US3446610A - Apparatus for the continuous production of a mat of glass filaments - Google Patents

Description

May27,1969 J.'RIEDEL.

APPARATUS FOR THE CONTINUOUS PRODUCTION OF 'A MAT OF GLASS FILAMENTS Filed Oct. 23. 1965 United States Patent APPARATUS FOR THE CONTINUOUS PRODUC- TION OF A MAT OF GLASS FILAMENTS Johannchristoph Riedel, Wagrain, Salzburg, Austria Filed Oct. 23, 1965, Ser. No. 503,143 Claims priority, application Italy, Dec. 12, 1964,

Int. Cl. C03b 37/04 U.S. Cl. 659 4 Claims ABSTRACT OF THE DISCLOSURE drum.

This invention relates to a process and an apparatus for the continuous production of webs, fleeces, mats and the like, and particularly those of fiber glass.

A number of different procedures have been suggested for spinning thermoplastic materials, particularly glass, and for the subsequent immediate conversion of the threads thus obtained into webs, fleeces, mats and the like. These known procedures are essentially based on the obtention of filaments by drawing them with the aid of a rotating drum, either starting from the tips, heated at the spinning temperature, of prefabricated spinning rods, or also from a melted mass bath by means of suitable nozzles, winding the filaments over a drum and removing them therefrom, at preselected time intervals, by arresting the drum or removing the filaments, before they are wholly wound about the drum, with the help of suitable mechanical or pneumatic means so as to transfer them onto a movable supporting member whereon the web, fleece or the like may be formed. The filaments, as removed from the drawing drum before having been wound completely, arrive on the movable supporting member after having been airborne along a certain path by the airstream induced by the rotation of the drum, whereafter they are drawn by suitable sucking means onto a movable supporting member in the form of a sieve, which can be, for example, a belt or a drum. In the point where the suction becomes ineffective, it is possible to remove the web, fleece or mat, possibly after having applied beforehand a binding agent which latter could be applied, for example, by spraying.

In the case in which one starts from a melted mass and spinning is carried out by drawing from nozzles, it is known to allow the melted mass to be discharged, under the pressure of the overlying hydrostatic head, through cold outlet channels which project from the bottom of the melting pot, the thusly extruded rods being sent to an area which immediately underlies the channels in which the spinning temperature is maintained. In this case, and also in the case of spinning from prefabricated rods, there is the advantage that, even if a filament is broken for any reason, the spinning process is automatically restored in that, in correspondence with the tip of the relevant rod placed in the spinning environment, a drop is formed which, by falling, restores after a very short while, a new filament which adheres to the rotating drum to be spun thereby.

The extrusion velocity through nozzles is a function of the hydraulic head of the melted liquid mass in the melting pot, which mass is maintained at a constant level See and at the melting point, the throughput of such a process being capable of attaining 50 meters of filament a second for each spinning station.

When spinning from prefabricated rods, the maximum spinning velocity is lower, in that the rods arrive in a relatively cold condition at the spinning area, wherein they must be heated to the necessary temperature, that which takes a certain period of time.

While in the latter case it would appear impractical to increase the drawing speed of the filament to values over 40-50 meters per second, such an increase would be obtainable in the technique of spinning from nozzles since the mass coming out of the nozzles is already in a thermo-viscous condition, and the subsequent heating tllifireof to the spinning temperature is very rapidly attaina e.

However, even in the case of spinning by drawing from nozzles with the assistance of a rotary drum, a spinning speed greatly in excess of 50 meters per second has not been obtained hitherto. As a matter of fact, in order that the necessary draw be obtained for the filaments, it has been deemed essential that they should adhere to the peripehry of the rotary drum along a relatively wide are (about three quarters of the periphery). On the other hand, the higher the peripheral velocity of the drum, the stronger is the centrifugal force acting upon the filaments at the drums periphery, and the more difficult is the maintenance of the filaments to the drum by adherence. By means of suitable bafiles or guiding aprons of sheet metal, positioned at a certain distance from the drums periphery, it has been attempted to guide the drum-induced airstream while retaining the filaments adherent to the periphery of said drum but, in spite of these expedients the limited output velocities indicated above have not been substantially exceeded.

An object of the present invention is to simplify to a significant degree the conventional procedures, and to obtain a substantial increase of throughput in an installation capable of producing in a continuous and wholly automatic manner webs, fleeces, mats and the like ready for use starting from the raw material.

The principal and basic concept of this invention is the fact that, contrary to the teachings of the contemporary art, it has been now surprisingly ascertained that, in order to obtain an adequate drawing action for the filaments from the spinning stations, it is not quite necessary that said filaments should adhere to the periphery of the rotary drum along a substantial arc of the periphery thereof, it being conversely enough to provide a short and very limited contact, for example a wrap angle of In the light of this new knowledge, it has been ascertained that it is no longer necessary to counteract the pull of the centrifugal forces to which the drum-contacting filaments are subjected, but, rather, it has been provided to encourage said action so as to cause said filaments to the automatically separated from the drum after having been in contact therewith along a short are only. As a matter of fact it has been possible to make sure that the centrifugal force as such, which separates the filaments from the drums periphery, exerts on said filaments just the pull which is necessary for inducing the drawing force necessary for spinning.

The continuous production of webs, fleeces, mats and the like, made of filaments and particularly of glass filaments, is then substantially characterized according to the invention in that filaments spun from nozzles are drawn and accelerated by a drum which is rotated at such a peripheral velocity that the filaments, after a short are of contact with the periphery of said drum, due to the centrifugal force to which they are subjected, are automatically removed from said drum and, while being freely airborne by the airstream induced by the rotation of the drum, are conveyed by said stream in a quiescent space or enclosure wherein they fall due to their own weight on the bottom of said enclosure so as to form an even and homogeneous layer of the desired thickness for a web, a fleece, a mat or the like.

This arrangement according to the invention affords a number of advantages over the prior art.

In the first place, it becomes possible to have a substantial increase in the throughput by fully exploiting the production capacity of the nozzle spinning method in that the centrifugal force is utilized according to the invention for inducing the automatic separation of the filaments from the rotary drum, and such force is present to a greater degree, the higher the rotation velocity of the drum.

Moreover, all the mechanical and pneumatic means which were necessary in the prior art for detaching the filaments from the drum and collecting them on a movable supporting member so as to form a web, fleece or the like, can be dispensed with. The web, fleece, or mat obtained thereby is perfectly uniform and homogeneous even if the thickness is significant, since the formation of the deposited layer is unaffected by sucking means. The arrangement of the invention does away with any kind of movable supporting and transfer member since, on account of its high degree of homogeneity, the web, the fleece or the like forms a perfectly self-supporting structure which can be withdrawn without any supporting member whatsoever. The necessity is thus also dispensed with a means for removing the web, fleece or the like from the transfer member, this operation being necessary in the conventional routine and involving the risk of easily damaging the filaments, particularly in the case of thin and frail webs.

The self-supporting structure thus obtained can undergo, during its travel towards the point of collection of the finished product, a sizing treatment, for example by causing it to pass through a bath of a suitable sizing agent, or the like, adapted to impart to the product the final body and stiffness for the subsequent practical use.

The absolute homogeneity attained by causing the filaments to settle is ensured, according to the invention, by a phenomenon to be described hereinafter and which is advantageously exploited by adopting appropriate means.

As is known, glass filaments are charged with positive static charges by friction during spinning. This positive static charge of the filaments is not transferred to the drawing drum, the latter being grounded according to the invention or negatively charged with static electricity. As a matter of fact, it has been observed that the filaments, as they leave the drum, still possess a static positive charge having a magnitude greater than that of the charge of the filaments oncoming to the drum. Owing to the fact that the filaments, as they leave the drum, strongly flutter as they are being airborne, they become further charged by frictional static positive charges.

This phenomenon is exploited according to the invention by charging the walls of the space or enclosure wherein the filaments are collected in the form of a deposited layer with positive static electricity. For example, these walls can be made of glass, in which case said walls and the enclosure confined thereby assume the static positive charge of the oncoming filaments so that the filaments driven from said walls and, on account of their static charge, fall at equal spacings on the bottom of said enclosure. Should this bottom be arranged with a slight slope and downwardly converging towards an outlet, one obtains that the web, fleece or the like as formed within such an enclosure as the filaments are being evenly deposited therein, comes out of the enclosure continuously and spontaneously without resorting to any entraining or transfer means and in the form of a selfsupporting structure which can then be passed on for subsequent treatment. It is apparent that by so varying the slope of the bottom, it is possible to obtain structures of various thickness. The ensuing treatment which the Web, fleece, mat or the like may undergo upon leaving the enclosure in which it has been formed may consist, for instance, of an impregnation with suitable sizing agents followed by drying, eventually to supply still in a continuous form, the finished product ready for use. The product as it comes out of the drying chamber can have its edges trimmed and then be wound on reels ready for shipping.

To the electrostatically controlled chamber or enclosure wherein the Web, fleece or similar article is formed, filaments can be fed which come from a plurality of spinning devices, and homogeneous mixed structures devoid of any Stratification can be thus obtained with a corresponding increase of throughput. The invention relates also to a device adapted to put the inventive process into practice for the continuous production of webs, fleeces, mats and the like. Said device essentially comprises a melting pot with a plurality of aligned nozzles for the discharge of melted mass towards a spinning station proper wherein, with suitable heating means, the spinning temperature is maintained, after which the filaments thus obtained are passed to a takeup drum so as to form a web, fleece, mat or the like, and is characterized in that said drum is rotated at a peripheral speed such as to induce the detachment of the filaments by the action of the centrifugal force only, guiding means being also provided for guiding the filaments separated from the drum and freely airborne by the airstream induced by the rotation of the drum, towards an enclosure which is substantially confined and fitted with a fiat bottom surface for depositing the filaments introduced therein, and with an outlet opening for the finished web, fleece, mat or the like. This bottom flat surface is, with advantage, sloped towards said outlet opening.

The sidewalls and the flat bottom of the filamentcollecting enclosure are preferably made of glass or they are insulated from the ground and electrostatically charged with a positive charge, while the drum is grounded or electrostatically charged with a negative charge. The peripheral speed of the drum is greater and, advantageously, much greater than 50 meters per second and the guiding means, partially arranged around the drum, is spaced from the peripheral surface thereof, a distance such as not to impede or obstruct the separation of the filaments by centrifugal force. The purpose of the guiding means is thus only to direct the airstream generated by the rotation of the drum with the filaments airborne thereby towards the collecting enclosure which is advantageously situated at a level which is higher than that of a horizontal plane passing through the drums axis. A value of the distance between the drums periphery and the guiding means (formed, for instance, by sheet metal aprons or the like) which has proven very satisfactory is 2 centimeters.

The guiding means have an opening in quite conventional manner, disposed almost vertically beneath the drum axis, for the passage of drops falling from the spinning stations and which entrain the filaments. On account of the difference in weight between said drops and the filaments, the former are ejected by centrifugal force through said opening of the guiding means, thus coming out of the spinning device, whereas the filaments, even being detached from the drums periphery also by centrifugal force, remain in the space between said drum and said guiding means and are guided towards the collecting enclosure to formtherein the deposit in the form of a web, fleece or the like.

In order that the invention may be better understood, an exemplary embodiment will be described in the following text, without limitation, of an apparatus adapted to the production of Webs, flleeces, mats and the like of fiber glass according to the basic concepts of the invention, reference being had to the accompanying drawing whose single figure is illustrative, in a quite diagrammatical and simplified showing, of said apparatus.

Broadly stated, the apparatus comprises, as a whole, the following individual units:

(A) a spinning station A,

(B) a chamber for collecting the filaments and forming the web, fileece or the like, indicated by B,

(C) a sizing device, C

(D) a dryer, D

(E) and a collection device for the finished product,

indicated by E.

The spinning device A is of a kind known per se and is adapted to the continuous and fully automatic production of glass filaments. It comprises a trough-shaped container '1 in which a constant head of molten glass 2, is maintained. From the underside of the trough 1 project a plurality of tubular members 3, slightly cooled with means (not shown), with respect to the temperatures of the molten glass 2: the latter passes through said members 3 from the trough 1 to form small glass rods 4. These rods 4, immediately as they leave the members 3, enter a region heated by the heating means 5, wherein they form spinning stations 6. The trough 1 and the spinning region are assembled in a single body 7 of a heat insulating material.

Beneath the body 7 is arranged, on suitable journals, 8, a drum 9 which is driven in rotation about its own axis in counterclockwise direction, by a prime mover (not shown). The vertical plane along which the individual filaments 10 coming out of the spinning stations 6 is virtually tangent to the drum 9.

In its lower region, the drum 9 is surrounded, in somewhat spaced relation, by guiding sheet metal a'prons '11 and 12 which define a free interstice 13 between them. The apron 11 is hinged at 11a and can be rotated for adjustment about this point.

The collecting enclosure of chamber B consists of a bottom plate 14 and a set of walls 15, 16, 17 and 18 supported by a framing 19. The bottom has a first region which is substantially horizontal, a subsequent inclined region and a further substantially horizontal region. The slope of the intermediate region can be made adjustable by means not shown. The wall 15 is terminated at its lower edge in close vicinity to the periphery of the drum 9, and the wall elements 16, 17 and 18 which confine the upper region of the collecting chamber can be individually adjusted as to their slope by suspension members such as ropes 20 or the like. More or less wide slots are left between said wall elements.

The sizing device C comprises a tub 21 containing the sizing bath and an idler roller 22 which is partially im mersed in the bath.

The drying unit D is formed by a chamber 23 on the top of which there are a set of heating elements 24 and a blower 25 which produce a flow of hot air within said chamber. A set of guiding rollers 26, 27, a few of which are driven by a reduction gear 28 to rotate at a suitable speed, serve to guide the webs, fleece or the like, 29, from an input point 30 to an outlet point 31 of the chamber 23'.

The sized and dried web, fleece or mat, coming out of the drying unit, can be edge-trimmed with means (not shown) and then then taken up by the device E comprising a takeup drum 32 and a reduction gear 33 driving said drum.

The operation of the apparatus is as follows.

The drops falling from the spinning station 6 tangentially contact the periphery of the drum 9 which is rotated at high speed (at least 50 meters per second and preferably much more than that) in a counter-clockwise direction. As the drops contact the rotating drum, the drops receive a first acceleration momentum and are defiected from their vertical path. The drops thus swing between the drums periphery and the guiding apron 11 and at each new contact with the drum they become further accelerated along with the filaments entrained thereby. The filaments then adhere to the drums periphery and undergo a strong pull. While the drops, which have a certain weight are ejected out of the device through the gap 13 between the aprons 11 and 12, the filaments 10 also undergo the centrifugal efiect and leave the drums periphery approximately at a point lying on a vertical plane containing the axis of said drum. However, the filaments 10, as they leave the drum 9, enter the space confined by the drums periphery and the guiding apron 12 and are energetically airborne by the airstream induced by the rapid rotation of said drum.

, The fluttering of the filaments is determined and governed 'by their own acquired speed and by the guiding apron 12 which is positioned at a distance of about 2 cm. from the drums periphery. Said apron has thus the important task, according to the invention, of governing the fluttering of the airborne filaments without compelling the same to adhere to the periphery of the drum, and of guiding the filaments toward the chamber B. The drawing schematically shows the path travelled by thefilaments.

The drum 9 is electrically connected to ground or an electrostatic negative charge is imparted thereto by means not shown herein. The glass filaments 10 receive, owing to friction, a first positive static charge at the spinning stations and, due to their vigorous fluttering as they leave the drum, they are charged more intensely with positive static electricity.

The walls of the chamber B are advantageously formed by glass plates and are positively charged. There is, therefore, an electrostatically controlled space into which the glass filaments pass, the filaments themselves also having a positive electrostatic charge. On account of this expedient, the glass filaments cannot adhere to the walls of the chamber B and, in addition, since the individual filaments are each endowed with an equal static positive charge, they remain spaced at equal distances apart from each other and in such a condition they fall onto the bottom plate 14 of the chamber B forming a perfectly homogeneous and even layer thereon. Such deposited layer, on account of its homogeneous texture, is self-supporting and, according to its own thickness, it takes the form of a web, a fleece or a mat.

The self-supporting filament layer glides over the inclined bottom plate 14 of the chamber towards the outlet withoutany entraining means and then its electrostatic charge is dissipated in the atmosphere. It is apparent that the thickness of the product obtained is a function of the slope of the bottom plate 14.

The thusly formed web, fleece or mat is then passed through the sizing device C, wherein it is sized, then it enters the drying unit D wherein it is dried and, after possible trimming of its edges, it is taken up over the drum 3-2 in the form of a finished product. It is clear that the length of the path through the drying unit must be selected, optionally, longer than diagrammatically shown in the drawing.

To ensure that the start of the production may take place automatically, it is possible to provide lateral ropes or chains arranged in a closed loop configuration for driving the driven rollers 26 in the drying unit D and which extend, by means of suitable transmission means (not shown) into the interior of the chamber B. These ropes or chains, suitably connected to ground, cause the filaments introduced in the chamber B and forming the layer deposited onto the sloping bottom plate thereof, to stick to the edges of the strip of web, fleece, or mat and to said chains or ropes, the latter then driving the product through the sizing bath and the drying unit. By means of a suitable severing device (not shown) the edges with the ropes or chains are then separated from the strip of finished product.

The chamber B can be fed with filaments coming from a number of spinning stations so as to form a homogeneous, mixed and non stratified deposit. In this case, by adopting a single collecting chamber, a single sizing device and a single drying unit, it is possible to multiply the installations throughput.

The invention has been disclosed by way of example and indication only in connection with a possible embodiment thereof.

It is to be understood, however, that the invention should not be regarded as being limited to this particular embodiment, a number of variations being possible within the scope of the present invention.

Thus, for example, another spinning device could be adopted, even through the one shown and described (and known per se) has proven to be particularly advantageous, above all due to the fact that it lends itself to providing the possibility of high speed spinning. Also the subsequent treatments of the web, fleece, mat or similar product according to the invention can be other than those described herein.

I claim:

1. Apparatus for the production of a mat of glass filaments, said apparatus comprising means for extruding glass filaments from a molten mass, a rotatable drum positioned adjacent said extruding means for tangentially receiving the filaments therefrom, means for electrically charging said drum, means for rotating the drum at a relatively high speed to cause advance of the filaments with the drum over a small arc of contact thereof, and subsequent release of the filaments solely by centrifugal force whereupon the filaments are carried in the airstream generated by the rotation of the drum, 2. guide element spaced from said drum in the region beyond said arc of contact of the filament with said drum, said guide element being curved and partially surrounding the drum at the lowermost portion thereof at a distance which is sufiicient to permit separation of the filaments from the drum under the action of the centrifugal force, a chamber adjacent said drum for receiving the filaments separated therefrom, said chamber including a mat-forming floor on which the filaments are deposited, and enclosing walls, and means for applying to said walls and floor an electrical charge opposite the charge on the drum.

2. Apparatus as claimed in claim 1 wherein said electrical charge in the chamber and on the filaments is a positive electrical charge.

3. Apparatus as claimed in claim 2 wherein the drum has a negative electrical charge.

4. Apparatus as claimed in claim 1 wherein said floor and walls are constituted of glass and are positively electrically charged.

References Cited UNITED STATES PATENTS 2,586,774 2/ 1952 Bastain et al. -9 2,838,879 6/1958 Schuller 65-10 2,920,699 1/1960 sittel 65-9 X 2,987,761 6/ 1961 Schuller et al 65-9 X DONALL H. SYLVESTER, Primary Examiner.

R. L. LINDSAY, Assistant Examiner.

U.S. Cl. X.R.

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