Stock material or miscellaneous articles – All metal or with adjacent metals – Having aperture or cut
Reexamination Certificate
1999-01-11
2001-04-24
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Having aperture or cut
C029S006100, C029S522100, C029S523000, C029SDIG004, C065S492000, C065S493000, C065S495000, C065S374120, C072S370060, C072S700000, C075S252000, C075S255000, C076S107600, C083S030000, C148S024000, C156S293000, C228S056300, C228S193000, C228S196000, C228S197000, C228S224000, C420S466000, C420S467000, C428S598000, C428S637000, C428S670000
Reexamination Certificate
active
06221506
ABSTRACT:
The present invention relates to a method of manufacturing a bushing baseplate, and also to the bushing baseplate obtained thereby and to the bushing itself. The invention also covers brazing filler pastes as novel substances. More particularly, the invention relates to a method of manufacturing a bushing baseplate for drawing glass fibers, to bushing baseplates obtained thereby, and to brazing filler pastes as novel substances.
DESCRIPTION OF THE PRIOR ART
In the manufacture of glass fiber commonly used for reinforcing plastics materials, the bushing is the most critical tool in the production line since it determines the quality of the final product.
The bushing is generally made of an alloy of platinum and rhodium and is in the form of a box into which molten glass is inserted, the box having a baseplate that is perforated by numerous holes. Each of these holes is constituted by a pierced jet known as a “tip” through which the glass flows out to produce a fiber once it has solidified.
In the “direct fusion” bushing technique, the glass is fed in the molten state but, in order to maintain thermal equilibrium, it is necessary to heat the body of the bushing by the Joule effect. The plate constituting the baseplate has several hundred or even several thousand tips, and in bushings already in existence or under development, the number of tips can be as great as 4,000 or even 6,000.
In general, in order to avoid deformation of the baseplate, it is known to distribute mechanical reinforcement over the length thereof and between the locations of the tips, thereby ensuring better stiffness in use.
Present technologies for manufacturing bushings, and in particular for manufacturing bushing baseplates, need to take account of economic constraints associated with fiber production or with drawing from a bushing, and of techniques associated with the geometry and the number of tips per unit area of baseplate through which fibers can be drawn.
A method of manufacturing a bushing baseplate has already been proposed that is based on deforming the entire plate that is to constitute the bushing baseplate by means of a deep-drawing operation.
Unfortunately, a deep-drawing method makes it very difficult to obtain a bushing baseplate of thickness having good regularity.
In the context of a deep-drawing method, it is necessary to leave a sufficient volume of metal between two adjacent holes since otherwise metal taken therefrom during the deep-drawing operation can give rise to weak points in the thickness of the baseplate, and guaranteeing such volumes of metal is very difficult to obtain because of the small spacing.
That technology naturally also prevents to use different materials for the baseplate and for a tip. Deep-drawing technology is also expensive since it requires expensive tooling for deep-drawing purposes, even when deep-drawing is performed area by area. Furthermore, that method lacks flexibility since it is necessary to make a new tool when changing from one model to another.
As a result, the technology has moved to implementing a so-called “associative” manufacturing method which is much more flexible since it consists in fixing tips to a baseplate in which some corresponding number of holes have been formed.
For example, application JP-A-6-218448 published on Aug. 9, 1994 discloses a method in which a certain number of holes are perforated through a bushing baseplate and solid tip-forming cylinders are inserted therein, which cylinders are subsequently flattened or jagged and then perforated.
Similarly, document JP-A-7-81968 published on Mar. 28, 1995, describes inserting hollow tubular elements in the holes of a bushing baseplate, which elements are assembled therein by constituting an interference fit prior to being subjected to diffusion bonding treatment.
Similarly, document JP-A-7-187702, published Jul. 27, 1995, describes a method similar to that of the preceding document, using hollow tubular elements having an outside diameter greater than the inside diameter of the holes in the baseplate.
Proposals are also made in document JP-A-6-171971 published on Jun. 21, 1994 for a method of manufacturing a bushing furnace plate in which, after bushing tips have been inserted in the holes of a baseplate, a spacer element is interposed between each orifice and each tip and is then subjected to diffusion bonding treatment.
The methods of the second category are known as “fitted tip techniques”. The invention forms part of this category technique.
In the prior art of this fitted tip technique, the most widely used bonding method is the method of bonding by diffusion heat treatment. An example of such diffusion heat treatment is given in document U.S. Pat. No. 4,461,191. Prior document JP-A-6-171971 published on Jun. 21, 1994, also performs diffusion bonding.
In the context of diffusion bonding methods, the object is to establish initially, in the hole, intimate contact between a tip and the plate, and then to cause material to diffuse between the tip and the plate during heat treatment at high temperature, the duration and the temperature of the heat treatment being adjusted as a function of the materials being assembled together and as a function of their surface states. The major technical problem with assembled tips is that of obtaining good sealing between each tip and the plate.
An object of the present invention is thus to solve the technical problem consisting in providing a solution in the context of assembled tip techniques that enables good sealing to be obtained between each tip and the plate by limiting or even reducing the number of steps required, while simultaneously making it possible to implement a method that is essentially suitable for full automation.
The invention therefore also needs to solve this problem at low cost, by means of a method that is safe and reliable and which can be used on an industrial scale. The invention makes it possible for the first time to solve this novel technical problem.
Thus, in a first aspect, the present invention provides a method of manufacturing a bushing baseplate, the method comprising making a plurality of holes in a plate that is to constitute the bushing baseplate, inserting at least one tip constituted by a hollow tubular element defining a through duct in each hole in said plate, and bonding the tips to said plate by heat treatment, the method being characterized in that the outside diameter of a tip is slightly smaller than the inside diameter of a hole so as to leave a small amount of clearance after a tip has been inserted in a hole for appropriate positioning, the tip is subjected to mechanical expansion, e.g. by inserting a punch in the duct of the tubular element, thereby mechanically securing the tips and the plate that are to be joined by intimate contact between the walls thereof inside each hole.
In a variant implementation, the heat treatment of bonding of the tips with the plate comprises solid state diffusion.
In another variant implementation, prior to performing heat treatment, continuous lines of a brazing filler paste are positioned between the rows of tips, preferably on the outside of the bushing baseplate, the composition of the paste being adjusted to be liquid at the bonding heat treatment temperature, so that the brazing filler paste, once melted, fills the gaps that may remain between the walls of the tips and the holes in the plate so as to guarantee a good sealing.
In a variant implementation, the above-specified plate is a plate of platinum or platinum alloy.
In another implementation, the tips are made of the same metal or alloy as the plate. The tips may also be made of a metal or alloy that is different from that of the plate.
In another variant implementation, the above-mentioned mechanical expansion consists in performing expansion radially to the axis of the holes in the plate, said axis also essentially coinciding with the axis of the tips in the form of hollow tubular elements.
In a particularly advantageous implementation of the invention, said brazing filler paste comprises a metal or
Guerlet Jean-Paul
Michel Daniel
Pouliquen Franck
Engelhard-CLAL S.A.S.
Jones Deborah
Koehler Robert R.
Nath Gary M.
Nath & Associates
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