A METHOD OF CONTROLLING FIBRE GENERATION IN THE MANUFACTURE OF MINERAL FIBRES FROM MINERAL MELT WITH THE AID OF CENTRIFUGAL FORCE AND AN APPARATUS FOR THE IMPLEMENTATION OF THE METHOD

Abstract: The invention relates to a method for contolling fibre generation in the manufacture of fibres from mineral melt using several cooperating rotating wheels within a defibration unit. The melt route over the wheels is controlled by changing the position of one or more of the rotating wheels (1-4) within a defibration unit on the basis of the various factors affecting defibration process. The control may take place in such a manner that all rotating wheels are turned as a rigid entity around an axle parallel with the rotating wheel axles. Alternatively, one or more wheels are controlled individually in relation to each other. All position changes are essentially executed within the rotation level of the wheels. The invention also relates to the device used for implementing the method.

Description: A method of controlling fibre generation in the manufac¬ ture of mineral fibres from mineral melt with the aid of centrifugal force and an apparatus for the implementation of the method. The invention relates to a method of controlling the ge¬ neration of fibres according to the preamble of patent claim 1, and a device for the implementation of the method. The device characteristics are set out in patent claims 7 to 10. A fibre generation unit of this type intended for the generation of mineral fibres with the aid of centrifugal force normally consists of two to four fibre generation wheels each forming an entity provided with a drive axle, devices for the supply of air, cooling agent, binding agents and possible other additives. The wheels are per¬ manently installed in a stand on a movable carriage. Fibre generation takes place in such a manner that the mineral melt is conducted onto the peripheral surface of the first wheel in the fibre generation unit from which the melt is thrown in the form of a cascade of drops onto the next adjacent wheel and further onto the subsequent wheel's peripheral surface. The mineral melt fixes onto the peripheral surface of each wheel in the form of a ribbon. Fibre embryos are thrown out of this melt ribbon and are drawn into fibres with the aid of gas jets. The fibres are collected onto a receiving conveyor in the form of a fibre mat. Fibre generation is influenced by various factors. The melt viscosity affects the melt's ability to fix onto the defibrating wheel's peripheral surface and form a melt ribbon from which the fibre embryos are thrown out. There must be a suitable balance prevailing between the amount of melt fixing on the peripheral surface and the amount directly thrown further and thrown out of the melt ribbon in the form of fibre embryos respectively. The amount of mineral melt flowing down directly affects the force with which the melt hits the peripheral surface and therefore also the amount thrown further onto an ad- jacent defibrating wheel and the amount forming a ribbon of mineral melt on the peripheral surface respectively. The fall angle of the mineral melt against the receiving defibration wheel's peripheral surface is of decisive importance for the formation of the melt route from one defibration wheel to the next. The melt route in turn influences the yield of fibre from the process; i.e. the amount of fibre received as compared with the amount of mineral melt; and the mineral wool quality. The defibration wheels' rotation speed influences the thickness and length of the fibre being generated; higher speeds produce thinner fibres, while thicker fibres are always longer. In accordance with prior art technology, the defibration wheels are permanently installed in a stand within a mov¬ able carriage. Thus, the defibration unit can be placed in relation to the falling mineral melt stream so that the stream hits the receiving defibration wheel surface at a desired point. The carriage position is not adjusted while the process is in progress. It is not possible to adjust the defibration wheels' mutual positions, which means, among other things, that it is impossible to take into account changes in the drop cascade thrown from a wheel onto an adj cent wheel or influence the melt route. The purpose of this invention is, therefore, to make it possible to control the defibration wheel position within the defibration unit in relation to the continuous and/or uncontrollable changes occurring in the process, the amount and consistency of the mineral melt, mineral wool quality and/or the yield of mass from the process. The objective is reached in accordance with this inven¬ tion by providing the fibre generation method with the features defined in the characterizing part of patent claim 1. In accordance with this invention it is, thus, possible to control the position of one or more defibration wheels on the basis of impulses obtained from the factors in¬ fluencing the defibration process. The control may apply to the position.of the first receiving wheel in relation to the falling melt stream, and/or the position of one or more wheels in relation to each other. In accordance with an advantageous mode of this invention, the defibration wheels are rigidly mounted in relation to each other, but turnable as a unit around a rotation axle parallel with the defibration wheel axles. The rotation axle may be located anywhere in relation to the defibration wheels, inside or outside the space con¬ fined by their peripheries. The rotation axle is advan¬ tageously located in the line along which the melt stream hits the first receiving defibration wheel. In accordance with another advantageous method, one or more of the defibration wheels are individually control¬ lable. The controllable wheel or wheels may be shifted essentially radially while retaining their axial direc- tion and possibly slightly forwards or backwards simulta¬ neously; radially and angularly against their axial di¬ rection and possibly slightly forwards or backwards sim¬ ultaneously. The factors influencing the defibration process are the melt properties, such as its temperature and therefore the viscosity; wheel load, which primarily depends on the amount of melt stream per time unit and the size of the fall angle. The changing melt properties provide the device processor with a "feed forward" impulse and the necessary controls are executed in the defibration process. Changes occurring in the melt route, axle load, etc. in¬ fluence the fibre yield and the ready-made fibre; where- by, measurement values constituting a "feed back" impulse are compared with the pre-set default values and the necessary controls are executed in the defibration pro¬ cess. For regulating the defibration wheel's positions, prior art electronic, hydraulic or pneumatic control is used. Manual control is also possible. In accordance with an advantageous application, the con- trollable defibration wheels are provided with magnetic bearings, while bearing deviations constitute a measure of wheel load changes used for the corresponding control of fibre wheel positions to compensate the wheel load changes. By controlling the positions of the defibration wheels, it is thus possible to quickly, on the basis of both the "feed forward" and "feed back" impulses, control the pro¬ cess to change the factors affecting the defibration pro- cess and accomplish an end-product with the required pro¬ perties. The following is a description of two advantageous imple¬ mentation method types and the device in accordance with the invention with reference to appended drawing where figure 1 shows a draft of a defibration unit seen from the front and consisting of four defibration wheels, and figures 2 and 3 show how the melt route is changed in a defibration unit after the wheel position control has been executed; figure 2 shows a draft of a mainly iden¬ tical defibration unit with figure l, as seen from the front, consisting of four defibration wheels in an im¬ plementation drawn with continuous lines as well as an implementation form drawn with dashed lines showing the wheel position following the control, with the melt route drawn for the non-controlled position, and figure 3 shows using a continuous lines the figure shown with dashed lines in figure 2, with the new melt route drawn. In figure 1, the four defibration wheels are marked with 1, 2, 3 and 4. The method processor P is drawn with five contact parts, of which the one marked with 0 is in con- tact with the melt stream; the one marked with lp is in contact with defibration wheel 1, the one marked with 2p„ is in contact with defibration wheel 2, etc. The melt stream is indicated by 6, its falling point on the pe¬ ripheral surface of wheel 1 with 11, on the peripheral surface of wheel 2 with 12, on the peripheral surface of wheel 3 with 13, and on the peripheral surface of wheel 4 with 14. The drop cascade thrown out is generally marked with 15. The melt route has been marked with 16. The melt ribbon around the wheels' peripheral surface has not been drawn, while the melt ribbon section from which the drops are thrown out has been referred to in a rough draft form and has been marked with 17. In the method in accordance with figure 1, defibration wheel 3 has been moved downwards at an angle to the right as result of a control issued from the processor section 3 . The wheel in its new position drawn with dashed lines is called wheel 3 rl . The changed melt route has not been drawn. Figure 2 shows a defibration unit with four defibration wheels like the one in figure 1. In the unit, the wheels are rigidly mounted in relation to each other, but turn- able round a rotation axle drawn through point 11, paral¬ lel with the defibration wheel axles. The continuous lines show the wheel positions prior to the control, while the dashed show the new positions of the wheels. In the position before the control, the line drawn through the turning axle 11 and the centre of the wheel forms the angle ct in relation to the melt stream supplied 6, while the said line though the turning axle and the shifted centre form the angle α r , whereby the defibration unit has been turned by the size of the angle α-α-.. The melt route 16 shows the melt route between the wheels before their positions have been adjusted. Figure 3 shows the shifted defibration wheels from figure 2 with continuous lines as well as the melt route 16 r which has been shifted into the adjusted wheel position. In accordance with figure 2, the melt route is shifted in its entirety from the peripheral surface of one defibrat- ion wheel onto that of the next defibration wheel, from wheel 1 up to wheel 4. In accordance with figure 3, part of melt route 16-. is thrown with the drop cascade 15 r from the peripheral surface of wheel 2 χ onto the peripheral surface of wheel l r , while part of it is thrown directly further onto the peripheral surface of wheel 3 r . In the same manner, part of melt route 16 r is thrown back from the peripheral surface of wheel 4 r onto the peripheral surface of wheel 3 r before being transported further by gas jets and stretched into fibres collecting on a con- veyor. The following overall description of the defibration pro¬ cedure shows the advantageous aspects of, for example, the above reverting of the melt route onto the preceding. defibration wheel. Melt stream 6 hits the wheel 1 in a certain position with a certain speed. Wheel 1 is to transport the material via predropping phase and impulse transfer by means of the melt quantity and its movement speed in a rapid and most uniform drop cascade onto wheel 2. The drop cascade is to have minimal sectorial spreading; i.e. the predropping must take place rapidly. In order to achieve a rapid pre¬ dropping from the melt, the wheel 1 must cause a large angular change in the melt. In the case of successful cascade formation from wheel 1, wheel 2 is hit by a melt stream so far little dispersed, which means that the delay which causes unfavourable drop collisions still remains fairly little. The drop-formed melt stream should now fix as thoroughly as possible onto the melt ribbon on the peripheral surface of wheel 2 con¬ stituting the fibre generation surface to be subsequently thrown onto the next defibration wheel 3 in an effective manner. The higher the drop cascade's impact force against the melt ribbon, the better the fixation of drops onto it, provided that splashing is minimized. The melt ribbon consists of older melt fixed on the wheel's pe¬ ripheral surface. The melt contained in the melt ribbon is not replaced in step with the continuous flow of new melt, which means that a melt ribbon remains on the pe¬ ripheral surface. The fall angle of the drop cascade from wheel 2 onto wheel 3 is again selected in such a manner that a suit- able impact force and sectoral spreading are obtained on the peripheral surface. The drop cascade between wheel 2 and wheel 3 always has a higher speed and smaller drops than the one between wheels 1 and 2. The drop cascade from wheel 2 to wheel 3 often has a rather large sectoral spreading. This causes a great num- ber of drop collisions within the machine's transport section, which is a disadvantage. Concerning wheel 3, it is even more important for the drop cascade to have a high impact force, as the melt circle rotates faster on wheel 3 than wheel 2. The smaller, size and higher speed of the drops between wheels 2 and 3 facilitates fixation onto the ribbon. It is desirable that the melt leaves the wheel 3 in the form of fibres in great amounts. The drops in the drop cascade from wheel 3 possess a high speed and small size. A cascade hitting the wheel 4 with- in a wide sector must have minimum mobility to prevent excessive splashing. A cascade hitting wheel 4 within a wide sector must have minimum mobility in order to avoid excessive splashing. The drop cascade from the wheel 4 should be a small one, because the secondary defibration taking place after wheel 4 is uncontrollable, and the resulting fibres difficult to impregnate with binding agents. The above clearly shows that the wheels' position in re¬ lation to the melt route is of major importance for the fibre generation to take place with minimal waste and so that the result is uniform, high quality fibres. It is shown, for example, that a low melt stream position on wheel 1 results in poor fixation within the entire machine. It is therefore necessary for the melt stream to hit wheel 2 less tarigentially. This in turn makes it necessary to lift wheel 2 so as to avoid splashing. The position control of the defibration wheels can advan¬ tageously be combined with wheel rotation speed adjust¬ ments in compliance with the current fibre generation conditions. The rotation speed of individual wheel axles can also be controllable. With above arrangements, it is possible to improve the fibre generation process in such a manner that machine capacity, mass output and resulting fibre quality are optimized. In the case of manual wheel control, the empirical ap¬ proach is to be applied. By visual inspection of the melt route, specialists are able to judge whether the output is good and the wool quality high or not.

Claims: Patent claims 1. A method of controlling fibre generation in the manu¬ facture of mineral fibres from mineral melt with the aid of centrifugal force using several cooperating defibrati¬ on wheels in a defibration unit where the mineral melt flows down onto one of the defibration wheels from which the melt is thrown further onto an adjacent defibration wheel with the procedure repeated until the last defibra- tion wheel, with the embryos thrown from the defibration wheels' peripheral surfaces and drawn into fibres with aid of gas jets, characterized in that the position of one or more defibration wheels (1-4) within the defibrat¬ ion unit is adjusted essentially at the rotation level of the defibration wheels on the basis of the various fac¬ tors affecting the fibre generation process. 2. A method as claimed in patent claim 1, characterized in that all defibration wheels (1-4) are turned as a rigid entity around an axle parallel with the defibration wheel axles (11) . 3. A method as claimed in patent claim 1, characterized in that the position of one or more defibration wheels (3) is individually controlled. 4. A method as claimed in patent claim 1, characterized in that the position of the defibration wheels is con¬ trolled on the ' basis of measurements made on the melt properties; 5. A method as claimed in any of the above patent claims, characterized in that the position of the defibration wheels (1-4) is controlled on the basis of measurements made of the. wheel load. 6. A method as claimed in any of the above patent claims. characterized in that the wheel position is controlled on the basis of measurements made on the properties and/or amount of fibre. 7. A device for controlling fibre generation within a defibration unit for the manufacture of mineral fibres from mineral melt, with the unit containing at least two cooperating defibration wheels arranged, with the help of centrifugal force, to throw the mineral melt falling down on the peripheral surface of the defibration wheel fur¬ ther onto an adjacent defibration wheel, characterized by the elements for controlling the defibration wheels' po¬ sition within the defibration unit on the basis of the various factors affecting the defibration process. 8. A device as claimed in patent claim 7, characterized in that the axles of all defibration wheels are perma¬ nently installed in a stand which is turnable around an axle parallel with one of the defibration axles. (11) . 9. A device as claimed in patent claim 7, characterized in that at least one of the wheel axles is provided with an element for individual control of the defibration wheel (3) position within the defibration unit. 10. A device as claimed in any of the patent claims 7-9, characterized in that the axle of at least one of the defibration wheels is provided with magnetic bearings.

Inventors: AASTRAND ERIK AXEL, HOIKKA TIMO OLAVI, AASTRAND, ERIK, AXEL, HOIKKA, TIMO, OLAVI
Applicants: PAROC OY AB
Application year: 1991
Main classification: C03B37
IPC codes: C03B37