Glass manufacturing – Processes of manufacturing fibers – filaments – or preforms – With measuring – controlling – sensing – programming – timing,...
Reexamination Certificate
1999-08-26
2001-03-20
Hoffmann, John (Department: 1731)
Glass manufacturing
Processes of manufacturing fibers, filaments, or preforms
With measuring, controlling, sensing, programming, timing,...
86, 86, 86, 86
Reexamination Certificate
active
06202448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to methods of production of mineral fibers, in which a stream of melted material falls onto the periphery of a rotor which has an approximately horizontal axis and which distributes the melted material to other rotors, the rotors forming the fibers by centrifuging. It relates in particular to the formation of mineral wools based on glass compositions or based on blast furnace slag or basalt, according to the methods described, in particular, in patent applications EP-A-0 167 508 or EP-A-0 059 152.
2. Description of the Related Art
In these methods, it is important to control the position of the point of impact of the stream of melted material on the first roller, and to do this not only in the tangential direction of the rotors where the position affects all the subsequent impacts on the following rotors, but also in the axial direction. Two phenomena depend on this latter position. In a stable process, the temperature of the rotors in the axial direction is not homogeneous since the melted material greatly heats the impact zone whereas the adjacent zones remain colder. It follows that an uncontrolled axial displacement of the zone cools the melted material—on each rotor—and alters the fiber-drawing conditions markedly and rapidly. It therefore is essential that displacements of this type are performed under the control of the operator of the machine.
Furthermore, periodic displacement of the impact zone has a certain advantage since it permits the wear of the surface of the rotor to be distributed over the entire length in the axial direction. It is essential to precisely know the axial position of the melted material for this purpose.
Methods of optical measurement of a stream of molten material which is falling onto a fiber-drawing machine are known. Some of them relate to the determination and the stabilization of the position of a stream of molten material intended to produce fibers by a direct blowing of the melted material. observing the stream in question in the axial direction is possible in the process in question since the stream is sharply deflected and even disappears at the precise instant at which a burner, the axis of which is perpendicular thereto, produces the fibers.
In other methods, the stream of molten material on a fiber-drawing machine is observed by a CCD camera with the object of determining the width of the vertical stream, whereas radiation detectors are used to measure the velocity thereof. These two measures are performed with the object of calculating the flow rate of the material.
The person skilled in the art also knows of the use of CCD cameras to determine the position of objects and even, owing to mechanical, electrical and information systems, to control the relative position or relative displacement thereof. Opto-electronic observation systems have been developed specially for this purpose.
SUMMARY OF THE INVENTION
An object of the invention is to provide a method for determining the relative position of a stream of melted material in relation to a fiber-drawing machine, which is exact and reliable and independent of disturbances in production.
The measuring method and devices according to the invention must also permit the relative position of the stream of melted material in relation to the fiber-drawing machine to be controlled, either to keep it constant, or to modify it in a controlled manner.
The document DD-B-292 439 proposes stabilizing the relative position of a free-falling silicate-based melted stream, and of a fiber-drawing machine comprising, substantially, of a blowing nozzle which acts horizontally, i.e., perpendicular to the original direction of the stream. It follows that, downstream of the nozzle, all the material is entrained horizontally, and that it is thus possible to perform an optical observation, from the bottom to the top, to the end of the stream. The document thus describes a system in which the image of the stream of melted material obtained on a detector connected to the fiber-drawing machine by means of the observation system is kept fixed in relation to the detector by the action of mechanical means which displace the fiber-drawing machine.
The system in DD-B-292 439, comprising the detection of the position of the stream of melted material and the means for stabilizing the relative position thereof in relation to the fiber-drawing machine, is very specific to the fiber-drawing method in question. It cannot be extrapolated to a machine where the material falls successively onto several rotating cylinders, the approximately horizontal axes of which are parallel to one another.
The optical method of evaluating a stream of material during the fall thereof onto a fiber drawing machine, which is essentially intended to measure the flow rate, is described in European patent application EP-A-479 676, for example. A linear camera, known as a CCD (Charged Coupled Device), with a horizontal measuring direction, observes the stream of molten material, and two radiation detectors are placed one above the other and at a distance from one another which is precisely known. The measurements effected are the width of the stream and the time which separates the successive passage of a characteristic feature in front of each of the two detectors. This latter measurement provides the velocity, and the first measurement gives an indication of the section, the two elements combined providing, in turn, an assessment of the flow rate of the material in the stream which is falling.
The present invention proposes a process for obtaining mineral fibers from a thermoplastic material with a high melting point, consisting in the melting of the said material and the distribution thereof, in the melted state and in the form of a stream, onto a rotor of a fiber drawing machine which may comprise several such rotors. The position of the stream in relation to the rotor is determined in a direction approximately perpendicular to the vertical plane containing the stream, and in a horizontal direction approximately parallel to the vertical plane containing the stream, either by determining the position of impact of the stream on the first rotor by means of an optical measurement performed on the stream itself, or by the measurement of the position of the material in the melted state at the periphery of one of the rotors.
Preferably, the position of the stream in a direction that is approximately perpendicular to the vertical plane of the stream is determined by optical observation of the stream itself. On the other hand, the determination of the position of the point of impact of the stream on the first rotor from an optical measurement on the stream itself in a horizontal direction approximately parallel to the vertical plane of the stream is performed by calculation of both the result of the optical measurement and the known position of the starting point of the stream.
When the fiber-drawing machine used in the process according to the invention comprises several rotors and the measurement of the position of the material in the molten state is performed, this is preferably on the first or the second rotor, and thus, advantageously, by optical observation, the optical observations being performed by CCD cameras.
According to the invention, the result of the determination is used to control the position of the point of impact of the stream on the first rotor and the result of the determination of the relative position of the stream in one direction is used to control the relative displacement of the stream and of the fiber-drawing machine approximately in the same direction, and furthermore, the optical observation at the periphery of the rotor is used to determine the width of the melted material there.
The invention likewise relates to a device for obtaining mineral fibers from a melted thermoplastic material comprising a melting furnace, members for distributing a stream of molten material, and rotors intended to distribute the molten material and/or to centrifuge
Alliel Luc
Melinand Alain
Hoffmann John
Isover Saint Gobain
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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