FR2736940A1 - Appts. for making mineral fibre felt layers - has source of projected mineral fibre building up felt layer on inclined perforated transporter with improved suction under felt as it leaves working chamber. - Google Patents

Abstract

Appts. for making mineral fibre felt layers (49) consists of a source of projected mineral fibre (32) which builds up a felt layer on an inclined perforated transporter (34). The transporter passes through 3 zones including the upstream zone (35) where the heavy fibres collect, the middle zone (36) where the majority of fibres collect and a downstream zone (37) where the chamber forms a roof (47) running parallel to that of the felt layer. Under each zone is an independent suction device (38, 39, 40).

Description

METHOD AND DEVICE FOR FORMATION
OF AN IMPROVED QUALITY MINERAL FIBER FELT
The invention relates to techniques for manufacturing felts of mineral fibers and more particularly the reception of fibers on a perforated conveyor belt. It relates more specifically to the manufacture of mineral fibers in which the fibers leave the fiberizing device, entrained by a strong gas stream in a substantially horizontal direction. These are processes which disperse frozen glass filaments or a liquid glass net using a torch with a substantially horizontal axis or else centrifugal fiberizing on wheels with a horizontal axis with a circular air flow at the periphery of the wheels.

 In all these techniques, the mineral fibers, immediately after their preparation are coated with a liquid which, once dried and / or polymerized, will serve as a binder so as to join the fibers together to form a felt. To constitute this felt, the fibers are collected, as soon as they are formed, on a perforated conveyor belt through which the gases are sucked.

The enclosure within which these operations take place is the reception room.

 The invention relates to techniques where the perforated conveyor belt supporting the felt in formation is more or less inclined possibly up to the vertical, it drives the felt upwards. Such a device is used in particular when the manufacture of a thick felt is done in two stages, first the manufacture - thanks to a rapid displacement of the preceding inclined perforated conveyor belt - of a thin felt then, the deposition in zig zag in several thicknesses thereof, perpendicular to the movement of a second carpet, generally horizontal, which receives the mattress with its final thickness. Such a two-step process is described for example as a prior art known in patent application DE-A-35 01 897.

 The techniques of the invention also apply in the case of the direct manufacture of a thick felt on an inclined perforated conveyor belt through which the gases carrying the fibers from a spinner are drawn, the axis of which ejection is substantially horizontal.

 The invention relates to techniques for improving the quality of felts obtained on inclined carpets.

 The document EP-B-439 385 describes a device for manufacturing mineral fibers which comprises as a spinner, a system in which a thread of a molten vitreous material flows on a first drum with a horizontal axis rotating at high speed from where the liquid is projected onto a second wheel whose axis is parallel to that of the first and which forms fibers by centrifugation then possibly onto a third and even a fourth wheel which also generate fibers. Gas streams parallel to the axis wheels, at their periphery, with in addition an auxiliary gas stream which is created with substantially the same direction as the main gas stream, but which, it originates at a distance from the centrifuge wheels, entrain the staple fibers in a sort cone of irregular section but whose axis, like that of the drums, is substantially horizontal. The fiber cone is located in a closed chamber, one of the walls of which is formed by a conveyor belt, horizontal here. A suction system through the carpet attracts fibers which gradually accumulate on the carpet in translation.

 The document US Pat. No. 3,045,279 also describes a so-called free centrifuge spinner of the same type as above in which the receiving belt is inclined, it transports the fibers upwards, the gas streams and the suction which passes through the inclined collecting belt create in the chamber a general gaseous movement which carries the fibers into the cone mentioned above, the original contour of which is the outer perimeter of the spinner and which widens on its way to the receiving belt. Its intersection with the carpet constitutes the main area for gathering fibers. A few stray fibers are gathered outside this zone, and in particular, below, heavy fibers that are poorly centrifuged. The infibrated particles fall directly under the spinner without reaching the collecting belt.

 The document US Pat. No. 4,433,992 which also relates to a free centrifuge spinning machine of the most common type, that is to say with a horizontal receiving conveyor, has under it two separate suction devices which make it possible to have on two areas of the mat two different gas flows.

 Devices of the inclined receiving belt type are well known and, for the most part, they give satisfaction with one exception, the mattress once formed, on leaving the main area for forming the mattress, which is located at the intersection of the cone with the conveyor belt, deteriorates, tongues of fibers are torn off from the felt and roll up on themselves to form sorts of rolls which resemble cigars.

 The invention sets itself the task of improving known techniques and, in particular, of avoiding this phenomenon of constitution of cigars.

 The invention proposes an installation for manufacturing a mattress of discontinuous mineral fibers comprising in particular a fiberizing device where the fibers are projected in a conical sheet of substantially horizontal axis and comprising an inclined perforated conveyor belt and a gas suction device through of the belt, the conveyor belt constituting one of the walls of a receiving chamber, device in which the upper wall of said chamber has a part tangent to the conical sheet of the projected fibers and a part substantially parallel to the conveyor belt.

 This design of the ceiling of the reception chamber makes it possible to obtain gas streams which prevent the pulling out of tongues of fibers from the surface of the mattress downstream of the zone of formation of the mattress.

 Preferably, the distance between the part of the upper wall of the chamber parallel to the carpet and the latter is between 150 and 400 mm. Likewise, the device comprises downstream of the conveyor belt, preferably at the end of the zone bounded by the belt and the part of the upper wall of the chamber parallel to the belt, an air inlet orifice.

 To complete the installation of the invention, provision is made for the device for sucking the gases through the belt to comprise at least two separate suction areas, one of which acts mainly downstream of the impact zone of the fibers. . Preferably, these are three fields, one of which essentially concerns the impact area of the fibers and the other two of which are respectively, one upstream and the other downstream thereof.

 The installation of the invention is very simple to carry out, it allows, in particular when the three devices are present simultaneously, to obtain a mattress of regular thickness and which does not have on the surface, faults of the cigar type.

 The figures and the description will make it possible to understand the operation of the invention and to appreciate the advantages thereof.

FIG. 1 represents a reception chamber of the prior art,
- Figure 2 an embodiment of the invention.

 The techniques of the invention relate to the reception of mineral fibers immediately after their preparation, their ejection and, in general, their coating with a liquid intended to associate them definitively to constitute a felt or a mattress. This means that several modes of production of fibers can be used in the context of the invention. More specifically represented in the figures and described in the text, the technique known as free centrifugation but all the processes which end in the production of a stream of discontinuous fibers in the shape of a more or less regular cone with its axis in a direction close to the horizontal and with collection of fibers on an inclined perforated conveyor belt are suitable for the implementation of the device of the invention.

 In FIG. 1, we see, diagrammatically, a traditional installation for manufacturing mineral fibers with projection of the staple fibers with a direction of origin which is substantially horizontal. Here the fiberizing machine 1 is free centrifugation. We see in 2 the roller with horizontal axis which receives the net of molten material (not shown). This first roller returns the material to the second roller 3 where it is centrifuged, the rest being projected onto the roller 4 where the centrifugation continues. The staple fibers 5 are projected onto the inclined perforated conveyor belt 6. The latter drives the fibers upwards, in which direction the thickness of the mattress 7 increases. A box 8 placed under the carpet makes it possible to suck the gases through the latter thanks to fans not shown.

 The design of the reception chamber 10 of FIG. 1, with its flat ceiling 9 and its single box 8 does not prevent the formation of cigars, that is to say, tongues of fibers extracted from the mattress and rolled up on themselves.

 FIG. 2 shows an installation bringing together the devices of the invention.

 In the figure, there is shown the section of a receiving chamber which groups together the means of carrying out the invention. A fiberizing machine 31, here, also with free centrifugation, with its rollers, produces fibers which are projected in the form of a conical sheet 32 of axis close to the horizontal while the infibrated particles 33, less easy to entrain in the gas stream fall into a pit. The fibers are projected onto the perforated conveyor belt 34. This has three zones, an upstream zone 35, the lowest which receives the heaviest fibers and those which have strayed far from the cone 32, a central zone 36 where bring together the majority of the fibers and, finally, a downstream area 37, where, before the invention, the defect in cigars formed, windings of tongues of fibers torn from the surface of the mattress.

 The suction is done independently on each of the three zones 35, 36, 37 thanks to three separate extraction hoods, respectively 38, 39, 40 and three fans 41, 42, 43 each acting on one of the three zones.

This configuration, the most elaborate of the means of the invention comprises three zones. This design makes it easy to adopt the correct settings regardless of production conditions. In particular, when the draft varies, it is useful to be able to adjust each of the three zones separately. What is very important for the invention is to be able to independently adjust the suction in the upper zone, downstream of the fiber collection zone so that the suction is sufficient therein so as to give the gases to the surface. of the carpet already formed the direction and the speed which avoids the extraction of the tongues of fibers.

 A second element of the device of the invention is the roof 44 which is here, much lower than usual. In fact, it is usually horizontal, at the level of the downstream end of the conveyor belt, where the last roller 45 is. The roof 44 essentially comprises two parts, a substantially horizontal part 46 which tangents the conical flow 32 of the fibers and a second part 47, determining which is substantially parallel to the conveyor belt. Its role is to divert towards the downstream zone, that which follows the zone of formation of the mattress, part of the gases taken to the main current, that of the cone of the fibers 32.

 A third element which appreciably improves the results is very surprising, it is an air inlet orifice 48 at the end of the corridor which constitutes the space between the surface of the fiber mat 49 and the roof. 47. The role of the air stream which enters through the orifice 48 to be immediately sucked through the mattress 49 by the fan 43 is difficult to understand.

Perhaps it is a kind of lock which prevents any passage of gas beyond the corridor in zone 37. In any case, it appears that this air intake greatly favors the correct orientation of the air. in this area 37.

 Many attempts have been made to size the device of the invention and to find the limits of the process.

 With a free centrifugation fiberizing installation capable of producing 6 tonnes of rock fibers per hour, a perforated carpet with a width of 2.60 m inclined by 450 and which has a useful length of 7 m was installed. The distance between the centrifuges and the belt, measured on the axis of the fiber cone is 4 to 5 m.

 To determine the conditions necessary for the process of the invention, the gas flows through the different zones were evaluated from the conditions originally measured (gas flow and velocities) and the surfaces concerned (spinner, cone sections fibers).

 Zone 36 (impact of the fibers) collects the original gases and the air entrained by them.

When producing a 30 mm thick mattress with a density of 10 kg / m3, excellent results have been obtained with a ratio between the gas flow rates which is as follows
* zone 36: 100%
* zone 35: 25-35% of the previous
* zone 37: 25-35% of the same.

 In general, it has been found, under the conditions of FIG. 2 with three suction zones, that the results are excellent when the flow rate of the gases sucked into the zone downstream of the reception zone 37 is between 16 % and 22% of the total flow sucked.

 The air inlet orifice 48, for its part, allowed a flow of approximately 5 to 10% of the flow from zone 36 which are included in the 25 to 35% during the above tests.

 The corridor between the mattress 49 and the roof 47 has a length of less than 2.50 m, 1,750 mm has given excellent results. Its thickness is between 150 and 400 mm, in general, it decreases from bottom to top.

 The products obtained with the techniques of the invention are of excellent quality. Not only, there is no surface winding of fibers (absence of cigars) but the homogeneity of the product in thickness and in width as well as the distribution of the surface masses - and therefore thicknesses - over the width are excellent and well better than without the means of the invention.

Claims (5)

 1. Installation for manufacturing a mattress of discontinuous mineral fibers from a fiberizing device in a receiving chamber, the fibers being projected in a conical sheet of substantially horizontal axis and being received on an inclined perforated conveyor belt, the installation comprising a gas suction device through the belt and the conveyor belt constituting one of the walls of the receiving chamber, characterized in that the upper wall of said chamber has a portion substantially tangent to the conical sheet of the projected fibers and a part substantially parallel to the conveyor belt.  2. Installation according to claim 1, characterized in that the distance between the part of the upper wall of the chamber parallel to the belt and the latter is between 150 and 400 mm.  3. Installation according to claim 1 or 2, characterized in that it comprises downstream of the conveyor belt, preferably at the end of the channel formed by the belt and the part of the upper wall of the chamber parallel to the belt, a outside air inlet.  4. Installation according to one of claims 1 to 3, characterized in that the gas suction device through the belt comprises at least two separate suction areas, one of which acts mainly downstream of the area of impact of fibers.  5. Installation according to claim 4, characterized in that the gas suction device through the belt is separated into three areas, one of which essentially concerns the impact zone of the fibers and the other two of which are respectively, l 'one upstream and the other downstream of it.