Abstract:
A reinforcement device, especially for the bottom of a bushing having a multitude of holes from which filaments, e.g., glass filaments, are drawn, including a reinforcement piece that includes a hollow first part defining at least one receiving housing and a second part that extends at least partly over the length of the hollow part, and also at least one stiffener inserted into the receiving housing of the hollow part. The cross section of the stiffener is substantially identical to the internal cross section of the hollow part.

Description:
This application is a 371 of PCT/FR04/00255 filed on 4 Feb. 2004. 
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The invention relates to a fiberizing installation delivering fibers, especially glass fibers, and more particularly to the mechanical reinforcement of one of the components of the fiberizing installation. 
     II. Description of Related Art 
     Conventionally, a fiberizing installation comprises a glass flow block, which receives molten glass coming from a feeder connected to the furnace in which the glass is melted, a bushing block and a bushing. The bushing is provided at the bottom with a plate provided with a multitude of holes from which the molten glass flows, to be drawn into a multiplicity of filaments. 
     These filaments, the diameter of which may vary from 5 to 33 μm, are collected into at least one sheet that converges on an assembling device in order to form at least one strand and, for example, to be wound up. Depending on its use, the strand may also be chopped (to form chopped strands) or thrown onto a belt (to form continuous strand mats). 
     The products obtained are used mainly in various reinforcing applications. 
     The bushing is manufactured from an alloy of platinum and rhodium, which materials are electrically conducting and resistant over time to very high temperatures. This bushing is heated by the Joule effect (resistance heating) so as to maintain, at a certain temperature, around 1100 to 1400° C., the glass that it contains so that it remains in the molten state so as to be drawn from the holes in the bottom of the bushing. The bushing is heated using an electrical transformer by the connection of two terminals, each located on each of the opposed ends of the bushing, to electrical connection components external to the bushing. 
     The terminals of the bushing are attached by welding them to the side walls of the bushing. They project so as to be connected to the external connection components. 
     Placed inside the bushing, in a plane substantially parallel to the bottom of the bushing and on the bushing block side, is a screen intended to thermally condition the glass and to absorb some of the hydrostatic pressure exerted by the molten glass. 
     The molten glass exerts high stresses, of around 6000 Pa, on the sides, the screen and the bottom of the bushing. Over the course of time, these stresses, combined with the heat, tend to distort the bottom, the screen and the sides of the bushing. Furthermore, the external electrical connection components connected to the terminals of the bushing are suspended therefrom, exerting an additional mechanical tensile force on the bushing, which also causes the bushing to deform over time. 
     Over the course of time, the hot creep of the constituent materials of the bushing, combined with the hydrostatic pressure of the molten glass, tends to deform the bottom, the screen and the sides, consequently causing strand quality and titer uniformity problems and yield problems. 
     The tensile forces (weight) of the suspended components and the linear expansion of the walls of the bushing also induce high mechanical stresses. 
     So as partly to prevent deformation of the bushing, it is known to add, in the upper part of the bottom of the bushing and between its sides, a plurality of mutually parallel reinforcement components lying in planes transverse to the plane of the bottom of the bushing and transversely to the longest sides of the bushing. In the rest of the description, the terms upper and lower are defined relative to the flow direction of the glass through the bushing, the glass being drawn from the upper part toward the lower part. 
     U.S. Pat. No. 3,920,430 discloses such a reinforcement component or device which helps to improve its resistance to bending, while not increasing the weight of platinum or platinum alloy needed for its construction, by additionally providing a ceramic rod placed inside the reinforcement component. 
     In that document, the reinforcement component consisting of a longitudinal bar is hollow and houses a ceramic rod that extends beyond each of the ends of the reinforcement bar and is anchored into the concrete for packing the bushing. That document insists on the fact that the rod is placed in the upper part of the reinforcement bar, bearing on the upper internal wall of the bar and leaving an empty space in the lower part of the bar. 
     However, this reinforcement bar, owing in particular to the internal empty space in the lower part, is not sufficiently resistant to bending. Furthermore, owing to the platinum creep temperature, the bar deforms, its lower part slumps and the thrust forces exerted by the glass on the bottom of the bushing end up by deforming it. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore the object of the invention to provide a reinforcement device making it possible to improve the resistance to the bending resulting from the alloy creeping and to stabilize its thermal level over the time it is in operation. 
     The reinforcement device, especially for the bottom of a bushing having a multitude of holes from which filaments, especially glass filaments are drawn, comprising a reinforcement piece that comprises a hollow first part defining at least one receiving housing and a second part that extends at least partly over the length of the hollow part, and also at least one stiffener inserted into the receiving housing of the hollow part, is characterized in that the cross section of the stiffener is substantially identical to the internal cross section of the hollow part. 
     According to one feature, the device includes a refractory additional material placed in the receiving housing of the hollow part between the stiffener and the internal walls of the hollow part so as to fill the remaining spaces in the manner of a seal. This refractory additional material is preferably a refractory plastic insulator. 
     Advantageously, the stiffener is made of at least one material whose hot creep resistance is greater than the hot creep resistance of the material of which the hollow part is made. This material may be of the ceramic type, such as alumina with a purety of at least 99.5% and preferably 99.7 to 99.8%. This material may also be an iron-based or nickel-based or titanium-based ODS alloy. 
     According to another feature of the device, the hollow part has an oblong shape that extends along a single direction, or else it may rather have a shape in the manner of an upside down V, comprising two portions extending along two different directions and coming into abutment in a joint plane. In the latter variant, the two portions of the hollow element constitute two respective receiving housings into each of which at least one stiffener is inserted. 
     According to another feature, the hollow part is made of a single piece, or else in the variant of the two portions of the hollow part, it may be made of two pieces fastened together. 
     According to yet another feature, the hollow part has a cross section of square, rectangular, round, oval, triangular or trapezoidal shape. 
     Preferably, the reinforcement piece is made of a platinum alloy. 
     Finally, the body of the reinforcement piece preferably has a third part on the opposite side from the second part and extending at least partly over the length of the hollow part. 
     According to the invention, at least one reinforcement device may advantageously be used in a bushing, the reinforcement device or devices extending in a plane transverse to the longest sides of the bushing, and the ends of the stiffener or stiffeners extending from the hollow part and being fastened into the concrete for packing the bushing, the whole assembly thus forming an undeformable block. 
     According to one feature, the device is attached to the bottom by attaching the longitudinal free end of the second part of the reinforcement piece and the lateral free ends of the hollow part of the reinforcement piece. 
     According to another feature, the bushing includes a screen placed on top of the reinforcement device or devices, the third part of the reinforcement piece being fastened to the screen. 
     Other advantages and features of the invention will now be described in greater detail with regard to the appended drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a partial view of the bottom of a bushing to which a plurality of reinforcement devices of the invention are added; 
         FIG. 2  shows a side view of a reinforcement device of the invention; 
         FIGS. 3 and 4  are variants of  FIG. 2 ; and 
         FIG. 5  is a cross-sectional view of various shapes of the reinforcement device added to the bottom of the bushing and to the screen of the bushing. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates several reinforcement devices  1  of the invention that are added to a plate  20  of the bottom  2  of a bushing (not shown in detail) and intended to form part of a fiberizing installation capable of delivering, for example from molten glass, glass filaments. 
     The bottom  2  comprises a rectangular plate  20  having opposed sides  21  that will be called the long sides, and shorter sides  22  perpendicular to these long sides that will be called the short sides. The long sides  21  are provided with perpendicular flanges  23  extending from the upper face  2   a  of the plate  20 . 
     Arranged on the lower face  2   b  of the plate  20  are nipples  3  that are drilled with holes from which the glass is drawn into filaments. 
     The devices  1  are placed so as to be inserted between the rows of nipples so as not to disturb the flow of glass through the latter, for example between two double rows. 
     Each reinforcement device  1  as illustrated in detail in  FIGS. 2 to 4  comprises a reinforcement piece  10  and at least one stiffener  40 . 
     The reinforcement piece  10  comprises a longitudinal body  11  that has a central hollow first part  12  and a lower second part  13  which will be called the skirt and which extends over part or the entire length of the hollow part  12 . 
     The device is joined to the bottom  2  in such a way that the body  11  extends in a direction transverse to the long sides  21 , the opposed lateral free ends  14  and  15  of the hollow part being fastened to the flanges  23  and projecting from these flanges, and the longitudinal end  13   a  of the skirt  13  of the body being fastened to the upper face  2   a  of the plate  20 . 
     To limit the weight of the reinforcement piece, the skirt  13  may advantageously be drilled with holes ( FIG. 4 ) or else consist of several parts spaced apart along the length of the hollow part  12  (not illustrated). 
     The central hollow part  12  of the reinforcement piece defines at least one receiving housing for at least one stiffener  40 , the ends  41 ,  42  of said stiffener, after it has been inserted, projecting from the respective lateral ends  14  and  15  of the hollow part. 
     The ends  41 ,  42  of the stiffener are anchored in the concrete (not illustrated) for packing the bushing. This results in complete consolidation of the assembly formed by the bushing and by the packing concrete, which too is nondeformable. 
     The hollow part  12  may have cross sections of various shapes ( FIG. 5 ), for example square, rectangular, round, oval, triangular or trapezoidal shapes, the stiffener  40  preferably having a cross section substantially identical to the internal cross section of the hollow part in order for it to be tightly inserted into the housing. 
     The hollow part  12  may extend along a single direction, as shown in  FIGS. 2 and 3 . A single stiffener  40 , which is in the form of a rod of approximately identical cross section, section, is then placed in the receiving housing. 
     As a variant, ( FIG. 4 ), the hollow part  12  may extend along two directions that intersect in the upper part of the body, on the opposite side from the skirt  13 , and in a joint plane P, to form two portions  12   a  and  12   b , the whole assembly thus having a cross section in the form of an upside down V in the manner of a roof truss, which, as is well known, exhibits better resistance to bending. 
     This configuration is produced as a single piece or else as at least two pieces welded along the joint plane P. In this variant, the portions  12   a  and  12   b  provide at least two receiving housings for two respective stiffeners  40 , the ends of the stiffeners  40  in the plane P having to be contiguous over their entire surface. 
     The body  11  of the reinforcement piece  10  is made of platinum alloy material, which may or may not be similar to the bottom of the bushing, whereas the stiffener  40  is made of a material other than platinum and whose hot creep strength is greater than the hot creep strength of the material of which the reinforcement piece is made. The reinforcement device is thus lighter than if the central part  12  were to be solid and made of platinum. 
     The material of the stiffener  40  may be a material of the ceramic type, such as alumina, silicon nitride or zirconia, or else of the nickel-based or iron-based or titanium-based (ODS Oxide-Dispersion-Strengthened) alloy type, or else of the refractory alloy type, especially one based on tungsten or molybdenum or niobium, although this type of alloy is expensive. 
     The ceramic-type material has the advantage of not forming a eutectic with platinum. 
     The ODS alloy type material has the advantage of being able to be used at very high temperatures, of around 1500 to close to 1700° C. 
     Advantageously, a refractory additional material  50  is provided, this being introduced into the spaces remaining between the internal walls of the part  12  and the stiffener  40  after it has been housed, in the manner of a seal so as to immobilize the stiffener  40  in its housing and to prevent any deformation of the hollow part  12 . This material  50  is, for example, a refractory plastic insulator, such as the material REFRACTOL® from the company Réfractol. 
     There is therefore complete rigidity of the entire reinforcement piece, without any risk, as in the prior art, of deformation of the hollow reinforcement piece around the inner rod causing the skirt to slump and the bottom to deform. Furthermore, there is no space inside the hollow part  12 , thereby preventing, unlike the prior art, platinum being sublimed on the stiffener. Thus, platinum losses are minimized, resulting in cost savings when recycling the platinum after the end of operation of the bushing. 
     The body  11  is attached to the bottom  2  of the bushing by welding, firstly by fastening the longitudinal end  13   a  of the lower part against the upper face  2   a  of the bottom and, secondly, fastening the opposed lateral free ends  14  and  15  of the hollow part, coming through the flanges  23 . 
     Optionally and preferably, the body  11  includes an upper, third part  17  placed on the opposite side from the lower part  12  and extending over part or the entire length of the hollow part  12 . This upper part  17  is used to support the screen  4  of the bushing and prevents it from deforming. This upper part  17  is attached to the screen spontaneously by metal diffusion during the operation of the bushing (once it has been heated up and during the first few days of operation). 
     This additional attachment in the upper part thus ensures that all the elements of the bushing are completely consolidated. 
     The bushing thus constitutes a nondeformable rigid block. The thermal image and the head loss are retained. The operation of the bushing is thereby facilitated, in particular avoiding interruptions to the fiberizing process for adjustment. The quality of the product obtained is constant over time and the manufacturing yield is higher.