Glass manufacturing – Processes of manufacturing fibers – filaments – or preforms – Formation of fiber or preform utilizing fluid blast
Reexamination Certificate
2000-03-13
2003-03-25
Derrington, James (Department: 1731)
Glass manufacturing
Processes of manufacturing fibers, filaments, or preforms
Formation of fiber or preform utilizing fluid blast
C065S455000, C065S520000, C065S458000
Reexamination Certificate
active
06536241
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of the manufacture of mineral fibres from a drawable material and in particular from a molten material with a high melting point, for example of basaltic glass or blast furnace slag type, for the purpose of the production of products, in particular insulating materials, based on mineral fibres. More specifically, the invention relates to an improvement to the so-called free centrifuging fiberizing techniques, in which techniques the material to be fiberized is conducted in the molten state to the periphery of centrifuging wheels and is entrained by these wheels so that a portion of the material is detached therefrom and is converted into fibres under the effect of centrifugal force and so that the remaining unconverted portion is conveyed to another wheel or, after the final wheel, falls to the ground in the form of shot.
2. Discussion of the Background
Use is generally made, for the implementation of the fiberizing techniques briefly restated above, of a machine comprising three or four wheels arranged in cascade and capable of rotating about substantially horizontal axes, two successive wheels on the path of the molten material rotating in opposite directions. The first wheel is fed with molten material via a spout and serves essentially to accelerate the material, which is conveyed to the second wheel and thus in succession to the final wheel, the flow of material diminishing at each wheel in proportion to the amount of fibres formed.
Such a machine generally comprises, in addition, means for generating a stream of air at the periphery of the centrifuging wheels for the purpose of assisting in the formation of the fibres by an effect of drawing and of picking up the fiberized material, separating it from the non-fiberized material (shot). This is because the latter is undesirable as it contributes to making the final product heavy and to making it particularly unpleasant to the touch. The air stream also has the function of conveying the fiberized material to a gathering device, for example a conveyor belt equipped with extraction boxes, which transports the fibres to the treatment devices downstream of the line, such as a lapper, an oven for polymerizing the binders, and the like.
The air stream is generally introduced in a direction substantially parallel to the axes of rotation of the wheels and thus entrains the fibres in a direction perpendicular to their direction of formation.
The amount of fibres manufactured depends on the flow rate of material poured onto the centrifuging wheels and on the efficiency of the fiberizing by the said wheels.
For a given machine, it is possible in theory to increase the productivity by increasing the flow rate of poured material but this can only be carried out within a relatively restricted margin. This is because a machine is designed with wheels of defined diameters intended to rotate at a predetermined speed. Beyond a certain flow of material feeding the machine, the centrifuging wheels gradually become clogged up, with direct harmful consequences on the quality of the fiberizing (due in particular to the modification of the temperature on each wheel and to the excess material to be treated by each wheel).
This fall in quality is reflected in the final product by a loss in properties, in particular in thermal insulation properties: it is only by increasing the relative density of the product that the desired value of the thermal conductivity coefficient lambda (&lgr;) is achieved. The advantage resulting from the increased productivity is therefore found to be at least reduced thereby, if not completely nullified.
One alternative consists in using several fiberizing devices operating in parallel. The solutions provided to date nevertheless all have a certain number of disadvantages.
In a first known prior implementation of U.S. Pat. No. 3,709,670, two different sets of centrifuging wheels are placed side by side in the same vertical plane in the body of the same machine comprising two spouts for feeding with molten material. The two sets differ in that the first is the exact mirror image of the second with respect to a vertical axis, like its reflection in a mirror, two wheels at the same level rotating in opposite directions. This symmetrical arrangement is intended to prevent the air streams respectively emitted by each combination of centrifuging wheels from interfering with the other.
The major disadvantage of this symmetrical arrangement is economic in nature, because it is necessary permanently to have available two different sets of spare components and to carry out the maintenance and upkeep of two machines with different structures.
Another implementation is known from WO-A-92/06047, which is targeted at mitigating this disadvantage, where two identical fiberizing machines are placed side by side and fed in parallel with molten material. The machines are provided with air-blowing means, in combination with each of the centrifuging wheels, which generate an air stream close to the periphery of the wheel, the air stream having an axial movement component sufficient to take the fibres far from the fiberizing region and a tangential component sufficient to prevent interactions between the adjacent air streams.
To this end, the blowing means are composed of a drawing lip which borders the periphery of the wheel over a predetermined angular sector and within which are positioned air deflection fins inclined at an angle corotational with the rotation of the wheel, so as to direct the blown air with a tangential component which varies along the lip.
Such blowing means are also employed in the known device of WO-A-92/12940, which itself also comprises at least two identical fiberizing machines placed side by side and fed in parallel, in which machines the centrifuging wheels are small in diameter and have very high rotational speeds.
This arrangement of the blowing means nevertheless has the disadvantage of being complicated as it requires retaining an air stream adjusted to each of the centrifuging wheels. However, the deflection fins are sensitive components, in particular sensitive to vibrations due to the rotation of the wheels, which vibrations increase as the rotational speed increases. In addition, the deflection fins are exposed to being sprayed by shot with the risk of their inclination being affected in a way harmful to the direction of the air stream.
SUMMARY OF THE INVENTION
The aim of the present invention is to overcome these disadvantages and to provide novel means for making possible the production on a large scale of a product based on mineral fibres of good quality.
In this respect, the subject-matter of the invention is a process for the manufacture of mineral fibres, in which process at least two fiberizing machines placed side by side are simultaneously fed with material to be fiberized, each machine comprising a series of centrifuging wheels arranged in cascade and driven in rotation about axes all having substantially the same direction (so-called main axis), two consecutive wheels of the cascade rotating in opposite directions, the material to be fiberized being poured in the molten state into each machine at the peripheral surface of the first wheel, by which it is accelerated and is conveyed onto the second wheel and, optionally, successively onto the other wheels of the series, in order to be converted into fibres under the effect of the centrifugal force, and in which process the fibres formed by the various wheels of a machine are picked up by a gas stream, preferably emitted in a direction essentially parallel to the main axis of the said machine, and collected by a gathering device, characterized in that the main axes of two adjacent machines are positioned along a non-zero angle, this angle or each angle being adjusted in order for two gas streams emitted by the two adjacent machines to meet and combine.
This is because the inventors have demonstrated the fact that when the blowing gas emissions from two
Debouzie Alain
Dupouy Valerie
Derrington James
Isover Saint-Gobain
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