Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/04—Manufacture of glass fibres or filaments by using centrifugal force, e.g. spinning through radial orifices; Construction of the spinner cups therefor
  • C03B37/05—Manufacture of glass fibres or filaments by using centrifugal force, e.g. spinning through radial orifices; Construction of the spinner cups therefor by projecting molten glass on a rotating body having no radial orifices
  • C03B37/055—Manufacture of glass fibres or filaments by using centrifugal force, e.g. spinning through radial orifices; Construction of the spinner cups therefor by projecting molten glass on a rotating body having no radial orifices by projecting onto and spinning off the outer surface of the rotating body

Definitions

• This invention relates to a method of producing fibres from mineral melt with the aid of centrifugal force.
• the method is especially directed to controlling vibration conditions on the fibre producing surface/s of a spinning wheel unit employed for producing fibres from mineral melt.
• the invention is described below in connection with a so-called cascade spinner, but it can also be used with all prior art defibration methods where the centrifugal force plays a determining role at the initial stage of the fibre generation.
• a cascade spinn ⁇ er normally consists of two to four spinning wheels, each forming a unit with a driving axle, devices for the supp ⁇ ly of air, cooling agent, binding agents and possible other additives.
• the spinning wheels are normally installed onto a movable carriage.
• Fibre generation takes place as follows: the mineral melt is supplied onto the peripheral surface of the first spinning wheel unit from which it is thrown in a drop cascade form onto the next spinning wheel located at a slight angle below and from there onto the peripheral surface of the next and subse ⁇ quent spinning wheels.
• the number of spinning wheels is usually four, but it may be more or less.
• the mineral melt fixes onto the peripheral surface of each spinning wheel in a ribbon form. Fibre embryos are thrown out of this melt ribbon and are drawn into fibres with the aid of jets of air.
• the fibres are collected onto a receiving conveyor and are formed into a mat.
• the said uncertainty factor caused by the spinning wheel suspension can be essentially eliminated by providing the spinning wheel with non-contact magnetic bearings.
• This enables the control of the spinning wheel's rotation movement and allows the rotation of the spinning wheel or wheels with the centre of mass as the rotation centre.
• This is due to the fact that the centre of mass is shift ⁇ ed from the centre of the wheel as a result of the un ⁇ steady distribution of material around the spinning wheel - one of the results of fibre generation process.
• This .imbalance cannot be eliminated when using mechanical spinning wheel bearings; instead, the vibration caused by the difference between the centre of mass and the rota ⁇ tion centre will continuously disturb the fibre gener- ation process.
• the vibration directed at the melt surface causes a wave phenomenon with the peaks serving as embryos for the fibres being generated.
• the main pur ⁇ pose of this invention has been to conceive a method for controlling this wave phenomenon.
• a primary precondition for the functioning is, however, that uncontrolled vibra ⁇ tions are entirely eliminated from the spinning wheel rotation movement.
• the essential step is to control the spinning wheel's magnetic bearings into a vibrationless basic rotation state where the rotation centre is located in the center of mass. Once this is accomplished, it becomes possible to control the spinning wheel vibrations and use them for regulating the distri ⁇ bution of the fibre being generated.
• the aim in fibre generation is to accomplish a distribution of fibres with a dominating thickness of 2 - 6 ⁇ m. The intention is to avoid the generation of thinner and thicker fibres re- spectively.
• the fibre generation is controlled by accomplishing con ⁇ trolled vibrations in the spinning wheel.
• These vibra- tions produced in the spinning wheel may be directed radially or axially and can be caused alternatively or simultaneously.
• the vibration amplitude is restricted to the magnetic bearing's degree of freedom; in practice this restriction is to approx. 1 mm.
• Fig. 1 shows a front view of a spinning wheel unit with the melt ribbon on the peripheral surface of the spin ⁇ ning wheel, and the spinning wheel's geometric centre and the centre of mass marked
• Fig. 2 a) - c) shows the invention's control alterna ⁇ tive where high frequency radial vibrations are direct ⁇ ed onto the spinning wheel
• Fig. 3 shows a schematic control system for a spinning machine in accordance with the invention including four spinning wheels (the control circuit for a possible fifth spinning wheel is drawn using dashed lines in the lower part of the figure) , and
• Fig. 4 shows a schematic control circuit for a spin ⁇ ning axle
• Fig. 5 shows a schematic end view of a spinning wheel with a control system for the magnetic bearings pro ⁇ vided with the corresponding descriptions of the con ⁇ trol circuit components in Fig. 4.
• Figure 1 shows a cascade spinner with each of the spinn ⁇ ing axles suspended using at least one magnetic bearing.
• the thickness of the melt ribbon on the spinning wheel's peripheral surface has, however, been exaggerated. It mainly shows the correct proportion of the ribbon thick ⁇ ness at different points of the peripheral surfaces and on different spinning wheels.
• the spinning wheels' geo- metric centre has been indicated with rp.
• the spinning wheel's centre of mass has been indicated with mp. It is .easy to see that the varying thickness of the melt ribbon on the peripheral surfaces and the pulsing melt stream into the fibre generation device cause a displacement of the mass centre.
• By using magnetic bearings for axle sus ⁇ pension the wheel's rotation axles are shifted from the geometric centre to the wheel's centre of mass. With this arrangement, steady and vibration-free rotation is achieved, which is the primary precondition for the method in accordance with this invention.
• Figure 2 a shows an example of the bearing's radial con ⁇ trol value in the direction of an opposite pair of coils (e.g. 61, 61 in figure 5) where the bearing during an axle revolv actively prevents load changes from occurring and keeps the rotation centre within the system's centre of mass (by changing the bearing forces on opposite sides of the axle) .
• FIG 2 b) shows an example of a high frequency vibration intended to be directed to the axle in the direction of an oppo- site pair of bearings.
• the control signal for one of the above axle's coil pairs in accordance with the figure 2 c) during the same revolv as shown in figure 2 a).
• the vibration ampli ⁇ tude on the y-axle is shown in mm.
• control system includes two main cat- egories of control; a control circuit for the spinning machine and separate control circuits for the spinning machine's spinning wheels.
• Fig. 3 shows a schematic control circuit for the spinning machine.
• the spinning machine's control device 31 is provided with continuous fibre generation variable data supplied to the system from the fibre process detectors.
• the fibre gener ⁇ ation variables indicate, among other things, the various properties of the melt, such as temperature, viscosity, surface tension, and other concrete fibre generation values from the end-product, etc.
• the control circuit supplies control information 33 with regard to tempera- ture, vibrations, positions, powers, etc.
• the spinning axle control circuits 32 also supply signals 35 to the spinning machine control circuit. These signals may indicate the load imposed by the melt cascade on the magnetic suspension, the power consumption of spindle drive motors, position data, etc.
• FIG 4 shows in schematic form the part of the spinning axle control circuits used for controlling the magnetic bearings which is thus of importance for this invention.
• the control circuit is drawn for an axle with two pairs of magnetic coils in each bearing.
• the magnetic bearing's control circuits are of prior art type and control the current fed to the magnetic coils 61 based on the signals received from position detectors 7 and 9. ⁇
• control circuit 21 In the radial bearing the control circuit 21 is combined with a balancing circuit 22 used for relaying the rotor rotation onto the retardation axle which is major import ⁇ ance for the generation of fibre from mineral melt on the peripheral surface of a spinning wheel.
• the axle cooperates with the spinning machine's other axles via the spinning machine control circuit (fig.3) .
• Control circuit 32' constituting a part of the control circuit 32 in figure 3 has been inserted between the regulating circuit 21 and balancing circuit 22.
• Control circuit 32' prepares signals for the spinning axles con- tained in the magnetic suspensions.
• the circuit is in continuous contact with the spinning machine control sys ⁇ tem 31, figure 3, receiving parameter value data from it.
• the regulating circuit 32' can accept weakened output signals for certain magnetic coils, but can also supply the magnetic coil with control signals for active vibra ⁇ tion of the fibre generating element. This active vibra ⁇ tion can be executed, for example, by amplifying the vol ⁇ untary vibrations or by modifying the counter-acting fre ⁇ quency.
• the signals handled by the balancing circuit 22 must not, however, be totally ignored, as the material distribution on the spinning wheel would cause an imbal ⁇ ance jeopardizing the whole fibre generation process. Variations of rotor stiffness are actively used for vi ⁇ bration control via the amplifiers' frequency control, but rotor speed variations are not used to a very large extent, as the speed variations are primarily used for fibre generation instead of for seeking critical fre ⁇ quencies.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Magnetic Bearings And Hydrostatic Bearings (AREA)

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• 1990
  • 1990-12-07 FI FI906046A patent/FI906046A/fi not_active Application Discontinuation
• 1991
  • 1991-12-09 WO PCT/FI1991/000377 patent/WO1992010435A1/en not_active Application Discontinuation
  • 1991-12-09 EP EP19920900947 patent/EP0560869A1/de not_active Withdrawn

Non-Patent Citations (1)

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