MXPA01002658A - System for delivering coolant air to a glass fiber attenuation zone - Google Patents

Abstract

A method and apparatus (10) for forming continuous glass fibers. The method includes the steps of supplying a plurality of streams of molten glass (16) from a bushing (14), drawing the streams (16) into continuous glass filaments (20), providing a stream of coolant air (12) parallel to the direction of draw of the streams of continuous glass filaments (20) at the front and back of the bushing (14) to entrain the coolantair (12) wherein the entrainment of the coolant air (12) is determined by the speed at which the glass filaments (20) are drawn;and then collecting the continuous filaments (20). The apparatus for delivering non-intrusive coolant air (12) to an attenuation zone of a glass drawing process of a bushing (14) including a bushing tip plate (14) having a plurality of bushing tips (18) includes at least two plenum chambers (26) having inlets (28) into which coolant air (12) is fed under pressure at a selected flow rate to discharge outlets (30), the discharge outlets (30) extend a longitudinal length of the bushing tip plate (14) to provide coolant air (12) to a front and back of the tip plate (14);wherein the entrainment of the coolant air (12) is a function of the speed at which the glass filaments (20) are drawn.

Description

SYSTEM FOR DISTRIBUTING COOLING AIR TO A GLASS FIBER ATTENUATION ZONE TECHNICAL FIELD INDUSTRIAL APPLICABILITY OF THE INVENTION This invention relates to a system for distributing cooling air to a glass fiber attenuation zone of a fiberglass mechanical stretching process. More particularly, this invention relates to a method and apparatus for distributing non-intrusive cooling air to the attenuation zone of a glass stretching process where the cooling air flow is determined by the speed at which the glass filaments are stretched. The localized vacuum created by the movement of the fiber induces the air flow at nominal speeds and allows the glass fibers to enter the cooling air when required without variation in the diameter of the fiber. The apparatus provides the supply of cooling air required at least the front and rear portions of the sleeve used to stretch the glass, and preferably around the entire periphery of the tip plate.

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BACKGROUND OF THE INVENTION The present invention relates to the formation of glass filaments and, more particularly to the apparatus and method to provide a uniform thermal environment in the attenuation zone beneath a plurality of perforated tips forming filaments on a hose that forms hot fiberglass. It is well known in the art how to produce glass fiber filaments by flowing a flow of molten material from a plurality of perforated tips provided on the bottom of a heated sleeve. The flows are attenuated, usually by mechanical means, in filaments. The filaments are gathered into strands and can then be processed into a variety of commercial products. More particularly, in the production of glass fiber strands, the molten glass flows from a suitable source towards the hot sleeve assembly. This sleeve is generally an elongated channel having side and end walls and a generally flat bottom which contains a large number of nozzles or tips through which the molten glass passes. In the area immediately below those tips, molten glass is formed into filaments. This zone is the zone of attenuation, in which the glass fibers are cooled, they can have a sizing applied to them and they are gathered in a strand. Finally, the j ^ & MMfeaiua. . -w > ^^^^^^ & amp; & ß¡¡ ^ strands are rolled onto a reel in a glass pack. The environment in the area directly below those points is crucial in the formation of the filaments because it is in this area that the molten glass cools. When the strands of the strand are cooled, their mechanical properties and physical dimensions are established. For a more detailed description of a method and / or apparatus for producing filaments reference is made to U.S. Patent Nos. 4,118,210; 3,040,377; 2,300,736; 4,018,586; 4,636,234; 4,622,054; 4,325,722; and 4,886,536, incorporated herein by reference. There are four main factors in the formation region that affect fiber formation. Those are the air, the fibers, the fins and the tip plate. The temperature distribution of the tip plate governs the production of glass at each of the tips. The glass flows by gravity through the tips and is attenuated towards the final diameters with the winder holding the tension. When the glass jets are attenuated from their initial diameter to their final diameter, they lose heat by radiation to the fins and by convection of the surrounding air. Also, the advance of the air pulls air from the surroundings towards the fiber fan. The air penetrates the fibers starting at the edge of the tip plate and works towards the middle part. During this process, there is heat exchange between the air and the fins, the air and the fibers, as well as the air and the tip of the plate. The air becomes progressively hotter towards the middle part of the tip plate. In addition, the velocity component 5 parallel to the tip plate becomes smaller (ie higher at the edge of the tip plate) when the incoming air is pulled down the fibers and is eventually "squeezed" "of the fiber fan. It is the history of attenuation (diameter, speed and temperature of the local fiber) of each of the fibers dictates the entry of air. The incoming air cools the tip plate. As a result of changing temperatures and air velocities, the heat transfer coefficient below the tip plate can be function of the local position. This implies that the air can contribute to temperature gradients of the tip plate, which in turn means variations in the flow of glass from end to end. In addition, the air influences the history of attenuation of the fiber (diameter, speed and temperature of the fiber as a function of the direction of attenuation). Since the incoming air is cooler at the periphery of the tip plate and warmer in the middle part of the tip plate with changing speeds, the air can ^^^^^^ fc?? y ^^? a ^ ft¡ * á ^^^^^^^^^^^^^^^^^^^^^ a «á? ^^ ^^^^ cool part of the fins while heating the rest of the fin. As it has been observed, the attenuation of the fiber contributes to the heat load of the fin, affects the temperature and air intake. The attenuation of the fiber is strongly influenced by the physical properties of the glass. Those physical properties include viscosity, surface tension, density, specific heat, emissivity (total hemispherical), and thermal conductivity. It will be appreciated that since the glass is an absorbing-emitting medium, the total hemispheric emissivity (which determines the radiant heat loss of the fiber) and the thermal conductivity (which determines the conduction in the fiber) depend on the data of the absorption coefficient against the wavelength. These data depend on the temperature. In addition, total hemispheric emissivity and thermal conductivity are governed by the optical thickness (distance by the coefficient of absorption) and temperature. The fins exchange radiant heat with the tip plate and the attenuation fibers. They also participate in the exchange of heat by convection and conduction with air. The location / orientation of the fin under the tip plate can be very important because the radiation exchange factors observed as well as the air flows can suffer some impact. The coefficient of heat transfer in the fin manifold influences the removal of heat from the fin and impacts the formation process. The tip plate, which determines the conditions of the glass that comes out of the tip, exchanges radiant heat with the fins and transfers heat by convection and conduction with the air. It will be appreciated that the fields of air flow and temperature can lead to different temperatures of the tip plate (from position to position). It will be appreciated that due to the fields of flow and temperature of the incoming air, each fiber experiences a different thermal environment and its history of attenuation is therefore different. This means that the initial conical angle for each fiber can be different, which, in turn, results in different glass yields because the yield, among other quantities, also depends on the initial conical angle. Fluctuations in temperature in this area will result in variations in the diameter of the strands. In addition, if the environment in the area immediately below the tip of the sleeve is supercooled, the filaments formed by the sleeve will have larger diameters and may not resist the gathering and winding forces applied to them causing the filament to break. Conversely, the filaments ^ which are subcooled may break due to their instability. Additionally, dispersed air streams can bring undesirable materials to the attenuation zone thereby breaking the filaments and decreasing the efficiency of production. The efficiency of the production is also measured by the percentage of breaking or yardage in the short term. The efficiency of the production can also be measured in terms of the reduction of the required inputs, that is, the material, energy, time, and equipment to achieve the same breaking percentage. It is also well known that forcing air in the attenuation zone, perpendicular to the flow of the fiber, can disperse the fibers in random currents compared to the ordered filaments. The random flows are then collected on a rotating drum to be used as a cut textile fiber. In an appropriately controlled environment, without forced air flow, the ordered strands can be combined into a high quality strand that can be rolled onto a reel like a glass pack. A typical use for such a strand is in the formation of glass fabrics. In order for a satisfactory woven fabric to be produced, it is imperative that the diameters of each glass strand be consistent. Variations in the diameters of the glass strands along the same result in a fabric that will not be flat but will be "wrinkled". Such a cloth is unacceptable. The problems associated with the prior art cooling apparatus include, for example, low production speed due to high breakage, inadequate distribution of the molten material to each tip, poor quality fabric due to variations in the diameter of the strand of glass, inefficiency due to high process costs, and inefficiency due to the investment of equipment high capital. Compared with the hitherto known practice of blowing cooling air to the fibers, it will be appreciated that an air curtain according to the present invention is non-intrusive and has the potential to aerodynamically isolate one position from the other. In view of the above, an object of the present invention is to provide an apparatus for producing high quality glass fiber. Another object of the present invention is to provide an apparatus for producing a glass fiber with a reduced breaking percentage. Another object is provide an apparatus for producing fiberglass of simplified design and of generally lower cost than the prior art apparatus of the same type. Still another object of the present invention is to provide an apparatus for producing fiberglass that efficiently utilizes air cooling. Still another object of the present invention is ^^^^^^^ g ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ awrt ^^^^ ^^ B ^ w ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^ provide a method for producing fiberglass using the apparatus described.

BRIEF DESCRIPTION OF THE INVENTION 5 Briefly, a method and apparatus for forming continuous glass fibers is provided herein. The method includes the steps of supplying a plurality of molten glass streams from a sleeve, stretching the continuous glass cooling flows, providing a flow of cooling air parallel to the direction of the stretching of the continuous glass filament flows in at least the front part and the rear part of the sleeve for the cooling air to enter, where the cooling air inlet is determined by the speed at which the glass filaments are stretched; and then collect the continuous filaments. The apparatus for distributing non-intrusive cooling air to a zone of attenuation of a glass drawing process of a sleeve includes a tip plate of 20 sleeve having a plurality of sleeve tips including at least two plenums having inlets. in which the cooling air is fed under pressure at a selected flow rate to the discharge outlets. The discharge outlets extend longitudinally along the tip plate of the -O. »--í ^. ^ & - -. . ' ----- ° £ < * > : & - ^ í- ^ ..? - - The" . ^ 3ft ^ w- ^ > gjj j ^ jj ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^. ^^^^^^ - ^^ ^^ cuff to provide cooling air to the front stop and rear ^ of the tip plate. The entrainment of the cooling air is a function of the speed at which the glass filaments are stretched.

BRIEF DESCRIPTION OF THE DRAWINGS The additional features and other objects and advantages will become clear from the following detailed description made with reference to the drawings, in which: FIGURE 1 is a bottom view of a sleeve including an apparatus for dispensing cooling air according to the present invention; FIGURE 2 is a cross-sectional view of the sleeve of FIGURE 1, taken along line 2-2; FIGURE 3 is a cross-sectional view of the sleeve of FIGURE 1, taken along line 2-2, which uses another apparatus for distributing cooling air in accordance with the present invention; FIGURE 4 is a cross-sectional view of the sleeve of FIGURE 1, taken along line 2-2, which utilizes another apparatus for distributing air in accordance with the present invention; and FIGURE 5 is a cross-sectional view of the sleeve of FIGURE 1, taken along line 2-2, which uses another apparatus for distributing air in accordance with the present invention.

DETAILED DESCRIPTION AND "PREFERRED DUALITIES OF THE INVENTION Referring to the figures where similar reference characters represent similar elements, there is shown a system and an apparatus 10 for distributing convective cooling air 12 to a glass fiber attenuation zone 10 of a sleeve 14. As is well known in the art, the molten glass 16 is drawn through. sleeve tips 18 through the sleeve 14. A plurality of sleeve tips 18 is placed in an array on the tip plate of the sleeve. When the molten glass 16 is attenuated through the tips of the sleeve 18, glass cones are formed. After additional attenuation, these cones are formed into filaments 20, which are subsequently gathered into composite strands. It will be appreciated that although the present invention is shown in the figures in cooperation with a single lower sleeve, the invention can also be used with an equal installation with a double lower sleeve, ie two tip plates separated by a space, of a type well known in the art. eleven eA ^ - -S "~? ^ * í ^^^ your $ fa & Bi &g > The sleeve tips 18 are typically cooled by means of a plurality of cooling fins 22 operably linked to a liquid cooled manifold 24. The cooling fins 22 are operably linked to the manifold 24, so that heat can be removed from the surrounding area of the sleeve tips 18. As shown in FIGURE 1, the fins Cooling 22 are arranged between rows of sleeve tip 18. FIGURE 1 also illustrates the connection of cooling fins 22 to manifold 24 and the direction of displacement of refrigerant fluid within manifold 24. The heat is removed through the cooling fins 22 and finally is removed by the liquid flowing in the manifold 24. As shown in the figures, the manifold 24 may be a hollow tube or the like and the cooling fins 22 may be in the form of solid fin members . In a to alternative embodiment, a second multiple 24a may be operably connected to an opposite side of the cooling fins 22 as shown in FIGURE 5. However, it will be appreciated that the exact means employed for such cooling are not important to the operation of the present invention and are well known in the art. Referring to the figures, the system and apparatus 10 include at least two plenums 26 in which a cooling gas such as COITO air is fed under pressure at a suitable flow rate. In a preferred embodiment, the cooling air is at a temperature not higher than the ambient temperature for efficient operation. However, the cooling air can be cooled when desired. The cooling air enters the plenums 26 through the inlets 28 and exits the system through the discharge outlets 30. The discharge outlets 30 extend longitudinally along the tip plate 14 on both sides of the tip plate to provide a satisfactory cooling air coverage. Discharge outlets 30 are designed to provide between 150-300 cfm (cubic feet / minute) (4245-8.49 cubic meters / minute) of wire cooling air and reinforcing type sleeves having a performance of approximately 50- 300 lbs / hr (22.68-136.08 kg / hr). However, it will be appreciated that the amount of cooling air can be adjusted as desired for the type of sleeve design employed. The openings in the discharge outlets 30 comprise less than 1% of the total surface area of the outlet. Referring to FIGURES 2-5, alternative embodiments of the apparatus for providing cooling air to the attenuation zone are shown in both the front and the back of the tip plate 14, and preferably at least preferably all the periphery of the tip plate. The plenums 26 may be rectangular in shape (FIGURES 4 and 5) or the plenums may have a "boot shape" (FIGURES 2 and 3). The plenum chambers 26 may include blades 32 for directing the cooling air flow perpendicular to the tip plate 14. The outlets 30 may be placed on top of a plane formed by the cooling fins 22 (FIGURE 4) below the plane. formed by the cooling fins (FIGURES 2, 3 and 5) or parallel to the plane formed by the cooling fins (FIGURE 5, shown in shaded line). In a preferred embodiment, the discharge outlets 30 of the plenum 26 are positioned approximately 0-4 inches (0-10.16 centimeters) from the edge horizontal of the tip plate 14 and no more than about 3 inches (7.62 centimeters) from the bottom of the tip plate. The cooling air exits from the outlets 30 substantially vertically downwards towards the attenuation zone directly adjacent to the tips 18 to form an air curtain over at least the front part and the rear part of the sleeve, preferably the entire periphery of the sleeve. A localized vacuum is created by the movement of the fiber and induces the flow of cooling air at nominal speeds and allows the glass fibers to get air from 14 Cooling when required without variation in fiber diameter. It will be appreciated that a perforated screen (not shown) can be used to reduce turbulence in the cooling gas and also acts as a filter to prevent any particulate matter from coming into contact with the glass fiber filaments being formed. It will further be appreciated that the air curtain distributes a majority of the cooling air substantially vertically downward on at least the front and back of the tip plate 14, preferably all the periphery of the plate of the tip, to allow the fibers that are being attenuated between the required amount of cooling air as dictated by the movement of the fibers. A minor component of the cooling air can also be angled in the glass fibers, so as not to disturb the attenuation zone. In comparison with the hitherto known practice of blowing cooling air to the fibers, it will be appreciated that the air curtain is non-intrusive and has the potential to aerodynamically isolate one position from the other. In addition, it has been found that providing only cooling air parallel to the flow direction of the glass fibers in and on at least both of the front and back of the tip plate 14 requires a smaller amount of cooling air. on the systems known hitherto to achieve the same cooling effect and, in addition, as an additional benefit, yardage is improved in the short term. In operation, the sleeve is supplied with molten glass, which passes through the tips 18. The fin plates 22 are properly positioned below the tip plate 14 and a liquid cooling fluid is passed through the multiple at a desired flow rate to extract heat from the fin plates. The cooling air that is introduced to the plenums 26 passes through diffuse screens and flows in a non-turbulent manner parallel to the direction of traction of the glass fibers on both sides of the tip plate. The cooling air is drawn into the attenuated area so that the filaments are attenuated in a uniform environment. The Patents and documents described herein are incorporated, therefore by reference.

Claims (10)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property.

1. A method for forming continuous glass fibers, comprising the steps of: providing a plurality of flow of molten glass from a sleeve; stretch the flows in continuous glass filaments; providing a cooling air flow parallel to the direction of stretching of the continuous glass filament flows over at least the front part and the rear part of the sleeve to introduce the cooling air where the cooling air inlet is determined by the speed at which the glass filaments are stretched; and collecting the continuous filaments,

2. The method according to claim 1, characterized in that between 150-300 cfm (cubic feet / minute) (4245-8.49 cubic meters / minute) of cooling air are provided.

3. The method according to claim 1, characterized in that the flow of cooling air is substantially vertical downward.

4. The method according to claim 1, characterized in that the cooling air flow is at room temperature. The method according to claim 1, characterized in that the cooling air flow is provided parallel to the direction of stretching of the continuous glass filament flows over the entire periphery of the sleeve on at least the front and rear of the sleeve. 6. The apparatus for distributing non-intrusive cooling air, to an attenuation zone of a glass stretching process of a sleeve, including a sleeve tip plate having a plurality of sleeve tips, the apparatus is characterized in that comprising: at least two plenums including inlets in which the cooling air is fed under pressure at a selected flow rate for discharge outlets, the discharge outlets extend longitudinally along the sleeve tip plate to provide cooling air to the front and back of the tip plate; where the entrance ? ^^^^^^^^ to ^^^^^^^^^ cooling air is - um ^ lon speed at which the glass filaments are stretched. 7. The apparatus according to claim 6, wherein the discharge ports are disposed above a plane formed by cooling fins secured beneath the plate of the tip of the sleeve. 8. The apparatus according to claim 6, wherein the discharge ports are positioned below a plane formed by cooling fins secured beneath the plate of the tip of the sleeve. 9. The apparatus according to claim 6, wherein the discharge ports are arranged parallel to a plane formed by the cooling fins secured beneath the plate of the tip of the sleeve. The apparatus according to claim 6, characterized in that the cooling air exits the discharge outlets substantially vertically downwards, directly adjacent to the tips to form an air curtain in the front and rear of the sleeve.