EP0294290B1 - Process for winding under compression - Google Patents

Abstract

The invention relates to the packaging of strip products based on mineral fibres. It is proposed to bring the strip into a space delimited by 3 elements imparted with a movement causing the winding of the strip. The third of these elements, the compression roll driven at a speed of rotation which is a function of a predetermined programme using as parameters the length of the strip already unwound and the speed of the conveyor supplying the strip. The rolls obtained according to the invention are more cylindrical and there are no over- compressed regions. <IMAGE>

Description

The subject of the invention is an improvement to the processes for forming rolls from strips of compressible materials, in particular strips of felts based on mineral fibers intended for thermal and / or phonic insulation of buildings.

The strips of felt, made up of mineral fibers - in particular glass fibers - associated with a resin most often formo-phenolic, are used in a common way for the insulation of roof spaces, walls or floors. The thermal resistance of a material being proportional to its thickness, modern requirements lead to the marketing of increasingly thick products, from 7 to 16 cm or even 25 cm thick. Since, on the other hand, glass fibers with very low thermal conductivity have been recently developed which are particularly fine, it is necessary to condition felt strips of low density and increasingly thick.

Usually, the packaging consists in the winding under compression of the felt strip in order to form a cylindrical roll whose subsequent unwinding is prevented by means of a paper or plastic envelope. A device for implementing this method is for example described in the French patent document FR 2553744 or US-A-3991538. In such a device, the winding takes place in a space delimited by three organs: the feed conveyor, a vertical conveyor or roller whose contact surface with the felt forms with the feed conveyor an angle of the order of 40-80 ° preferably close to 60 ° and a steamroller progressively moved apart in order to increase as the winding progresses, the space available for the roller, and animated by a rotation movement in the direction contrary to the direction of advance of the vertical conveyor.

In accordance with the teaching of the abovementioned publication, the winding is more uniform over the length of the strip if the compression exerted by the felt does not result from a passive action, but on the contrary the movement of the compression roller is controlled according to a predetermined program so as to impose on each turn of wound felt a given thickness - preferably constant or decreasing slightly as the winding. The parameters retained for the program are preferably the length of the wound strip and its initial thickness.

By doing this, a more uniform compression is obtained over the entire length of the felt strip and, therefore, an increase in thickness after unpacking also more uniform, which makes it possible to operate with the maximum compression ratio tolerated by the product and offer less packaging.

In addition to the need for controlled compression, there is also the need for good felt tension in each of the turns. If the felt is not correctly stretched by the steamroller, we observe on industrial packaging lines the production of non-conforming rollers, whose diameter is greater than the nominal diameter or even non-cylindrical but frustoconical. These non-conforming rollers do not facilitate the subsequent packaging operations and in particular the creation of bundles - and the unloading thereof - by means of machines. In EP-A-238393 (published on 23.09.87 and having as a priority the French patent application 8603415), it has been shown that these difficulties are essentially due to the surface condition of the compression roller. In this publication, it is proposed to remove the sculpted coating of the rubber type, usually used for the compression roller and to provide for the latter an inorganic coating, resistant to abrasion and forming roughness. This coating preferably consists of a first layer of molybdenum deposited by schooping on which is also deposited by schooping, a second layer consisting of grains for example of corundum whose thickness does not exceed one millimeter. In addition to these small asperities, the contact surface with the felt preferably has regularly arranged sculptures, 2 to 10 mm deep and not more than 20 mm apart.

A compression roller thus produced has a longevity of more than 500 hours - compared to the 150 hours of operation generally obtained with rubber coatings. The wear is therefore much lower and the variations in the surface condition of the roller over time are much better controlled, so that it is possible to at least partially compensate for this by modifying the speed of the compression roller by relative to the speeds of the two conveyors, or in practice by accelerating the compression roller as proposed in FR-A-2553744.

However, the results are not yet perfectly satisfactory: the higher the speed of the compression roller, the more the shearing phenomena in the product and therefore the degradation thereof are increased. Such degradation, even contained within the tolerated limits, does not allow operation with constant parameters; or to automate fairly simply the subsequent operations of handling the rollers, it is essential that their dimensions are repeated identically.

In addition, the inventors have shown that the quality of the winding does not meet strict quality criteria even when the roughness of the compression roller is perfectly constant and that the compression is regulated in accordance with the teaching of the patent. FR-A-2553744 cited above. It was observed first of all that when high compression rates are applied to the product - while of course being limited to acceptable rates taking into account the compressibility of the mineral fiber felt and its elasticity - the felt initiation is more or less damaged, the compression roller delimiting the felt or peeling off the kraft paper covering intended to serve as a vapor barrier. To remedy this, it is necessary to reduce the compression ratio, and part of the advantages linked to the exceptional quality of the fibers are thus lost in terms of the process.

Another drawback is observed when winding thick felt strips - for example 160-200 mm - and short (4-7 meters long). In this case, the thickness of the last wound turn becomes significant relative to the diameter of the roller which then has a helical and non-circular section. If the installation of the roll retaining envelope is not perfectly synchronized - which cannot be systematically avoided due to the very rapid rates - the covering and gluing area of the envelope may coincide moreover with this yawning zone of the last wound coil, which creates weakness in the packaging.

The present invention relates to an improvement which does not have the aforementioned drawbacks, to the processes for forming rolls from strips of compressible materials such as in particular glass wool strips. According to this method, the strip of material is brought continuously into a space delimited by three organs animated by a movement causing the strip to roll up on itself, successively in contact with each of the organs, the first organ in contact with the belt being a feed conveyor (2) and the third of these organs being a compression roller moved in rotation and further moved according to a predetermined program in order to gradually increase the space available for the roller being formed, and the speed of rotation of said compression roller is a function of a predetermined program using as parameters the length of the strip already wound and the speed of the conveyor for feeding the strip (first member in contact with it) so that the speed curve of the compression roller obeys a function in staircases of the winding time, the speed of the compression roller is chosen to be lower than the speed of the supply conveyor during the phase of constitution of the core of the roller, then greater than said speed of the supply conveyor during the phase of winding proper. Preferably, during the final packaging and smoothing phase of the roller, the speed of the compression roller is again lower than the speed of the conveyor for feeding the strip.

The rolled up strip constituting the core of the roll preferably does not exceed 30% of the total length of the rolled up strip. On the other hand, the smoothing period preferably comes after the complete winding of the strip and corresponds to the placement of the protective envelope made of paper or plastic. This smoothing ensures a better conformation of the rollers and moreover allows the part of the pre-glued envelope to be properly applied.

By proceeding according to the invention, perfectly cylindrical rollers are obtained and above all remarkable by the quality of winding of the first turns of the felt, that is to say of the turns constituting the core.

― figure 1:

une vue schématique d'une enrouleuse pour la mise en oeuvre de l'invention.

― figure 2:

des vues d'une bande laine de verre en cours d'enroulement, lorsque la vitesse du rouleau de compression maintenue constante (schéma 2.1): pendant la phase de constitution du noyau (schéma 2.2), pendant la phase d'enroulement proprement dite (schéma 2.3) et pendant la phase de lissage (schéma 2.4).

― figure 3:

des schémas correspondant à ceux de la figure 2 mais avec cette fois une vitesse du rouleau de compression commandée selon l'invention.

― figure 4:

des schémas correspondant à ceux des figures 2 et 3 pour un autre mode de régulation de la vitesse du rouleau de compression.

― figure 5:

un 3ème mode de régulation de la vitesse du rouleau de compression.

Additional characteristics are described in more detail with reference to the accompanying drawing plates which represent:

- figure 1 :

a schematic view of a winder for implementing the invention.

- figure 2 :

views of a glass wool strip during winding, when the speed of the compression roller kept constant (diagram 2.1): during the phase of constitution of the core (diagram 2.2), during the winding phase proper ( Figure 2.3) and during the phase smoothing (diagram 2.4).

- figure 3 :

diagrams corresponding to those of FIG. 2 but this time with a speed of the compression roller controlled according to the invention.

- figure 4 :

diagrams corresponding to those of FIGS. 2 and 3 for another mode of regulating the speed of the compression roller.

- figure 5 :

a third mode of regulating the speed of the compression roller.

Figure 1 is a schematic view of a winder according to the teaching of French patent publication 2553774. The strip of mineral fibers, preferably glass wool, is produced in a manner well known in the art, for example by centrifugation of molten glass and gaseous drawing of the filaments formed. The fibers are impregnated with a thermosetting binder preferably before being collected by a vacuum conveyor which transfers the strip thus formed to a polymerization oven. On leaving the oven, the edges of the strips are cut and the strip is cut into sections of lengths and widths chosen according to the destination of the product. Optionally, a sheet of kraft or aluminized paper is glued to one side of the glass wool strip in order to form a barrier opposing the passage of water vapor. If the mode of manufacture of the fibers is in itself indifferent for the invention, it should all the same be noted that the light felts - whose density does not exceed 30 kg / m³ - are generally produced with very large pulls for example 160 tonnes per day of fiber. With such pulls, the speeds of the reel conveyors must be of the order of 100 meters per minute, sometimes reaching more than 120 meters per minute. This means that the winding of the glass wool strip and the packaging of the roll in a protective envelope must be carried out at the same rates, rates which quickly highlight all the defects of the process. It goes without saying that it is possible to use several rewinders, but the maintenance and labor costs are therefore multiplied.

The glass wool felt 1 is transferred to the supply conveyor 2 of the winder, preferably an endless belt driven by a motor 3 which transmits its power to the drum 4 by means of a transmission belt 5. The felt is thus conveyed in the direction of the arrow to a delimited space 6. Preferably, the conveyor 2 is equipped with a vacuum box not shown here which prevents the felt from sliding.

The felt then comes into contact with a second conveyor 7, forming with the supply conveyor 2, an angle between 40 and 80 ° and preferably of the order of 60 °. The movement of the conveyor 7 is also controlled by the motor 3 by means of a deformable transmission belt, shown below. The conveyor 7 can be retracted in the direction of the arrow "f", by rotation of its support arm 8 around the axis 9 by means of a jack 10 supported by the upper part of the chassis 11 of the reel so as to free the roller from space 6 after its packaging in a protective envelope, the roller then falling on the inclined plane 12 before being taken up by other conveyors for palletizing operations.

The frame 11 also supports two arms 13 framing the support arm 8 and between the ends of which are fixed two rollers 14 and 15, driven in rotation in opposite directions from each other, the roller 15 - called compression roller s' opposes the advancement of the felt 1 which it thus constrains to wind.

The arm 13, extended by counterweights 16, is moved by means of the arm 17 of a jack articulated on the support 19. On the other hand, the axis 20 of the arm 13 has an initial height adjusted by a motor screw 21.

Have also been shown schematically in Figure 1 the feed elements of the pre-glued protective envelopes which pass in a known manner from a conveyor 22 to belts 23 which deposit the envelope in the delimited winding space.

The aforementioned elements of a winder are given for illustration only and can be replaced by equivalent elements without departing from the scope of the invention. Thus, the vertical conveyor 7 can be replaced by a large diameter roller, although this is not preferred since the contact area with the felt strip is then reduced.

In accordance with the teaching of the document FR 2553744 already cited several times, the actuator 17 controlling the movement of the compression roller 15 obeys a predetermined program which uses as a parameter in particular the length of strip of felt already wound up, length identified at each instant by a sensor 24. Other sensors, not shown here, measure the position of the compression roller and the speed of the supply conveyor 2.

Also preferably and in accordance with the teaching of French patent application 8603415 cited above, the compression roller 15 has its contact surface with the felt covered with an inorganic abrasion resistant coating, forming roughness and preferably consisting of corundum grains deposited by schooping on a molybdenum support. Preferably, the contact surface with the felt is constituted by a series of bars screwed onto the roller and coated as indicated above. Such a compression roller adheres well to the felt, even coated with a vapor barrier, and moreover degrades only very slowly.

However, the authors of the present invention have found that the results are not always satisfactory even when operating with a compression law and with a compression roller having a good surface condition. An example of a fault has been reproduced for example in an exaggerated manner in FIG. 2.

Diagram 2.1 represents during the conditioning time of a felt roll the speed of the compression roller (line 25) and that of the vertical conveyor (dotted line 26). The ordinate values correspond to percentages of the speed of the supply conveyor; speed which as indicated above is measured at all times and serves as a reference. We operated here in accordance with the art with a vertical conveyor speed 5% higher than that of the feed conveyor and with a compression roller rotating with a constant speed equal to that of the feed conveyor.

Figure 2.2 shows an exploded view of the device in the winding area at the very start of it. The felt 1 progresses towards the zone 6 here reduced to its smallest dimension, the counter-roller 15 having not yet started to move apart. During its progress, the felt 1 first collides with the roller 14 which forces the felt towards the winding zone and compresses it strongly. As soon as it is no longer in contact with this roller 14, the felt, thanks to its resilience instantly regains part of its volume but is immediately taken up by the compression roller 15. As the latter rotates at the same speed as the supply conveyor 2, the surface layers of the felt tend to disintegrate, which is particularly damaging when the felt is provided with a vapor barrier coating. Note, however, that the compression action exerted by the roller 15 makes it possible to attenuate to a large extent this harmful effect.

As the winding progresses, the compression roller 15 is discarded as noted in diagrams 2.3 and 2.4. There is therefore no longer any fear of delittance. On the other hand, even if the attachment to the compression roller 15 is of good quality, the roller in the process of conformation has a slight tendency to follow the vertical conveyor 7, which is faster, and a point 27 is formed.

When the entire strip of felt is wound up (diagram 2.4) and the protective casing of the roll is applied, it can be seen that the roll has a second advance 28, imprint of the felt 1 conveyed by the feed conveyor 2. This advance 28 is due to the too low compression of the last coiled felt turn or to the too high speed of the compression roller.

Without forgetting, however, that the manifestations of the winding disturbances have been largely focused on these diagrams, we finally obtain a roller whose section is not circular but evokes a 3-pointed star. If this phenomenon is sufficiently marked, the felt sees its mechanical properties deteriorated by these deformations, in particular from the point of view of its resistance to fatigue and shear. In addition, the finished rollers may be slightly tapered, which poses handling problems. Another more serious drawback is that the felt is not compressed at all points in an identical manner, but has overcompressed zones whose thickness recovery after unpacking is less than that of the other zones. It is then necessary to modify certain settings of the production line either to play on the extra thickness given to the felt, or to increase its density or the fineness of the fibers used.

These drawbacks are eliminated if one proceeds in accordance with the invention as illustrated in FIG. 3. As indicated in diagram 3.1, the speed (curve 29) of the vertical conveyor 7 is kept constant and is 5% higher than the speed of the conveyor d 'lead 2 always taken as a reference value. On the other hand, the speed of the compression roller 15 (curve 30) is modulated as a function of the progress of the winding and of the speed of the reference conveyor.

In the simplest case shown here, the modulation is in three stages. From time 0 to time t₁, the speed V₁ of the compression roller is kept slightly lower than the speed V₂ of the supply conveyor 2. Good results are obtained with a speed V₁ equal to approximately 95% of V₂ during this first phase. As a result, the adhesion of the compression roller on the product is slightly lower even for very high compression rates; thus, we avoid deburring the front edge of the felt and possibly creasing the vapor barrier. The product is thus braked by the compression roller and it has the necessary time to roll on itself. Thus, during this priming phase, the core of the roller is formed, around which the following turns will be wound. During this initial phase, from 5% to 30% of the length of the wound strip.

From time t₁ to time t₂, the speed V₁ of the compression roller is appreciably increased and fixed between 105 and 110% of the speed V d'am of the supply conveyor. This speed variation can be obtained by associating with the reciprocating motor actuating the compression roller a frequency variator and an analog card controlling it. This alternating motor can be replaced by a DC motor with constant torque, the response time of which is advantageously faster. This second phase at faster speed ends at time t₃, when the entire strip is wound. As the core of the roll was perfectly formed in the first phase, strong compression of the turns is then possible without risk of malformation of the felt roll. In addition, this greater speed of the compression roller makes it possible to compensate for any slippage of the strip on the supply conveyor 2, slippage which could otherwise lead to the formation of folds.

At the end of this second phase, the strip 1 is completely wound up and the packaging of the roll is then carried out in a plastic envelope. In this third phase, the speed V₁ of the compression roller is again reduced to around 95% of the speed V₂ of the supply conveyor; therefore, the speed of rotation of the envelope is slowed down and the latter is stretched so that good smoothing of the felt roll is ensured. This also makes it possible to reduce the deformation of the rollers in the case of products of great thickness for which it is difficult to properly flatten the last turn. This final smoothing phase, from time t₂ to time t₃ preferably flows for a period corresponding to at least three complete rotations of the felt roll. This slowdown creates a significant difference between the speed of rotation of the felt roller and the speed of the compression roller, which promotes the evacuation of the felt roller by the inclined plane 12 as soon as the conveyor 7 is retracted.

As shown more particularly in diagram 3.4, the roll obtained is constituted by uniform turns, wound around generators of concentric cylinders.

To test the effectiveness of such a roll forming process, strips of glass fiber 11 m long, 1.20 m wide and 80 mm thick were wound. Rolls of 500 mm in diameter were formed, which corresponds to a compression ratio of 4.5. The strips are then unrolled, cut into squares. By proceeding in accordance with art (FIG. 2) or in accordance with the invention, in both cases, an average thickness recovery of 129% is obtained. On the other hand, the dispersion of the measurements is much greater in the first case (standard deviation 8.5) than in the second (standard deviation 6.8), which shows that the winding conditions are much more stable. On the one hand, it is possible to slightly reduce the grammage of the products, the thickness recovery should in no case be less than 105% of the nominal thickness and on the other hand, the rollers are much more uniform which simplifies the constitution of transport and storage burdens and handling by robots for example.

Previously, we have indicated that the speed of the compression roller varies according to the winding phases between 95 and 110% of the speed of the supply conveyor. These values are extremes as shown in diagrams 4.2, 4.3 and 3.4 in FIG. 4. The law of speed of the compression roller over time has again been represented (diagram 4.1). In the priming phase, the speed of the compression roller was chosen to be of the order of 90% of the speed of the supply conveyor. As shown in diagram 4.2, the felt strip does not then tend to roll on itself but on the contrary the strip adheres to the conveyor 7 and tends to come out of the winding zone. The front edge of the strip is subjected to high stresses, and a dense core is not formed for the rest of the operations. If in the second phase, the speed of the compression roller is very strongly increased and passes to approximately 115% of the speed of the supply conveyor, the adhesion of the compression roller is then extremely strong and the roller being formed has an almost triangular shape, a shape which is further accentuated in the smoothing phase if the speed of the compression roller is again considerably reduced (90% of V₂).

According to the exemplary embodiment of the invention proposed with the help of FIG. 3, the speed of rotation of the compression roller obeys a program in three stages: initial phase, winding phase, terminal smoothing phase. This is a simplified type of control of the speed of the compression roller but which already makes it possible to obtain a significant improvement in the quality of the winding. The applicant however prefers to operate in a slightly more complex manner, following the speed law shown diagrammatically in FIG. 5, with a minimum of 4 steps.

Initially (from 0 to T₁), the speed of the compression roller (initial speed) is preferably equal to 95% of the speed of the supply conveyor. As in the case illustrated in FIG. 3, this speed is maintained for the time necessary for the constitution of a core of the perfectly formed roller on which the following turns can be wound. For the strips of so-called short felts (4 to 7 meters), approximately 30% of the length of the strip is wound at this initial speed. For longer strips, the core is preferably formed by about the first two meters of the strip. The front edge of the felt strip does not undergo disintegration and any tearing or creasing of the vapor barrier is avoided.

We then pass to the actual winding phase which takes place in two stages. From time T₁ to T₂, the speed of the compression roller is chosen to be equal to or slightly higher (105%) than the speed of the supply conveyor, which allows a gradual increase in speed, a sudden acceleration that can be damaging to the felt. About 20% of the length of the strip is thus wound. This winding phase continues from time T₂ to T₃ until complete winding of the strip, operating with a high speed of the compression roller, between 105 and 110% of the speed of the supply conveyor. If a variable speed drive is available which allows it, the transition from the initial speed to this high speed by winding can be carried out not in a single stage (T₁ to T₂) but in a succession of stages, or even even continuously.

Once the strip is wound up, we pass to the packaging and smoothing of the formed roller, which is done with a slow speed of the compression roller, about 95% of the speed of the supply conveyor. At the end of this fourth stage, the compression roller can still be suddenly braked, which allows very precise fixing of the instant of ejection of the packaged roller.

The exact determination of these speed laws must be carried out for each type of product by specialized personnel. It is therefore advantageous to combine means of storage and automatic reminders of the different speed laws established. In addition, these laws may advantageously take account of a wear factor of the compression roller whose speed will be systematically reduced if its roughness is too sharp, which is the case with a new badly deburred roller and on the contrary increased when the coating of the roller becomes less adherent due to wear.

Claims (8)

1. Process for forming rolls from strips of compressible materials, in particular made of felt with a mineral fibre base, in which the strip of material (1) is continuously fed to a space (6) defined by three members (2, 15, 7) operated by a movement causing the coiling on itself of the strip which is in contact in turn with each of the members, the first member in contact with the strip being a feeding conveyor (2) and the third of these members being a compressor roller (15) which is displaced so as to increase progessively the space (6) available for the roll being formed and the rotational speed of the said compressor roller (15) being a function of a predetermined programme involving, as parameters, the length of the strip which has already been coiled and the speed of the conveyor (2) for feeding the strip such that the speed V₁ of the compressor roller (15) is less than the speed V₂ of the feeding conveyer (2) during the initial phase of the formation of the core of the roll, after which it is greater than V₂ during the coiling phase proper.

2. Process according to claim 1, characterised in that the speed V₁ of the compressor roller (15) is held at less than V₂ during the final phase of packing and smoothing.

3. Process according to claim 1, characterised in that the phase relating to the formation of the core of the roll corresponds at most to 30% of the length of the strip to be coiled.

4. Process according to claim 2, characterised in that the final phase of smoothing and packing is carried out after the strip has been completely coiled during the positioning of a protective covering of the roll.

5. Process according to claims 1 to 4, characterised in that during the initial phase, the speed V₁ is greater than or equal to 95% of the speed V₂.

6. Process according to one of claims 1 to 5, characterised in that during the coiling phase proper proper, the speed V₁ is at most equal to 110% of the speed V₂.

7. Process according to one of claims 1 to 6, characterised in that the coiling phase proper itself comprises at least two stages, an initial stage (from T₁ to T₂) with an increase in the speed of the compressor roller, V₁ being chosen between 100 and 105% of the speed of the feeding conveyor, corresponding to the coiling of approximately 20% of the felt strip, and a second stage (from T₂ to T₃) at high speed (between 105 and 110% of the speed of the feeling conveyor).

8. Process according to claim 7, characterised in that after the roll has been packed, the compressor roller is braked in such a way as to cause the ejection of the roll instantaneously.

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