CONVEYOR SCALE FOR CONTROLLING ROCK WOOL SURFACE DENSITY

Abstract: The object of the present invention are rock wool process conveyor scales for controlling and adjusting the specific surface density of the rock wool in rock wool production. The rock wool process conveyor scales are based upon the measurement of the rock wool mass flux. The entire conveyor belt (2) construction together with the driving motor (3) is suspended from mobile levers (4), part of the gravitational force of the conveyor belt (2) and the driving electric motor (3) being intercepted by the dynamometers (5), and the remaining part being counterbalanced by the weights (7) via the levers (6). The ratio of the masses of the freely suspended conveyor belt (2) and of the motor (3) to the weights (7) is selected in such a manner that the dynamometers (5) intercept principally the net weight of the rock wool layer (1) present on the conveyor belt (2).

Description: CONVEYOR SCALE FOR CONTROLLING ROCK WOOL SURFACE DENSITY The object of the present invention are rock wool process conveyor scales for controlling and adjusting the specific surface density of the rock wool in rock wool production. In rock wool production, the surface weight or the specific surface density of the final product is one of the paramount parameters involved in the process, allowing the product to achieve the highest quality level. The said parameter directly depends on the time variation of the rock wool mass flux on the production line. The mass flux variation depends on various multivariable parameters which are generally random in character. By certain interventions at the spot where the melt is being generated and scattered into fibers (dome furnace/centrifuge), the intensity of the time variation of the rock wool mass flux may be diminished, although it can never be completely eliminated. For this reason, nowadays in practical applications a regulation method is generally employed, which, by varying the velocity of the conveyor belts and of the roller/conveyor systems along the production line, guarantees a constant surface density to the final product. By increasing or decreasing the velocity of the line, the instantaneous deviation of the rock wool mass flux from the nominal mass flux, a defined technological datum for a given product, can be regulated. Nowadays, the problem described above is generally solved by means of double regulation, comprising the primary and secondary conveyor scales and the corresponding regulation signals. The quality of both signals has a direct influence on the quality of the regulation. Usually, the primary scales signal measures the base dynamics of the process and is periodically adjusted by means of the secondary scales signal, the average value of the l tter being more reliable over longer periods of time. With the prior art technical solutions, the primary conveyor scales commonly measure the mass flux by measuring the reaction force of the conveyor belt acting on the force measuring sensors, which is usually done through the use of a pair of sensors. These sensors, however, do not directly measure the gravitational force of the rock wool layer moving along the conveyor belt, they only measure the multiparametric proportional functional interdependence of the instantaneous rock wool mass flux and the instantaneous reaction force applied to the embedded sensors. The paramount interfering quantities influencing the measured signal of the rock wool layer gravitational force are the varying tension force in the belt, due to the temperature dilatation, and the varying force related to the mechanical properties of the belt itself. These phenomena have a negative effect upon the reliability of the measuring results in prior art scales. The object of the invention is to devise and construct rock wool process conveyor scales which will be not only more reliable and more precise than prior art scales, but first of all more independent of the said interference factors which have a negative effect upon the accuracy of the measurements. According to the invention, this object is achieved by the independent patent claims. The present patent application discloses the modified concept of measuring the rock wool mass flux on the primary scales. The rock wool mass flux is defined by the measured velocity of the conveyor belt 1. e. of the rock wool layer (measured m m/s) and by the net gravitational force of the length unit of the rock wool layer which, at a given moment in time, is present on the scales m (in kg/m) . m = v x m 1 (kg/s) The net weight of the rock wool layer is measured after having counterbalanced the entire conveyor belt construction via four crank mechanisms with weights, selected on the basis of the balance of the forces in their points of application. The invention shall be described with reference to an embodiment thereof, illustrated by a drawing . Fig. 1 a schematic view of the rock wool scales The rock wool layer 1 travels jointly with the conveyor belt 2. The velocity of the conveyor belt 2 and the velocity of the rock wool layer 1 are equal. The velocity of the conveyor belt 2 is measured in terπto of frequency of the continuous frequency regulator of the driving motor 3. The entire conveyor belt 2 construction, together with the driving motor 3, is suspended from mobile levers 4. Part of the gravitational force of the conveyor belt 2 and of the driving electric motor 3 is intercepted by the dynamometers 5, while the remaining part is counterbalanced with the weights 7 via the levers 6. The ratio of the masses of the freely suspended conveyor belt 2 and the motor 3 to the weights 7 is selected in such a manner that the measuring range of the dynamometers 5 is used over the whole measuring range, which is of the same order of magnitude as the gravitational force of the rock wool layer 1. Thus the stress is relieved off the dynamometers 5, which principally intercept the net weight of the rock wool layer 1 on the conveyor belt 2. The tare of the primary scales is intercepted by the weights 7 via the levers 6. The weights 7 are selected m such a way that in the stress-relieved state, when there is no rock wool layer 1 on the conveyor belt 2, the corresponding dynamometers 5 are loaded with the force »F tare«, amounting to ca. 10 of the nominal force of the dynamometer 5 »F nomιnal«. Thus, during operation, a stabile state of the conveyor belt 2 is achieved. To prevent dynamic excitation of the entire primary scales construction m operation, contactless pneumatic dampers 8 are provided which reduce mechanical vibrations of the entire system both inside and outside its resonance range. Of course, within the scope of the invention, by making use of convenient supplemental levers and/or a convenient construction, rock wool process scales, using fewer than four levers 4, dynamometers 5, levers 6, and/or weights 7, may be constructed. The above-described scales for measuring the gravitational force in four resting points permit direct measuring of the gravitational force of the rock wool layer on the moving belt, whilst compensating the mass of the conveyor belt itself. The signal of the dynamometers 5 is composed mainly of the instantaneous gravitational force of the rock wool layer 1, present on the moving conveyor belt 2, and only in a small degree of the mass of the conveying system as such, which constitutes the preload of the inventive scales. By measuring the gravitational force in four resting points according to the invention, direct measuring of the gravitational force of the rock wool layer on the moving conveyor belt, through compensating the mass of the conveyor belt itself, is achieved. This results m an increased sensitivity of the sensors and m a reduced measuring error in the measurement of the instantaneous gravitational force of the rock wool layer.

Claims: PATENT CLAIMS 1. Rock wool process conveyor scales for controlling and adjusting the specific surface density of the rock wool in rock wool production, based upon the measuring of the rock wool mass flux and characterized in that the entire conveyor belt (2) construction together with the driving motor (3) is suspended from mobile levers (4), part of the gravitational force of the conveyor belt (2) and the driving electric motor (3) being intercepted by the dynamometers (5), and the remaining part being counterbalanced by the weights (7) via the levers (6). 2. Rock wool process conveyor scales according to Claim 1, characterized in that the ratio of the masses of the freely suspended conveyor belt (2) and of the motor (3) to the weights (7) is selected in such a manner that the dynamometers (5) intercept principally the net weight of the rock wool layer (1) present on the conveyor belt (2) .

Inventors: BRADESKO FRANC, MIHOVEC BOJAN, MOZINA PETER, SIROK BRANE, &SCARON, BRADE&SCARON, MIHOVEC, BOJAN, MO&ZCARON
Applicants: TERMO D D IND TERMICNIH IZOLAC, TERMO D.D., INDUSTRIJA TERMI&CCARON
Application year: 2000
Main classification: G01G11
IPC codes: G01G1, G01G11