Glass manufacturing – Fiber making apparatus – With specified bushing – tip – or feeder structure
Reexamination Certificate
2001-06-27
2004-11-09
Griffin, Steven P. (Department: 1731)
Glass manufacturing
Fiber making apparatus
With specified bushing, tip, or feeder structure
C065S499000, C065S492000, C065S493000, C065S494000, C373S028000
Reexamination Certificate
active
06813909
ABSTRACT:
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
The present invention relates generally to bushings for forming fibers from a fluid material, such as glass at an elevated temperature and more particularly, to an improved manner of reinforcing a bushing tip plate to extend the service life thereof.
BACKGROUND OF THE INVENTION
Various types of bushings or bushing assemblies for forming fibers or filaments from a fluid material, such as glass at an elevated temperature, are known in the art. Usually, the bushing or bushing assembly includes a rectangular bushing body having sidewalls and end walls. Together, the side and end walls serve as a frame for supporting or carrying one or more, often elongated plate-like structures, typically formed of platinum or alloys thereof, having a plurality of small orifices or “tips.” These tips receive the molten material as it passes through the bushing body from an upstream source, such as a forehearth. To assist in keeping the material in a molten state as it enters and passes through these tips, the plates are heated, usually by electrically coupling them to a source of high current, such as a transformer. As molten glass material streams exit the tips, they are mechanically drawn to form continuous fibers which are wound onto mandrels or creels or directly chopped for later processing or use. A detailed description of the basic apparatus and methodology used is found in commonly assigned U.S. Pat. No. 5,709,727 to Bobba and U.S. Pat. No. 3,920,430 to Carey, the disclosures of which are incorporated herein by reference.
To improve the output and efficiency of the overall fiber-forming operation, it is of course desirable to maximize the number of fibers created by the tip plate. To do so, a tip plate can in theory be made infinitely large in both the width and length dimensions. However, several well-recognized problems arise, especially when the width dimension of a tip plate is significantly increased relative to the length dimension.
Perhaps the most prevalent problem resulting from increasing the dimensions of the tip plate, and in particular, the width dimension, to the degree necessary to realize a significant increase in fiber output is a sharp reduction in the service life. The tip plate is normally rectangular in top plan view, with its four side edges welded directly to the opposed side and end walls of the rectangular bushing body. When the width dimension of the tip plate increases relative to the length dimension, the plate essentially acts as a simple beam supported at the sides and ends, with no direct support at the “middle” (i.e., the portion furthest from the side and end walls of the corresponding bushing body). Significant bending stresses acting on the tip plate as the result of prolonged contact with the heavy molten material over time results in sagging due to time dependent plastic deformation, or creep. This sagging is deleterious primarily because it results in non-uniform thermal distribution and the concomitant production of fibers having substantially different diameters across the tip plate. That is, the extremes in temperature cause some bushing tips to become too cold to attenuate a fiber and others are hot enough to cause a forming instability. Both cases cause fiber breakage and a loss in conversion efficiency.
Reducing the width dimension of the plate is therefore desirable to curtail the effects of creep and increase the service life. However, the trade-off is an undesirable reduction in output and a concomitant increase in cost when only a single narrow-width tip plate is used. Also, after prolonged use, even a single narrow-width tip plate eventually suffers from creep-induced sagging, non-uniform fiber output, and increased fiber break rates.
In an effort to increase the service life of a bushing tip plate to overcome this problem and others, the present Assignee has in the past employed reinforcing members formed of platinum or a platinum alloy, termed “gussets.” These gussets usually extend width-wise across the upper surface of the tip plate (i.e., between the sidewalls of the bushing body) at spaced intervals, and typically have a cross-section that corresponds in shape to a “T” or inverted “L.” In use, the depending “leg” formed by the web of each gusset is secured directly to the upper surface of the tip plate, such as by laser or tungsten-inert gas (TIG) welding.
While these gussets do serve to extend the service life of the tip plate, including even in the narrow-width case, the degree of the benefit gained is somewhat limited. In particular, the gussets having a T-shaped or inverted L-shaped cross-section are also susceptible to sagging due to bending stresses and creep as the underlying tip plate. This is because the gusset, while providing some reinforcement strength, also behaves like a simple beam, and thus experiences maximum deflection at the span midpoint as in an unsupported tip plate. In other words, despite the reinforcement, the maximum or peak stress and hence, the maximum or peak sag, still occurs at the middle of the tip plate away from the side and end walls. Accordingly, a need for an improved manner of reinforcing tip plates, including those existing bushing designs (with or without gussets) with an eye toward further extending their service life is identified.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, a reinforcement member for a bushing assembly having a plate-like structure including a plurality of orifices for forming fibers from a fluid material is provided. The member comprises a body including a first portion for attachment to the structure and a second portion having a profile with a variable height including at least one apex. The variable height profile and the at least one apex of the body assists in reinforcing the plate-like structure against sagging and extends the service life thereof without undue alloy usage.
In one embodiment, the reinforcement member is comprised of a single piece of material, with the body including the first and second portions having an inverted L-shaped, T-shaped, or F-shaped cross-section. The profile of the second portion of the body may have an inverted V-shaped, inverted W-shaped, or arcuate profile. Preferably, the body has a length including a midpoint, with the at least one apex located substantially at the midpoint. The midpoint may also be the midpoint between the spaced sidewalls or external support points of the bushing assembly to which a first and a second end of the body are secured.
In other embodiments, the body comprises a first member defining the first portion for attachment to the structure and a second member coupled with the first member, defining the second portion and having the variable height profile with the at least one apex. The first member may have a T-shape or an inverted L-shape in cross-section. Likewise, the second member may have a T-shape or an inverted L-shape in cross-section, and may be formed from one or more component parts. Additionally, the second portion may have an arcuate profile, an inverted V-shaped profile, or an inverted W-shaped profile, each including the at least one apex. Preferably, the second member includes a web having an end that is welded directly to an upper surface of the first member, and optionally may have a profile that defines two or more apexes. In any of the embodiments, either the first or second portion of the body may include a plurality of strategically positioned openings. These openings serve to reduce the amount of material required to fabricate the reinforcement member without compromising the strength thereof.
In accordance with a second aspect of the invention, a bushing assembly for use of forming a plurality of fibers from a fluid material at an elevated temperature is disclosed. The assembly comprises a structure having a plurality of orifices through which the fluid material passes to form the fibers and at least one reinforcement member. This member comprises a first portion for attachment to the structur
Bemis Byron L.
Emerson Jack L.
Purnode Bruno A.
Smith Kevin D.
Streicher William L.
Eckert Inger H.
Gasaway Maria C.
Griffin Steven P.
Halpern Mark
Owens Corning Fiberglas Technology Inc.
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