PROCESS AND APPARATUS FOR PRODUCING STREAMS OF MOLTEN GLASS

Abstract: An apparatus (10) is provided for supplying streams of molten glass to be drawn into continuous glass fibers. The apparatus comprises a receptacle (22), a feeding device (30), a heating device (24) and a plurality of bushings (50). The receptacle (22) is adapted to receive glass-forming batch materials (40) to be melted into molten glass material (42) such that a pool (42a) of molten glass material (42) is provided in the receptacle (22) below a layer (40a) of glass-forming batch materials (40). The receptacle (22) includes a plurality of openings (70) through which primary streams (42b) of molten glass material flow. The feeding device feeds the glass-forming batch materials to the receptacle. The heating device is associated with the receptacle and is adapted to generate heat to melt the glass-forming batch materials. The bushings are located adjacent to the receptacle such that each of the bushings receives one of the primary streams of molten glass material. The bushings include a plurality of nozzles (53) for supplying secondary streams of molten glass material to be drawn into continuous glass fibers.

Description: PROCESS AND APPARATUS FOR PRODUCING STREAMS OF MOLTEN GLASS TECHNICAL FIELD This invention relates generally to apparatuses for producing streams of molten glass to be drawn into continuous glass fibers and, more particularly, to such an apparatus having one or more bushings positioned directly below a glass melter. BACKGROUND Apparatuses used to form continuous glass fibers are known in the art. Typically, such an apparatus comprises a melter, a forehearth, and a channel interconnecting the forehearth with the melter. One or more bushings are positioned below the forehearth. Molten glass material travels from the melter to the forehearth via the channel. The glass material then flows through orifices in the forehearth to the bushings. The bushings have a plurality of nozzles or tips, typically 1000 or more, through which streams of glass flow. Winders or other pulling devices are provided below the bushings for attenuating the streams into continuous glass fibers. The temperature of the glass within the bushing must be sufficiently high such that the glass is in a fluid state. However, it must not be so high that it prevents the glass, after passing through the bushing tips, from cooling and becoming viscous enough for fiber forming. Thus, the glass must be quickly cooled or quenched after it flows from the bushing tips for glass fibers to be formed. In order for quenching of the glass to occur in a timely manner, the glass delivered to the bushing should be at a temperature which is less than the temperature required to effect melting of the initial glass- forming batch materials. Forehearths and channels have been used in the past to allow the glass materials to cool before being delivered to the bushings. They also function to allow the glass materials to become homogeneous as conventional mechanical batch material mixers typically perform inadequately when used to mix the batch materials before they are delivered to the melter. Forehearths and channels, however, add significant expense to the fiber forming process. Such structures require plant floor space, are constructed from costly refractory materials, and must be heated to maintain the glass material molten. There is a need for an improved apparatus for forming continuous glass fibers such that floor space, material and energy requirements are minimized. DISCLOSURE OF INVENTION This need is met by the apparatus of the present invention wherein a melter is provided having one or more bushings positioned directly below it. Initial glass-forming batch materials are delivered to the melter where they are reduced to a molten condition and delivered directly to the one or more bushings. No delivery structure, e.g., forehearths or delivery channels, are provided. In accordance with a first aspect of the present invention, an apparatus is provided for supplying streams of molten glass to be drawn into continuous glass fibers. The apparatus comprises a receptacle, a feeding device, a heating device and a plurality of bushings. The receptacle is adapted to receive glass-forming batch materials to be melted into molten glass material such that a pool of molten glass material is provided in the receptacle below a layer of glass-forming batch materials. The receptacle includes a plurality of openings through which primary streams of molten glass material flow. The feeding device feeds the glass-forming batch materials to the receptacle. The heating device is associated with the receptacle and is adapted to generate heat to melt the glass- forming batch materials. The bushings are located adjacent to the receptacle such that each of the bushings receives one of the primary streams of molten glass material. The bushings include a plurality of nozzles for supplying secondary streams of molten glass material to be drawn into continuous glass fibers. The apparatus may further include a plurality of receiving blocks, each located between the receptacle and one of the bushings. The receptacle has a length, width and height. In a first embodiment, the receptacle includes two or more rows of openings spaced a given distance from one another along the length of the receptacle, with each row including at least two adjacent openings. For example, the receptacle may include seven rows of openings spaced apart from one another along the length of the receptacle, with each row having six adjacent openings. In a second embodiment, the receptacle includes first and second rows of openings spaced from one another along the width of the receptacle. The openings defining the first row may be positioned such that they do not share a common axis which is orthogonal to a longitudinal axis of the receptacle with any one of the openings defining the second row. Preferably, the feeding device comprises a screw-metering device which delivers glass-forming materials to the receptacle in a generally uniform manner. The heating device is preferably positioned over the receptacle such that it extends down through the layer of glass-forming batch materials and into the pool of molten glass material. It comprises at least one set of heating electrodes of opposite polarity and, preferably, a plurality of sets of heating electrodes spaced apart from one another along the length of the receptacle. Each of the bushings preferably includes approximately 400 nozzles or less and, most preferably, 200 nozzles or less. In accordance with a second aspect of the present invention, an apparatus is provided for supplying streams of molten glass to be drawn into continuous glass fibers. The apparatus comprises a receptacle, a feeding device, a heating device and at least one bushing. The receptacle is adapted to receive glass-forming batch materials to be melted into molten glass material such that a pool of molten glass material is provided in the receptacle below a layer of glass-forming batch materials. The receptacle includes at least one opening through which a primary stream of molten glass material flows from the receptacle. The feeding device is adapted to feed the glass-forming batch materials to the receptacle. The heating device is associated with the receptacle and generates heat to melt the glass-forming batch materials. The heating device is positioned over the receptacle. It extends down through the layer of glass-forming batch materials and into the pool of molten glass material. The bushing is located adjacent to the receptacle such that the bushing receives the primary stream of molten glass material passing through the opening in the receptacle. The bushing includes a plurality of nozzles for supplying secondary streams of molten glass material to be drawn into continuous fibers. In accordance with a third aspect of the present invention, a method is provided for supplying streams of molten glass to be drawn into continuous glass fibers. The method comprises the steps of: blending glass-forming batch materials such that the batch materials are substantially homogeneous; feeding the homogeneous batch materials to a melter; supplying heat to the melter to effect melting of the batch materials into molten glass material; supplying a stream of molten glass material from the melter directly to a bushing assembly; and, supplying from the bushing assembly a plurality of secondary streams of molten glass material to be drawn into continuous fibers. The bushing assembly may comprise a bushing device provided directly adjacent to the melter. Alternatively, the bushing assembly may comprise a bushing device and a receiving block. Preferably, the blending step comprises the steps of providing a pneumatic mixer and blending the glass-forming batch materials using the pneumatic mixer. Accordingly, it is an object of the present invention to provide an apparatus for supplying streams of molten glass to be drawn into continuous glass fibers comprising a melter and a plurality of bushings provided directly below the melter. It is another object of the present invention to provide a method for supplying streams of molten glass to be drawn into continuous glass fibers comprising the steps of feeding homogeneous batch materials to a melter, supplying energy to the melter to effect melting of the batch materials and supplying a stream of the molten glass material directly to a bushing located adjacent to the melter. These and other objects of the present invention will be apparent from the following description, the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a cross-sectional view through a melter constructed in accordance with a first embodiment of the present invention and showing schematically a screw- metering feed device forming part of the present invention; Fig. 2 is a side view showing the melter in cross section and showing schematically the pneumatic mixer forming part of the present invention; Fig. 3 is a view taken along view line 3-3 in Fig. 2; Fig. 4 is an enlarged cross-sectional view of a bushing assembly; Fig. 5 is a cross-sectional view through a melter constructed in accordance with a second embodiment of the present invention; Fig. 6 is a side view showing the melter of Fig. 5 in cross section; Fig. 7 is a view taken along view line 7-7 in Fig. 6; Fig. 8 is a cross-sectional view through a melter constructed in accordance with a third embodiment of the present invention; Fig. 9 is a side view showing the melter of Fig. 8 in cross section; .and, Fig. 10 is a view taken along view line 10- 10 in Fig. 9. MODES FOR CARRYING OUT THE INVENTION An apparatus 10 constructed in accordance with the present invention for supplying streams of molten glass to be drawn into continuous glass fibers is illustrated in Figs. 1 and 2. The apparatus 10 comprises a melter 20, a screw-metering device 30 for delivering glass-forming batch materials 40 to the melter 20, and a plurality of bushing assemblies 80 located directly below the melter 20. The bushing assemblies 80 comprise bushings 50 having a plurality of nozzles 53 which supply streams of molten glass to be mechanically drawn into continuous glass fibers via a conventional winder or like device (not shown), see Fig. 4. The melter 20 comprises a receptacle 22 and a plurality of heating devices 24. The receptacle 22 is formed of conventional refractory materials 26 which are retained in position by appropriate supporting metal framework and foundations (not shown). The receptacle 22 receives glass-forming batch materials 40 from the screw-metering device 30. The receptacle 22 has a length L, width W and height H. The metering device 30 extends along substantially the entire length L of the receptacle 22 and, upon actuation of a screw 32 within the device 30, dispenses batch materials 40 to the receptacle 22, see Fig. 2. The batch materials 40 comprise conventional glass-making ingredients which may be conventional pure glass-making ingredients, recycled ingredients, i.e. cullet, or a combination of both. The ingredients are preferably combined and mixed in a conventional pneumatic mixer 60 (shown schematically in Fig. 2), one of which is commercially available from Nol-Tec Systems Incorporated, Lino Lakes, Minnesota, under the product name Bin Blender. The mixer 60, via pneumatic jets, acts to homogenize the conventional glass-making ingredients such that they are very uniform in consistency. It is important that the glass-making ingredients be thoroughly mixed before being added to the melter 20 as there is little time for the ingredients to homogenize in the melter 20. The batch materials 40 are pneumatically conveyed from the mixer 60 to the screw-metering device 30 through piping 62. Each of the heating devices 24 comprises a pair of heating electrodes 52 and of which is hereby incorporated by reference. The heating electrodes 52 and 54 are maintained in position over the receptacle 22 via brackets 52a and 54a which, in the illustrated embodiment, are attached to the receptacle 22. The electrodes 52 and 54 extend down through a layer 40a of the cold glass-forming batch materials 40 and into a pool 42a 5 of molten glass material 42. The heating devices 24 are spaced apart from one another along the length L of the receptacle 22, see Fig. 2. Each set of electrodes 52 and 54 is connected to a conventional power supply (not shown) which supplies heating current to the electrodes 52 and 54 to heat the pool 42a of molten glass material 42. The primary heating path is from one electrode tip 10 52b to an opposing electrode tip 54b of opposite polarity. Because the electrode tips 52b and 54b extend only part way down into the pool 42a of molten glass material 42, see Fig. 1 , the molten glass material 42 is permitted to cool somewhat as it moves down towards the bottom portion 22a of the receptacle 22. This is important since the molten glass material 42 flowing into the bushings 50 is preferably at a temperature such that the molten glass 15 material flowing from the bushing nozzles 53 can be quickly cooled or quenched. If the temperature of the molten glass material 42 delivered to the bushings 50 is too high, the glass material may not be able to cool sufficiently to become viscous enough for fiber forming. An advantage to having the electrodes 52 and 54 extend down into the 20 receptacle 22 rather than through a side or bottom wall of the receptacle 22 is that a potential problem of short-circuiting through the refractory material 26, i.e., current flow through refractory material located between two electrodes 52 and 54 rather than through the glass material, is eliminated. Another advantage is that the electrodes 52 and 54 can be easily repositioned such that the spacing between the electrodes 52 and 54 can be adjusted. 25 The resistivity of the particular glass composition being attenuated into glass fibers is one factor to consider in determining the desired spacing between the electrodes 52 and 54. The bottom portion 22a of the receptacle 22 includes a plurality of openings 70 through which primary streams 42b of molten glass material 42 flow to the bushing assemblies 80. A single bushing assembly 80 is associated with each opening 70. see Fig. 30 4. Each bushing assembly 80 includes a bushing 50 (also referred to herein as a bushing device). The bushing 50 is encased in refractory material 51 which, in turn, is encased in a metal frame 51a. The bushing assembly 80 further includes a bushing block 56 (also referred to herein as a receiving block) which is interposed between the bushing 50 and a first section 22b of the bottom portion 22a of the receptacle 22. The bushing block 56 is received in a recess 22c defined in a second section 22d of the bottom portion 22a of the receptacle 22. The bushing block 56 includes an orifice 56a which, when the bushing block 56 is received in the recess 22c, is in general alignment with one of the openings 70 through which a primary stream 42b of molten glass material passes. Hence, the orifice 56a receives one of the primary streams 42b of molten glass material 42 flowing from one of the openings 70 in the bottom portion 22a of the receptacle 22. It is contemplated by the present invention that the bushing assemblies 80 may comprise a bushing 50 without a bushing block 56. When a bushing block 56 is not employed, the bushing 50 is mechanically held in place against the first section 22b such as by clamps. The bushing 50 includes a flange 50a which contacts the underside 56b of the bushing block 56. A cooling coil 90 is clipped or otherwise secured to the underside of the bushing flange 50a and extends about substantially the entire perimeter of the flange 50a. The cooling coil 90 communicates with a cooling fluid source (not shown) which provides a cooling fluid, e.g., water, to the cooling coil 90. As the cooling fluid circulates through the cooling coil 90, glass material which makes its way between the bushing flange 50a and the bushing block 56 substantially freezes or solidifies to effect a seal between the bushing block 56 and the bushing 50. Located below each bushing 50 is a heat removal apparatus (not shown) which is adapted to remove heat from the fiber forming region 50b below each bushing 50. The heat removal apparatus may comprise a plurality of fins which are conductively associated with one or two water-cooled manifolds. For example, the heat removal apparatus may be constructed in the manner described in either of commonly assigned U.S. Patent Nos. 4,541,853 and 4,571,251, the disclosures of which are hereby incorporated by reference. The temperature of the glass within each bushing 50 must be sufficiently high such that the glass is in a fluid state. However, it should not be so high that it prevents the glass, after passing through the bushing nozzles 53, from cooling and becoming viscous enough for fiber forming. Because forehearths and delivery channels do not form part of the apparatus 10 of the present invention, the molten glass 42 has little time to cool after it has been heated to the temperature required to effect melting of the initial glass- forming batch materials. Thus, it is contemplated that the temperature of the molten glass material 42 delivered to the bushings 50 may be higher than normal. In order to compensate for the higher-than-normal glass material temperatures within the bushings 50, each bushing 50 is preferably provided with only 400 nozzles 53 and most preferably with only about 200 nozzles 53. Hence, an acceptable rate of heat removal from the fiber forming region 50b just below each bushing 50 can be attained via the heat removal apparatus. Thus, the molten glass material 42 can be quickly cooled or quenched in the fiber forming region 50b to allow for satisfactory attenuation. The glass pressure head in the melter 20, which is equal to the combined height H c of the pool 42a of molten glass material 42 and the layer 40a of the cold glass- forming batch materials 40 (see Fig. 1) falls within the range of approximately 30 inches to 36 inches (0.75m to 0.9m). In conventional glass fiber forming processes, where the molten glass material is delivered to a bushing from a forehearth, the glass pressure head in the forehearth is approximately 3 inches to 6 inches (0.075m to 0.15m). Because of the substantial increase in the glass pressure head as well as the higher-than-normal temperature of the molten glass material 40 delivered to the bushings 50 in the present invention, the same molten glass material throughput rate through the nozzles 53 can be achieved with smaller bushing nozzles 53. Hence, the bushings 50 can be made smaller. It is also contemplated that because of the increase in the glass pressure head the bushings 50 may be provided with more effective screens (not shown), i.e., screens having finer meshes, which act to screen out devitrified glass crystals. Such crystals may form in the melter 22 and can migrate to the bushing 50 and cause fiber breakout resulting in a shut-down of the fiber forming operation. With more effective screens, the number of fiber-breakouts can be reduced. The bushings 50 are preferably formed from a platinum alloy. As the temperature of the molten glass 42 delivered to the bushings 50 increases and as the glass pressure head increases, the likelihood that the bushings 50 may sag, e.g., deform downwardly, due to the weight of the molten glass 42 supported by the bushings 50 increases. However, because the bushings 50 have only a limited number of nozzles 53, they are smaller than normal. For example, a bushing 50 having about 200 nozzles may be 3 inches by 3 inches (0.075m by 0.75m) in length and width and 1.5 inches (0.0375m) in 5 height H B , see Fig. 4. The smaller-than-normal bushings 50 are easier to support and less likely to sag. A further advantage to using a bushing 50 having fewer nozzles 53 is that it is easier to control the temperature of each bushing 50 both spatially and temporally. Hence, the fiber forming operation is more consistent, controllable and predictable. 10 In the embodiment illustrated in Figs. 1-3, there are seven rows 70a of openings 70 spaced apart from one another along the length L of the receptacle 22. Each row 70a has six adjacent openings 70. Correspondingly, there are seven rows of bushing assemblies 80 spaced apart from one another along the length L of the receptacle 22, with each row having six adjacent bushing assemblies 80. Preferably, each bushing 50 includes 15 400 nozzles 53 and most preferably 200 nozzles 53. Seven conventional winder devices (not shown) are provided, one for each row of bushing assemblies 80. Each winder device includes six rotatable mandrels for supporting six packaging sleeves upon which six strands of fibers from the six associated bushings 50 are wound into packages. The inner width W, of the receptacle 22 is approximately 5 feet (1.5m) and the length L of the receptacle 22 is 0 approximately 30 feet (9m), see Figs. 1 and 2. A further advantage to using bushings 50 having a limited number of nozzles 53 is that should an interruption in the attenuation of molten glass streams to fibers occur at one bushing 50, it impacts fiber production of only 200 or 400 fibers. Thus, in the embodiment illustrated in Figs. 1-3, should fiber breakout occur at one bushing 50 in a 5 given row, fiber production at the other six bushings 50 in that row may continue until their corresponding packages have been formed. In contrast, when fiber breakout occurs during use of a typical conventional bushing having 1000 or more nozzles, it impacts fiber production of 1000 or more fibers. An apparatus 100 constructed in accordance with a second embodiment of 0 the present invention for supplying streams of molten glass to be drawn into continuous glass fibers is shown in Figs. 5-7, wherein like reference numerals indicate like elements. The apparatus 100 is constructed in essentially the same manner as the apparatus 10 illustrated in Figs. 1-3. It differs from the apparatus 10 in that it includes a receptacle 122 having a single row of openings 70 and has a single row of bushing assemblies 80 located directly below the receptacle 122. An apparatus 200 constructed in accordance with a third embodiment of the present invention for supplying streams of molten glass to be drawn into continuous glass fibers is shown in Figs. 8-10, wherein like reference numerals indicate like elements. The apparatus 200 is constructed in essentially the same manner as the apparatus 10 illustrated in Figs. 1-3. It differs from the apparatus 10 in that the receptacle 222 includes first and second rows 124a and 124b of openings 70 spaced apart from one .another along the width W of the receptacle 222. The openings 70 defining the first row 124a are positioned such that they are located along axes A, which are orthogonal to a longitudinal axis A ( of the receptacle 22. The openings 70 defining the second row 124b are positioned along axes A 2 which are generally parallel to and spaced from adjacent axes A,. While it is preferred to provide bushings having 400 bushing nozzles or less, it is contemplated by the present invention that bushings having more than 400 bushing nozzles may be employed. Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

Claims: CLAIMS 1. An apparatus for supplying streams of molten glass to be drawn into continuous glass fibers comprising: a receptacle (22) for receiving glass-forming batch materials (40) to be melted into molten glass material (42) such that a pool (42a) of molten glass material is provided in said receptacle below a layer (40a) of glass-forming batch materials and including a plurality of openings (70) through which primary streams (42b) of molten glass material flow from said receptacle (22); a device (30) for feeding said glass-forming batch materials to said receptacle; a heating device (24) associated with said receptacle for generating heat to melt said glass-forming batch materials; and a plurality of bushings (50) located adjacent to said receptacle such that each of said bushings receives one of said primary streams of molten glass material, and said bushings including a plurality of nozzles (53) for supplying secondary streams of molten glass material to be drawn into continuous fibers. 2. An apparatus as set forth in claim 1 , further including a plurality of receiving blocks (56) each located between said receptacle and one of said bushings. 3. An apparatus as set forth in claim 1 , wherein said receptacle has a length, width and height and includes two or more rows of openings (70) spaced a given distance from one another along the length of said receptacle with each row including at least two adjacent openings. 4. An apparatus as set forth in claim 3, wherein said receptacle includes seven rows (70a) of openings (70) spaced apart from one another along the length of said receptacle with each row having six adjacent openings. 5. An apparatus as set forth in claim 1 , wherein said receptacle has a length, width and height and includes first and second rows (124a and 124b) of openings (70) spaced from one another along the width of said receptacle. 6. An apparatus as set forth in claim 5, wherein said receptacle has a longitudinal axis and said openings (70) defining said first row (124a) do not share a common axis which is orthogonal to said longitudinal axis with any one of said openings defining said second row (124b). 7. An apparatus as set forth in claim 1 , wherein said feeding device (30) comprises a screw-metering device which uniformly applies glass-forming materials to said receptacle. 8. An apparatus as set forth in claim 1 , wherein said heating device (24) is positioned over said receptacle and extends down through said layer (40a) of glass- forming batch materials (40) and into said pool (42a) of molten glass material (42). 9. An apparatus as set forth in claim 8, wherein said heating device (24) comprises at least one set of heating electrodes (52 and 54) of opposite polarity. 10. An apparatus as set forth in claim 8, wherein said receptacle has a length, width and height and said heating device comprises a plurality of sets of heating electrodes (52 and 54) of opposite polarity with said sets being spaced apart from one another along the length of said receptacle. 1 1. An apparatus as set forth in claim 1 , wherein each of said bushings (50) includes approximately 400 nozzles (53) or less. 12. An apparatus as set forth in claim 1, wherein each of said bushings (50) includes approximately 200 nozzles (53) or less. 13. An apparatus for supplying streams of molten glass to be drawn into continuous glass fibers comprising: a receptacle (22) for receiving glass-forming batch materials (40) to be melted into molten glass material (42) such that a pool (42a) of molten glass material (42) is provided in said receptacle below a layer (40a) of glass-forming batch materials (40) and including at least one opening (70) through which a primary stream (42b) of molten glass material flows from said receptacle (22); a device (30) for feeding said glass-forming batch materials to said receptacle; a heating device (24) associated with said receptacle for generating heat to melt said glass-forming batch materials, said heating device is positioned over said receptacle and extends down through said layer of glass-forming batch materials and into said pool of molten glass material; and at least one bushing (50) located adjacent to said receptacle such that said bushing receives said primary stream of molten glass material passing through said opening in said receptacle, and said bushing including a plurality of nozzles (53) for supplying secondary streams of molten glass material to be drawn into continuous fibers. 14. An apparatus as set forth in claim 13, further including a receiving block (56) located between said receptacle and said bushing. 15. An apparatus as set forth in claim 13, wherein said feeding device (30) comprises a screw-metering device which controls the amount of glass-forming materials fed to said receptacle. 16. An apparatus as set forth in claim 13, wherein said heating device (24) comprises at least one set of heating electrodes (52 and 54) of opposite polarity. 17. A method for supplying streams of molten glass to be drawn into continuous glass fibers comprising the steps of: providing a substantially homogeneous blend of glass-forming batch materials; feeding said homogeneous batch materials to a melter (20); supplying heat to said melter to effect melting of said batch materials into molten glass material; supplying a stream (42b) of molten glass material from said melter directly to a bushing assembly (80); supplying from said bushing assembly a plurality of secondary streams of molten glass material to be drawn into continuous fibers. 18. A method as set forth in claim 17, wherein said bushing assembly comprises a bushing device (50) provided directly adjacent to said melter. 19. A method as set forth in claim 17, wherein said bushing assembly comprises a bushing device (50) and a receiving block (56) with said receiving block being located between said melter and said bushing device. 20. A method as set forth in claim 17, wherein said step of providing a substantially homogenous blend of batch materials comprises the steps of providing a pneumatic mixer (60) and blending said glass-forming batch materials using said pneumatic mixer.

Inventors: O'BRIEN-BERNINI FRANK C, WINGERT JOHN W, O'BRIEN-BERNINI, FRANK, C., WINGERT, JOHN, W.
Applicants: OWENS CORNING FIBERGLASS CORP, OWENS CORNING
Application year: 1997
Main classification: C03B37
IPC codes: C03B37