Patent Application
20050092031
The present invention involves fluid cooled, directly or indirectly, parts for fiberizing bushings such as cooling tubes that cool the tips that form fibers from a molten material, the meniscus at the end of each tip and the fibers as they emerge from the meniscus. The present invention also includes fluid-cooled, directly or indirectly, parts for fiberizing bushings that do not have fiber forming tips, but that form fibers under an orifice plate and the method of using these cooling parts.
In the manufacture of continuous fibers from a molten material like molten glass, the molten material is often generated by a tank furnace and distributed to a plurality of fiberizing bushings via one or more channels and into one or more bushing legs connected to the channel's). Each bushing leg comes off the channel at about 90 degrees and contains a plurality of spaced apart orifices in the bottom to supply bushings that are mounted to the underneath side of each leg.
Precious metal bushings made from alloys of platinum and rhodium and used for making continuous glass fibers are well known, having been in use for more than 50 years. Many types of bushings exist for converting molten glass into continuous glass fiber and products. Typical types of bushings are shown in U.S. Pat. Nos. 3,512,948, 4,155,732, 4,272,271 and 4,285,712, the disclosures of which are hereby incorporated by reference. All the bushings shown in these patents teach the use of a perforated plate or screen, welded to the end walls and sidewalls at some distance above a tip plate containing hundreds or thousands of nozzles or tips where molten glass first emerges from the bushing and is converted to continuous glass fibers by cooling and drawing, attenuating, in a known manner.
It is typical to use cooling tubes, with or without one or more short fins attached, suspended below the tip plate and located close to the tips to cool the molten tips and the molten glass as it emerges from the tips and as the molten glass is attenuated or drawn into fibers of desired diameter. Some previous patents which show cooling tubes are U.S. Pat. Nos. 4,337,075, 4,397,665, and 5,244,483, the disclosure of which is incorporated herein by reference. During operation cooling water flows through the cooling tubes to carry away heat absorbed by the cooling tubes. It is also known to use solid and/or hollow cooling fins and other cooling apparatus below the tip plate to remove heat from below the tip plate as shown in U.S. Pat. Nos. 3,264,076, 3,708,271, 3,746,525, 4,824,457, 5,693,118, 5,925,164, 6,192,714, and 6,408,654, the disclosures of which are incorporated herein by reference.
The outer surface of the cooling tubes and/or fins are subjected to very corrosive conditions of high temperature, oxidizing conditions, corrosive vapors coming off of the molten glass and a water or high humidity. While nickel has been used, experience has been an unacceptable short service life, particularly where the containment of cooling fluid is involved. Nickel and copper also oxidize excessively on the exposed surface that reduces their thermal conductivity. Copper suffers catastrophic failure when cooling fluid is lost for a period of time that can happen when power is lost for a period of time. To achieve practical life and good fiberizing performance, it has been ordinary practice to use precious metals and precious metal alloys for cooling tubes. It has been preferred to use a precious metal or a precious metal alloy of platinum, rhodium, palladium, etc. that can be bent fairly easily while mounted in place to allow appropriate location adjustment as the tip plate and tips deform significantly during service, usually more in some parts of the tip plate than other parts.
As disclosed in U.S. Pat. No. 4,397,665, it is known to make cooling tubes by cladding a base metal with a layer of platinum, palladium, rhodium, iridium, gold, silver or alloys thereof, but this technique proved to be too expensive. Any flaw in the cladding resulted in premature failure and the failures added further costs. Alloys of platinum and rhodium were used for many years to make cooling tubes, but rhodium became extremely expensive. Palladium was tried alone, but it proved too soft and the tubes were too easily damaged during routine maintenance and operation of the bushing.
U.S. Pat. No. 5,749,933 discloses using an alloy of palladium containing a small percentage of ruthenium to reduce the investment, but this alloy was more rigid than desired. This patent taught that alloys of palladium containing small amounts of iridium or nickel produced more desirable cooling tubes. While these alloys are much less expensive than platinum and rhodium, they are still very expensive compared to non-precious metal alloys and it is still desirable to find a way to reduce the large investment in precious metals required to manufacture long glass fibers.
The present invention comprises using alloys containing nickel and titanium to make metallic external supports and/or cooling members like cooling tubes, cooling fins connected to heat sinks like cooling fluid manifolds or cooling tubes, cooling manifolds, cooling rings and hollow cooling fins used with fiberizing bushings to make fibers like glass fibers, glassy material fibers and polymer fibers. The invention also includes these metallic cooling members items, and the use of these metallic cooling members in the manufacture of glass fibers and fibers of any other material which requires cooling during the process of forming fibers from the material that is in molten or thermally-softened condition during formation of the fiber.
The nickel-titanium alloys used in this invention contain substantial percentages of nickel and titanium and can contain other materials in small amounts. The compositions of these alloys remain in a martensite crystal structure or phase from room temperature to about 200 degrees F. These alloys are equi-atomic intermetallic alloys that readily form two phases at elevated temperatures above about 200 degrees F., an ordered austenitic phase and a lower temperature martensitic phase. The alloys used in the present invention, if overheated and converted to a harder, more rigid phase, quickly revert to the martensite phase when cooled back below 200 degrees F. These alloys are sufficiently malleable to be bent easily to adjust the metallic cooling members as a tip plate or orifice plate of the bushing sags yet sufficiently rigid to avoid damage during routine operation and maintenance of the bushing. The nickel-titanium alloys used in the present invention have low elastic modulus and low yield strength in the fully annealed condition. Some of the Ni—Ti alloys of interest here have a yield strength in the range of 3,000-5,000 psi and an elastic modulus of 2-5 million psi. These are alloys that are easy to deform and will readily take on a permanent plastic set. These alloys are very desirable for this application. The cost of these alloys is far less than that of precious metal alloys currently being used and far superior to the copper, nickel or nickel and copper alloys currently used in fin-shield type cooling members, both solid and hollow.
The alloys used in this invention are oxidation resistant up to about 800 degrees F. and form a corrosion resistant oxide film that tenaciously bonds to the Ni—Ti alloy and protects the alloy up to about 1500 degrees F. The alloys used in this invention begin to deteriorate and spall above 1500 degrees F.
One family of alloys meeting the above description that are used in the present invention is called NITINOL®), such as 55 NITINOL®, available from the Timet Division of the Titanium Corporation of America located in Toronto, Ohio. This alloy has a composition of about 55 percent nickel, about 45 percent of titanium and minor amounts of iron and nitrogen.
Another family of Ni—Ti alloys for use in the present invention are known as types S, N, C, B, M, and H. These alloys have a nickel content in the range of about 55 and 56 wt. percent, and usually the balance, except for trace amounts, being titanium. Chromium can be present in amounts less than about 0.3 wt. percent. Other similar nickel-titanium alloys are suitable for use in the present invention.
Precious metal bushings are used to make fibers from molten materials like glass, polymers, and glassy materials. A cooling tube type bushing 2 is partially shown in
A plurality of hollow nozzles or tips 12 are formed in or welded to a tip or orifice plate 10 in or around orifices. Normally, the tips 12 are arranged in rows down the length or along the width of the bushing 2. In the bushing 2, the tips 12 are preferably arranged in pairs of staggered rows running along the length of the bushing 2 in a known manner, e.g. as shown in U.S. Pat. Nos. 4,337,075 and 6,196,029 (incorporated herein by reference). The perforated portion 6 of the perforated plate and flange 7 is spaced above the tip plate 10. The tip plate 10 is either a part of the sidewalls 4 or is welded, at the intersection 5 between the tip plate 10 and the end walls and the sidewalls 4 of the bushing 2. Internal supports 9 are welded to the top surface of the tip plate 10 to reduce sagging of the tip plate 10. The internal supports 9 have cutouts 11 above the orifices for the tips 12.
A plurality of cooling tubes 16, made from a nickel-titanium alloy according to the present invention, are spaced below the tip plate 10 and between double rows of tips 12. The cooling tubes 16 have an optional at least one fin 18 on top of the tubes 16 for cooling the tips 12, molten glass flowing from the tips 12 and fibers that are formed at the end of the tips 12 when the bushing 2 is operating. Some of the cooling tubes can have double fins 19 in a known manner such as tubes 20. A ceramic linear support 22 can lay on each tube 20 and extend to the bottom surface of the tip plate 10 in a known manner to provide support for the tip plate 10 in the manner disclosed in U.S. Pat. Nos. 4,356,016 and 6,196,029. Large bushings, having more than 1200 tips 12, use at least one of the double fin cooling tubes 20 and ceramic supports 22. The cooling tubes are supported in a well known manner, such as disclosed in U.S. Pat. No. 5,244,483, incorporated herein by reference.
A side view of the cooling tube 16 is shown in
While the cooling tubes 16 shown in
In operation molten material like glass exits the tips 12 of the bushing 2 and forms a cone-shaped meniscus below each tip. A fiber is pulled away from each meniscus at a very high speed to form a fiber of desired diameter in a well known manner. It is necessary to cool the molten glass meniscus properly to prevent the fibers from breaking and to prevent the molten glass from spreading up the outside of the tips 12 and across the bottom of the tip plate 10 between the tips 12 when the fibers break, an event called flooding of the bushing. Flooding causes the bushing to be taken out of production for extended time while a hot, tedious job of de-flooding the bushing is undertaken.
The surface of the cooling tubes 16 and fins 18, because of their close proximity to the hot tip plate 10, typically over 1100 degrees C., and the hot molten glass, becomes quite hot. Further, these members are exposed to corrosive volatiles coming from the molten glass and to water vapor coming from hot fibers further below the bushing where the fibers are being further cooled by water sprays. These conditions are severe. In addition, because the tip plate 10 sags with time in operation, the cooling tubes 16 and fins 18 must be bent appropriately to maintain the important spacing between the fins 18 and the end of the tips 12. If that spacing is not maintained, the rate of fiber breaks per hour will increase dropping the fiberizing efficiency and the production rate and increasing the manufacturing cost. If the metal tube does not bend easily or quickly, in place, the operator or mechanic will not achieve the best spacing because of the uncomfortable conditions he must work in to do this, or he will damage the cooling member or bushing causing additional lost production and manufacturing costs. Only a few metals have proven suitable to provide the cooling function, the necessary malleability to allow for easy bending or the cooling member while it is in operation to compensate for tip plate sag (affects fiberizing efficiency or fiber breaks/hour) and reasonable cooling member tube life. Those few metals or alloys are all precious metals, or largely precious metals, requiring a substantial capital investment and a corresponding high cost.
In the present invention, at least the cooling tubes 16 are made from nickel-titanium (Ni—Ti) alloys. The fins 18 can also be made from a NiTi alloy. These NiTi alloys contain at least about 98 weight percent nickel plus titanium, preferably at least about 99 weight percent. The NiTi alloys used in this invention can contain other materials in small or trace amounts, such as chromium and/or iron and/or nitrogen. Preferably, the nickel content of the alloy will be in the range of about 55-56 wt. percent. Regardless of the composition, these alloys used in the present invention remain in a martensite structure from room temperature to about 200 degrees F. Also, these alloys, if overheated and converted to a harder, more rigid austenite structure, quickly revert to the martensite structure when cooled back below about 200 degrees F. The alloys used in this invention are sufficiently malleable to be bent easily to adjust the metallic cooling members as a tip plate or orifice plate of the bushing sags yet sufficiently rigid to avoid damage during routine operation and maintenance of the bushing. The cost of these alloys are far less than that of precious metal alloys currently being used and far superior to nickel or copper currently used in fin-shield type cooling members in one or more of the areas of malleabity, life, and resistance to corrosion.
The alloys used in this invention are oxidation resistant up to about 800 degrees F. and form on the surface a thin oxide film that protects the alloy up to about 1500 degrees F. The alloys used in this invention begin to deteriorate and spall above 1500 degrees F.
The cooling assembly 30, the manifolds 32 and fin shields 34, or any part thereof, can be made from the nickel-titanium alloy according to the present invention. Because the manifolds 32 are spaced further from the hot tips 29 and the tip plate 31, it is within the scope of the present invention to use the nickel-titanium alloy only in the fin shields 34. The cooling tube-air tube 36 can also be made from the nickel-titanium alloy, or only the fluid cooling tube 37 or only the air tube 38.
On the interior of each hollow fin 58 are a generally horizontal barrier 70, extending from the manifold wall 57 only a small part of the length of the fin 58, and a plurality of generally vertical, spaced apart separators 72 whose ends are spaced from the top and bottom walls of the fin 58 to form an upper cooling channel 73 and a lower cooling channel 74. The generally vertical separators 72 cause cooling fluid coming from the intake chamber 62 to distribute evenly across the hollow fin 58 and to flow downwardly through generally vertical channels 76 formed by the spaces between the generally vertical separators 72. The generally horizontal barrier 70 can extend to the separator 72 closest to the manifold wall 57, but usually stops a short distance from that separator 70 to allow some cooling fluid to pass between the end of the barrier 70 and that separator 72. The purpose of the barrier 70 is to prevent short circuiting of the cooling fluid and to cooperate with the separators 72 to cause the cooling fluid to be more uniformly distributed over the interior surfaces of the cooling fin 58, directly cooling the hollow fins 58. More details of this cooling assembly 54 and how it is operated in the manufacture of fibers from molten material, and other similar cooling assemblies can be found in U.S. Pat. No. 6,192,714, the disclosure being incorporated herein by reference. This entire cooling assembly, or any part thereof, can be made using a nickel-titanium alloy according to the present invention.
As shown above, the present invention is applicable to cooling apparatus known in the art as cooling tubes and fin shield cooling. Fin shield cooling includes any solid or hollow fin, like element 34 in
Several types of fiberizing bushing cooling apparatus have been shown in detail above, but there are many variations of these and very possibly other metal cooling apparatus that are similarly positioned near a fiberizing bushing. The present invention as described by the following claims is also applicable to those fiberizing bushing cooling means and variations thereof.
