the carriage lapper by this position, and 111), the position of the sections E ₁ ; ..., E ₁₇ over this length.

The new values of e _α to e _± - are each transmitted at the desired time to the card 1 by the link 34 (FIG. 1) so as to give at each instant to the motor 52 driving the painter 21 (FIG. 5) the speed desired to achieve the corresponding surface weight e.

If the answer to one of the comparisons 43 or 44 is negative, the software performs a step 53 of repositioning the lateral edges of the sheet and in particular of the left edge of the sheet by applying the formula (L _NG = L _NG ± Δ L _NG ) so as to tend to bring the left edge of the sheet between the measurement points P ₂ and P ₂ . In this formula ^•

L _NG is the position of the left edge of the tablecloth; and ΔL _NG is the variation applied to this position

The software then goes directly to step 51, therefore bypassing the updating steps 46 and 49 of the surface weights at the edges of the sheet since these edges or at least one of them has proved to be badly positioned. We then go to the matching step 52, since the repositioning of the edges of the web has generally modified: î) the position of the lapping carriage for which the sail section passing through the layout member is intended to be positioned in the center of the ply, and / or n) the length of the superimposed veil segments making up the ply, as well as in) the position of the sections E ₁ to E ₁₇ along the veil.

If the result in one or other of the comparisons 47 and 48 is negative, one is also sent to step 53 for the calculation of a new position of the right edge of the sheet (Lm, = L _NR ± Δ L _NR ), formula in which:

LNR is the position of the right edge of the tablecloth; ΔL _NR is the variation applied to this position. We then go to step 51, having short-circuited step 49 of updating the surface weight e _i4 at the right edge αe of the sheet, then to step 52 of correspondence.

The updated values L _NG and L _NR calculated in step

51 are converted into commands transmitted by the processing unit 32 to the spreader-lapper 2 via the link 36 to move the limit switches of the lapper carriage 9 (FIG. 5) of the spreader-lapper in a corresponding manner After step 51, and after sufficient time has passed for the consolidated web 24 passing through the measuring station 28 to be affected by the changes ordered in the card 1 and / or in the spreader-lapper 2 as a result of the execution of the software which has just ended, the software returns to the reading step 41.

FIG. 11 illustrates a reference profile comprising two flat zones 57 of different surface weights separated by a progressive connection zone 58 FIG. 12 illustrates the profile of the intermediate ply 16 which will then be obtained by applying the method

The invention also relates to an initialization method intended to give the processing unit 32 a precise knowledge of the position which will be taken in the width of the web by a section of sail in tram to undergo the effect of the 'Organizer which is decisive for the surface weight of the veil produced. In the example chosen, the fiber arrangement member is the doffer 21 and the section undergoing the determining effect for the surface weight of the veil is the section designated by the reference 59 in FIG. 5. In d In other words, the efficiency of the process requires knowing exactly where this section 59 will be positioned in the width of the ply 16.

For this, the initialization step comprises on a section of the veil the production of voluntary faults, or

"pseudo-faults" each time the cart-napper 9 passes through a determined position of its movement cycle back and forth. The faults 61 are all found in the same position relative to the width of the intermediate ply 16, as illustrated at 62 for an axial defect in FIG. 13, and this results in a longitudinal defect 63 after needling (FIG.

14). More particularly, this fault 62, initially off-center as shown in FIGS. 3 and 4, is detected at the measuring station 28 and the processing unit 32 sends to the card 1 a signal producing a phase shift of the faults 61 until the pseudo-defect 63 is on the axis 64 of the consolidated tablecloth

24. At this stage, the processing unit 32 has identified with precision the position of the lapping carriage 9 when the sail section located in position 59 is a sail section Ei, intended to be on the axis αe la tablecloth The positions of the lapper carriage 9 when the other sections E ₂ to

E ₁ pass to position 59 can be deduced therefrom After initialization, the processing unit 32 detects predetermined positions of the lapping carriage 9 as indicators of the presence of a respective one of the sections

Ei, ..., Ex- in position 59 where the local surface weight of the wall is adjusted

In the above examples, the regulation of the transverse profile of the ply normally has the effect of regulating the longitudinal profile along each longitudinal line of the consolidated ply 24 corresponding to one of the measurement points P2 to P18 In other words, the surface weight will be regulated to a respective constant value along each line P2 to P18.

However, if one acts on the speed of the doffer 21, one must at the same time adapt the speed of the web at the exit of the card. These variations in speed do not pose any problems if the average speed of the doffer is constant, because they can then be compensated by a law of displacement different from the accumulator carriage 13 of the spreader-lapper. 21 result in a variation of its average speed, this results in the need to adapt the speed of the output belt 8 of the spreader-lapper and therefore the speed of all the machines located downstream.

If one wishes to avoid such a variation of the average speed of exit while regulating a parameter modifying the instantaneous speed at the exit of the carding machine, one can make so that the instructions e _2c ; ...; eι _8c are fixed not in absolute value but in percentage. But then the regularity of the longitudinal profile is no longer guaranteed.

The example in Figure 15 overcomes this drawback. It will only be described for its differences from the previous examples. The processing unit 32 calculates the sum e _s of the surface weights el; ...; el7 detected to raise the profile of the sheet. In the event of a difference between the sum e _s and a setpoint, the processing unit 32 controls by a link 71 a longitudinal regulator 72 placed between the loader 73 and the input of the card 1 to adjust the mass flow rate of f nres at the entrance of the card. We will thus adjust the average weight of fibers delivered by the card per unit of time The regulator

72 can be a weighing belt known per se or a device operating by density measurement using X-rays, also known per se The regulator normally has the function of controlling the input organs (the "food") of the carαe to ensure consistency αe production αe regardless of variations in certain fiber parameters. According to the invention, the unit 32 modifies an operating instruction of the regulator 72 to correct the differences in average surface weight observed at the output of the needling machine.

In the case where the transverse profile setpoint is a uniform profile as shown in FIG. 7, one could base the regulation of longitudinal profile not on the sum of all the surface weights, but on only one of them, or on the sum of only a few of them.

Thus, in the example represented in FIG. 15, the transverse profile is regulated by adjusting the instantaneous speed of the doffer so that its average speed over a movement cycle of the lapping carriage is constant, and independently of this, the profile is regulated longitudinal by adjusting the flow of fibers at the inlet of the card. The independence of these two regulations does not exclude, as we have seen, the use of the same detection for the evaluation of the results obtained on the consolidated sheet. Of course, the invention is not limited to the examples described and shown.

The invention is compatible with the other means for varying the surface weight of the web upstream of a spreader-lapper described in FR-A-2 770 855. Other reference profiles than those of FIGS. 7 and 11 can be made, with several flat zones separated by shoulders, or any other irregular shape desired, symmetrical or not, within the limit of the precision allowed by the number of measurement points and by the ability of the veil to suddenly pass a weight surface to another by varying the speed of rotation of the doffer 21 or any other means included in the card 1 and / or the spreader-lapper 2 to adjust the surface weight of the veil produced.

The embodiment of FIG. 15 is applicable when the transverse profile is adjusted by means of a variation of the speed of the lapping carriage on either side of a constant average speed.

Claims

CLAIMS 1- Method for regulating the transverse profile of a nonwoven web in an installation for producing said web from a fibrous product (6), in which a physical quantity is detected at a measurement station (28) of the sheet and depending on the detection, the profile of the sheet is corrected by adjusting an operating parameter of at least one fiber arrangement member (9, 21) located in the installation upstream of the measuring station, characterized in that - at the measuring station (28) the physical quantity is detected at several points (Pi, ..., P ₁₉ ) of the width of the sheet (24) so as to take up a transverse profile of the sheet;

- In the event of a deviation between the raised profile and a set profile, the operating parameter is corrected, when said arrangement member (9, 21) works the fibers which will be at the point of the width of the sheet where the profile deviation appeared.

2- A method according to claim 1, characterized in that the instantaneous profile is noted downstream of a consolidation machine (3) of the sheet, in particular a needling machine, and said arrangement member (21) which is modified the adjustment is located upstream of the consolidation machine (3). 3- Method according to claim 1 or 2, characterized in that the measuring station (28) is located downstream of a spreader-lapper (2) belonging to the production installation.

4- Method according to claim 3, characterized in that said at least one member (9, 21) whose setting is changed belongs at least in part to 1 spreader-lapper (2), and in particular comprises a lapper carriage ( 9) whose speed of movement is adjusted relative to the speed at which the fibrous product (6) leaves this carriage (9), so as to more or less stretch or compress the fibrous product (6) at the outlet of the carriage lapper (9).

5- Method according to claim 3 or 4, characterized in that said at least one member (9, 11) whose setting is changed belongs at least in part to a sail production machine, in particular a card (1) installed in the production installation upstream of the spreader-lapper (2). 6- A method according to claim 3, characterized in that said member (21) whose setting is changed is located upstream of one spreader-lapper (2).

7- A method according to claim 5 or 6, characterized in that one takes into account a rule of correspondence between the longitudinal position of the fibers (6) being worked by said member (21) and the future transverse position of these fibers in the sheet (24).

8- A method according to claim 7, characterized in that to establish this correspondence rule, an initialization step is carried out using a feature (61) of the fibrous product whose longitudinal position is identified along the fibrous product when passing through said member (21) and the transverse position (63) in the produced web (24).

9- A method according to claim 8, characterized in that said transverse position is identified by means (28) also serving to detect said physical quantity.

10- A method according to claim 8 or 9, characterized in that said aforementioned feature is carried out in the form of a local feature (61) of the longitudinal profile of the fibrous product (6).

11- A method according to claim 10, characterized in that one realizes the local particularity (61) using said member (21).

12- Method according to one of claims 8 to 11, characterized in that repeating the appearance of the feature (61) on the fibrous product (6) by shifting its longitudinal position on the product until the particularity has a predetermined transverse position, in particular a central position, downstream of the spreader-lapper (2).

13- Method according to one of claims 7 to 12, characterized in that the position of the lapping carriage (9) of the spreader-lapper (2) is identified in its reciprocating movement cycle when the particularity (61) passes through the arrangement member (21), then the correspondence rule consists in using the position of the lapping carriage (9) as a reference for the transverse positioning that each section of fibrous product will take in the sheet ( 59) in the process of passing through the arrangement member (21).

14- Method according to one of claims 3 to 13, characterized in that in case of deviation between the width of the profile reading and the width of the setpoint profile, the end positions (L _NG , L _œ ) of the lapping of the spreader-lapper (2) are corrected.

15- Method according to one of claims 1 to 14, characterized in that after having made a profile correction is corrected (52) a rule of correspondence between the longitudinal position of the sections of fibrous product (59) passing through the arrangement member (21) and their future position in the width of the ply (24).

16- Method according to one of claims 1 to 15, characterized in that the average surface weight of the ply is evaluated and in the event of deviation an input flow rate of the fibers is adjusted upstream of the arrangement (9, 21).

17- A method according to claim 16, characterized in that adjusts the input flow of fibers into a card (1) by means of a longitudinal regulator (72).

18- A method according to claim 16 or 17, characterized in that the average surface weight is evaluated by adding the values of said physical quantity in at least part of said points of the width of the sheet. 19- Method according to one of claims 1 to 15, characterized in that the average value of the adjustment parameter of the arrangement member is varied, in particular the average speed of rotation of a doffer (21) card, for a longitudinal profile regulation. 20- Installation for producing a sheet of nonwoven fibers, comprising fibers arrangement members (21, 9), detection means (28) for measuring a physical quantity of the sheet (24) moving at a measuring station, and control means (32) receiving a signal supplied by the detection means (28) and delivering to at least one of the arrangement members a modified control signal in the event of a difference between the quantity physical read and a set value, characterized in that:

- The detection means (28) are designed to measure the physical quantity at different points (P _!, ..., P ₁₉ ) of the width of the sheet (24); and

- The control means compare the physical magnitude of each point with a setpoint relating to this point, and in case of deviation at a point apply a corrected command when the arrangement member (21) works fibers intended to be at said point. 21- Installation according to claim 20, characterized in that the detection means (28) are placed downstream of a consolidation machine (3), in particular a needling machine, and said at least one arrangement member (21) fiber is located upstream of the needle loom (3).

22- Installation according to claim 20 or 21, characterized in that said at least one arrangement member (21) belongs at least in part to a sail production machine, in particular a card (1). 23- Installation according to claim 22, characterized in that the sail production machine (1) is upstream of a spreader-lapper (2) itself located upstream of the consolidation machine (3).

24- Installation according to claim 20 or 21, characterized in that said at least one arrangement member (9) belongs at least in part to a spreader-lapper (2), and in particular comprises a lapper carriage (9) whose the ratio between the speed of movement and the speed at which the fibrous product (6) leaves this carriage (9) is adjustable, so as to more or less stretch or compress the fibrous product (6) at the outlet of the lapping carriage ( 9).

25- Installation according to claim 22, characterized in that said at least one arrangement member comprises:

- A first arrangement member (21) belonging to a sail production machine, in particular a card (1), mounted upstream of the consolidation machine (3), to adjust the specific weight of the web at different points of its width; a second arrangement member constituted by a lapping carriage (9) of a lapping spreader (2), located between the card (1) and the consolidation machine (3), and the stroke ends of which (L _NG LN _R ) are adjustable to adjust the width of the ply (24).

26- Installation according to one of claims 20 to 25, characterized in that it further comprises longitudinal profiling means (71, 72) for regulating the average surface weight of the consolidated sheet to maintain this weight substantially constant according to the longitudinal direction of the tablecloth. 27- Installation according to claim 26, characterized in that the longitudinal profiling means comprise means (72) for adjusting the weight of fibers introduced into a card (1) upstream of the arrangement member (9, 21).