MXPA96004581A - Coating for tools in contact with calie glass - Google Patents

Abstract

The present invention relates to a coating resistant to high temperature, intended to be sandwiched between tools and hot glass plates. This comprises a fabric made of an assembly of columns of meshes conferring at least one flat face, the fabric being provided with recesses (C) where the polygonal shape is determined by a plurality of "untied" segments (S3, S4, S5) , S6) each constituted by a portion of a mesh column and of "tied" segments (S1, S2) constituted by the common placement of more than 4 meshes (m) between two columns (A, B) of adjacent meshes , placed in common obtained by reciprocal transfer of meshes (m) from one column to the other

Description

COATING FOR TOOLS IN CONTACT WITH HOT GLASS The invention relates to coatings resistant to high temperature, which contain mainly metal, and more particularly intended to serve as intercalators between hot glass plates and any tool that is brought into contact with them. The invention applies more particularly to coatings for tools used in the hot-treatment installations of sheets or sheets of glass, with a view to making glazing of the annealed, bulged, tempered, enameled type, mainly glazing used in the automotive industry. By "hot" are understood the temperatures that allow the softening of the glass, for example from 600 to 700 ° C, but the invention is not limited to the uses at also high temperatures. As tools capable of being equipped with "interleaved" coatings, it is possible to cite those intended to shape and / or treat the glass sheets as the domed and / or air-hardened shapes, which can be full or annular, or the shapes of conformation adapted to a temper called by contact. It can also be tools for transporting glass plates, mainly conveyor rollers, or any other means of mechanical or pneumatic grip. Any manipulation of a sheet of glass or hot sheet runs the risk of producing its marking, affecting its optical quality. Although the manufacture of glazing requires a high optical quality, which is delicate mainly when it comes to glazing for automobiles where it is also necessary to ensure an excellent definition of the profile or shape, with complex shapes that can lead to more inflection points that need more frequently. a pressing operation of the glass sheet between two complementary bending shapes, of the filled shaped type, associated with an annular shape. To avoid the formation of porosities on the glass, to absorb any dust that will be introduced into the glass / tool interface and, more generally, to preserve the integrity of the surface state of the glass sheets, it is thus known to provide the tools of a reversal called intercalar, adapted to be able to give the leaves a flexible and soft contact. This coating must also have sufficient hot mechanical durability, a certain deformability to be able to adapt to complex tool shapes, but also adequate air permeability, especially if it must be coated with a hardening tool, as well as a thermal conductivity too high A coating that meets all these requirements is already known from European Patent EP-B-0,312,439: it consists of a metal fabric with thermal conductivity of less than 3W.pf .K ", and which is made up of wicks or cables made of A plurality of at least 90 elementary threads with a diameter of less than 50 microns, and organized together to form meshes The aim of the invention is to propose an improvement to this type of metallic coating, mainly in order to obtain a coating that reduces even the risks of marking and / or having increased durability The aim of the invention is a coating resistant to high temperature, intended to be sandwiched between tools and hot glass plates.This coating comprises a fabric made of an assembly of columns of meshes , which confer at least one flat face.The fabric is also provided with holes where the polygonal shape is d determined by a plurality of "unattached" segments, each constituted by a portion of a column of meshes, and of "joined" segments constituted by the common placement of more than four meshes between two columns of adjacent meshes, this placement being in common obtained by the reciprocal transfer of meshes from one column to the other. For a fabric with two flat opposite sides, this common placement can be mainly more than two meshes of two columns of adjacent meshes. According to the invention, "mesh" is understood as an elementary wire loop connected to other loops to form the segments of the fabric. It is understood by "hollow" the free space delimited by said segments. By "fabrics" is meant both the meshes of collected meshes and the fabrics of stretched meshes. In the context of the invention, this term also encompasses tissues, grids, grid backings and braids. (It should be noted that in the case of the mesh fabrics collected, it is "rows" of meshes rather than "columns" of meshes). It is also understood by "reciprocal transfer of meshes" the fact by which a union is created between two columns of meshes, so that the thread of a given column of meshes, comes to be inserted in the adjacent column to form thus at least one mesh and because, reciprocally, the thread of this last column is inserted into the first to form at least one mesh. At least two meshes "put together" between the columns have been made in the sense of the invention. Similarly, fabric is understood to have at least one "flat face", a fabric where all the columns of meshes of at least one and the same face are flat. The coating as defined above has many advantages. The fact that it is a fabric gives it a certain extension capacity in all directions, which allows it to be used to coat tools with complex shapes, for example with pronounced curvature. The texture of the fabric makes it sufficiently absorbent to the powders. The conferring on this fabric a flat face also allows to avoid any marking of the glass sheets because it offers a very smooth contact. The fact that the two opposite sides of the fabric present this characteristic, allows us to use it without having to distinguish a "front" face and a "back" face. However, in certain less demanding applications and, mainly for ease of operation, can be limited to a fabric that has a single flat face. By choosing the size and geometry of the gaps in the fabric, the permeability ratio of the coating can be precisely regulated, which is important if it is intended to equip air quenching forms. Finally, the fabric presents a good resistance to mechanical wear. Indeed, the holes mentioned above have a strong cohesion, which means that it has at least two meshes in the "bound or tied" segments, which are the result of the interaction between two columns of meshes, which means that if any Once any of the meshes "in common" should be broken at the time of prolonged use, there will be at least one second "common" mesh. This avoids any risk of brutal local rupture of the coating, causing a direct point contact between the tool and the hot glass, and then a marking of the latter. These gaps according to the invention can then be of very different shapes. In this way, they can be symmetrical, having mainly joined segments all of the same length, and segments not equally joined all of the same length. But these can also be non-symmetrical, with the joined and unbonded segments of different lengths. The structure of the fabric according to the invention thus offers numerous possibilities for better adapting the coating to its final use. They can for example adopt holes in a hexagonal shape that create an alveolar aspect, or even a honeycomb. In addition, the size and / or shape of the recesses can vary over the entire fabric, creating interlacing zones of different appearance and properties in the fabric. It is possible to have an advantage in adopting, for example, a differentiated permeability in the fabric, distinguishing mainly between the peripheral zone and the central zone, when this is intended to cover a flat shape.

However, a gap size is chosen such that they have a perimeter of between 8 and 80 millimeters, preferably between 20 and 40 millimeters. In the structure of the fabric, these gaps have a certain capacity for deformation, but their perimeter remains globally constant. Advantageously, the meshes are woven from the spun yarn, simple or composite. This type of threads is obtained for example from a continuous cable of elementary threads, which suffer a mechanical breakage in such a way that it breaks into discontinuous, short rows of random length, followed by the breaking of one or more twists (thread simple yarn), then eventually a twist to fix the twists (compound yarn). Any other type of spinning operation that leads to a similar result can be used, mainly the so-called "air jet" spinning. This type of yarn is interesting to use, primarily because although it is metallic, its thermal conductivity is relatively low, which is rather favorable in the case where the glass undergoes a thermal treatment and / or is susceptible to present a slightly different temperature than that of the tool. In addition, the fact that it is composed of discontinuous fibers, improves the "softness" of the fabric and gives it a great flexibility in its thickness. Lastly, the spun yarn lends itself particularly well to the weaving operation thanks to its flexibility. In fact, the discontinuous fibers give the spun yarn a particular appearance, with the so-called marginal fibers where one end is imprisoned by twisting the yarn and then the other end protrudes, which makes it possible to optimally distribute the weight of the sheet of yarn. glass over the whole fabric. Everything concurs then, with such a thread, to preserve the optical quality of the glass. The yarn that is woven can be unique, mainly presenting a metric number comprised between 1 and 30, preferably between 1.5 and 10, when this is made of metal of the steel type (the metric number indicates the length of the yarn, necessary, in meters, to obtain a mass of 1 gram). When the yarn is not made of steel, but of ceramic or other metal material for example, these values of the metric number are weighted according to the ratio of the densities between the metal and the material in question, in order that The apparent diameter of the yarn is comparable. In this way, for a thread where the elementary fibers will be 4 times less dense than the metal of the steel type, the limit values of the metric number indicated above, will be multiplied by 4. It is also possible to weave a set of several of these threads, mainly of 2 to 5 threads, not imposing the assembly necessarily a twisting operation. Preferably, the yarn from which the fabric is made is made up of at least 90 elementary fibers, each elementary fiber having a diameter of less than 50 micrometers, and mainly comprised between 8 and 20 micrometers. In fact, the two parameters that are on the one hand the number of elementary fibers of each thread, and on the other hand the number of threads assembled, allow to vary as desired the thickness of the thread that will be effectively woven, and then, at the end , the thickness of the fabric. A third parameter may also be involved, which is the number of twists that the yarn has suffered before its weaving.

We will now refer more precisely to the type of material constituting the fabric according to the invention: it must be resistant to high temperature, which is the reason why it is advantageous to choose a fabric comprising metallic threads. This can be on the other hand mainly, if not entirely, consisting of metal wires. However, heat-resistant non-metallic wires, more particularly based on ceramic material, can also be incorporated into the fabric, in addition to these metal wires., of silicon carbide, of polyimide or of aromatic polyimide as the polymer known under the trade name KEVLAR. As seen above, these threads, which are either metallic or not, can be a result of the meeting of a certain number of elementary threads. Another variant consists in the fabric comprising "hybrid" yarns, that is to say yarns containing a mixture of metallic elementary fibers and non-metallic elementary fibers, of the ceramic type, silicon carbide, polyimide or aromatic polyamide. The elementary threads or fibers of the fabric, which are metallic, are advantageously chosen based on stainless steel, mainly of type 3161. A preferred embodiment consists in choosing an essentially austenitic steel. The steel comprises, for example, a proportion by mass of chromium of at least 17%, mainly comprised between 17% and 19%, and a proportion of nickel of at least 12%, mainly comprised between 13% and 14%, always maintaining a proportion in mass on carbon, less than or equal to 0.03%. This type of steel has in fact a very good resistance to oxidation at high temperature, a very high mechanical durability, which guarantees the coating a long life. Preferably, the thickness of the coating is chosen to be less than 5 millimeters, mainly between 1 and 3 millimeters. Its thermal conductivity is usually less than 3 W.m '.K "1, p inciply from 0.1 to 0.2 .m' .K" '. Its air permeability can be regulated, as we have seen above, to different values. This is mainly at least 2 m / s. The permeability is here defined by the number of cubic meters capable of traversing in a second the equivalent of one square meter of material, when the pressure difference on one side and on the other side of the latter is 200 Pa (Pascal). The measurement of air permeability is conducted following the specifications of the NF EN ISO 9237 standards from a test surface of 20 cm '. When such a coating is used to coat hardening tools, it may be advantageous to have a more significant air permeability; in this case, this is mainly at least 5 m / s, and preferably at least 7 m / s, in cubic meters of air capable of traversing the equivalent of one square meter of material, when the difference in pressure by one part and on the other side of the latter is 200 Pa (Pascal), from a test surface of 20 cm. "According to a variant, the two sides of the fabric may have the same structure, the same appearance, but They are differentiated by the nature of the threads that constitute them, in this way, we can distinguish the face destined to be "next to the glass", made of threads of material specifically optimized to avoid marking, and the face destined to be "together to the tool "which can consist of threads of a different material (or a mixture of materials), mainly less expensive.

According to another variant, in the case where the two faces of the fabric are flat, they can be advantageously identical among them, which eliminates any risk of error at the moment in which the fabric is placed on the tool. In order to obtain fabrics that present two flat faces in this way, technical weaving differences, known in the textile industry, must be taken into account. One of these consists of resorting to a weaving machine called double-bedding: that is, a machine with two rows of needles that weave in parallel, thus creating the meshes that constitute two flat outer "layers". The weaving machine is also preferably chosen in order to manufacture a fabric - of thrown meshes, of the Rachel machine type. This type of machine authorizes in effect a very large choice of fabric dimensions, mainly as regards its width. It is thus possible to obtain fabrics in the form of narrow strips which are fully adapted to serve as coatings to the annular shapes of bulging and / or tempering. This type of machine also allows to directly manufacture tubular fabrics, usable to cover conveyor rollers, mainly.

As described above, the invention also relates to the application of the coating described above to the coating of tools for glass plates, in the course of their thermal treatment of the annealed, domed, air-tempered or contact type, tools mainly of the type formed full or domed frames and / or temple. This also refers to the application of the coating for the coating of support elements and / or transport of hot glass plates, such as conveyor rollers, conveyor belt, any means of mechanical or pneumatic grip, mainly by suction. Other details and advantageous features of the invention will emerge from the following description of the different, non-limiting embodiments of the coating, with the help of the attached figures which represent: - figure 1: a developed representation of two portions of columns of adjacent meshes of a fabric according to the invention, which have two flat opposed faces, - figure 2: the same portions of columns of the fabric, seen from the front, the face being hidden back, - figures 3 and 4: two variants of the shape of holes in the fabric, - figure 5: an enlarged schematic view of a hole according to figure 3, - figure 6: a developed representation of two portions of columns of meshes adjacent, of a fabric according to the invention having a flat face.

All these figures are extremely schematic. These represent different variants of a fabric according to the invention. In all of the following examples, the fabric is of cast meshes and uses mainly austenitic stainless steel yarns, which have a mass proportion of chromium of 18%, a proportion by mass of nickel of 13% and a proportion of mass of carbon lower than 0.03%. The threads are made up of two twisted yarns, each with a respective metric number. 11 meters per gram, spun yarns consisting of approximately 100 base filaments, with an apparent diameter of 12 micrometers. In the example corresponding to figures 1 to 5, the weaving is carried out with the help of a machine called Rachel double-gauge 9 gauge (the caliber is the number of needles placed over a distance of one inch). In the example corresponding to figure 6, the weaving is carried out with the help of a machine of the Rachel type of simple napkin. If reference is made to Figure 1, two columns A, B of adjacent meshes of a fabric according to the invention are observed in an expanded manner. Each column consists of rows "n" that have two meshes (or loops) "" of thread. It is observed according to figure 1, that which is called "row" is a set of two adjacent meshes (loops) of the same column of meshes, each one being placed on one of the faces of the fabric. To create the gaps in the fabric, these two columns of meshes are made to interact locally and in a regular manner over their entire length in the following way: an It thread coming from the column of meshes B that is to be inserted in the column of meshes A. Reciprocally, a thread I2 coming from the column of meshes 2 comes to be inserted in the column of meshes B.

The thread I creates a row "b" in the column A, and the thread I. creates a row "a" in the column B. This transfer of threads thus creates a bond between the two columns. As shown in Figure 1, it is observed that the four ties are thus created next, with a double transfer of two rows from one column to the other. The assembly of meshes "put together" by these reciprocal transfers about the two columns and constitutes a "tied" segment in the sense of the invention, which will allow to obtain the holes C of varying shape and size. This is schematized in Figure 2, where it is observed that the 4 ties or unions created between columns A and B form a tied segment consisting of 6 rows in total, ie 12 meshes. It is then sufficient to choose the number of meshes placed so in common, and the number of meshes not placed in common, between two columns. For clarity, this principle is schematically represented in figure 5: the crosses symbolize the common placement of a certain number of meshes between two columns: each gap C is then, in this representation, delimited by two tied segments s :, ys ? and for four untied segments s, s < , s * and s., in order to obtain a globally hexagonal form. Figures 3 and 4, even more schematically, represent two types of gaps C: in figure 3, there is a symmetrical hexagonal shape with two joined segments Si, S: longitudinally, comprising for example 6 rows in common, and four unbonded segments s1 (s «, s * and s * of equal length and comprising, for example, 2 rows In figure 4, the gaps are this time not symmetrical, even in a hexagonal form, but with two segments joined s;, s, - of the same length as two rows in common, two segments not joined to s., s < of the same length, each comprising two rows and two unattached segments s *, s «of The same length, each comprising 4 rows, is also possible in numerous variants: the recesses can thus, for example, be in the form of a rhombus, mainly when the length of the joined or tied segments is very small in relation to the length of the segments not joined, the tissue obtained by means of double fonts it has two identical and very flat opposite sides globally, which is excellent on the plane of optical quality: columns of approximately "square" section mesh are in fact made and where two opposite sides constitute tissue tails. It is possible to insert between the two "layers" of meshes that constitute the outer faces of the fabric, at least one additional thread in order to create a three-dimensional structure where the thickness and flexibility can be controlled by nature, number and length of the threads that meet the two layers of meshes. Figure 6 shows, in an expanded manner, two columns (A, B) of adjacent meshes of another fabric according to the invention, which has a single flat face. Unlike the previous example, each row "n" has a "m" wire mesh. The interaction of two columns (A, B) of meshes is done in the same way as in the previous example. Through the reciprocal transfers, six meshes (m) placed in common between the two columns (A, B) are obtained. The ways in which a thread of a column is inserted into the adjacent column can be very diverse. In the case of figure 1, it has been seen that thread 1 creates a row "b" in column A, then "returns" to its starting column B. In addition, only one "m" mesh can be created . It is evident that the invention is not limited to this embodiment: it is also very possible that this thread I, once inserted in the column A, "remains" to create there several rows (or several meshes) then in this column . In addition, it is not mandatory that he "returns" to column B, and can also go immediately to insert in the column (not shown) that is on the other side of column A. In conclusion, the fabrics that fall within the scope of the invention are provided with recesses "c" where the polygonal shape is determined by a plurality of "unattached" segments each constituted by a portion of columns of meshes and segments "tied or united "constituted by the common placement of at least two meshes" m "between two adjacent columns of meshes (A, B). -the tissues that have a flat face have tied or joined segments, constituted by the common placement of two meshes, four, six or more. -the fabrics that have two flat faces, have joined or tied segments constituted by the common placement of more than four meshes, mainly 8 or 12. 10 i c,

Claims (25)

1. A coating resistant to high temperature, intended to be sandwiched between tools and hot glass plates, characterized the coating because it comprises a fabric made of an assembly of columns of meshes that give the fabric at least one flat face, the fabric being provided with hollows where the polygonal shape is determined by a plurality of "unbonded or tied" segments, each constituted by a portion of a column of meshes and segments • tied or joined "constituted by the common placement of more than four meshes between two columns of adjacent meshes, placed in common, obtained by reciprocal transfer of meshes from one column to the other.

2. The coating according to claim 1, characterized in that the fabric, mainly obtained by a double-needle weaving machine, has two flat opposed faces.

3. The coating in accordance with the rei indication 1, characterized in that the fabric, mainly obtained by a simple knitting machine, has a flat face.

4. The coating according to claim 1, characterized in that the fabric comprises metallic threads.

5. The coating according to claim 4, characterized in that the fabric comprises, of course, non-metallic yarns, of the type of ceramic fibers, silicon carbide fibers, polyamide fibers or aromatic polyamide fibers.

6. The coating according to any of claims 1 to 5, characterized in that the fabric comprises "hybrid" yarns containing a mixture of metallic and non-metallic elementary fibers of the ceramic, silicon carbide, polyimide or aromatic polyamide type. .

7. The coating according to any of the preceding claims, characterized in that at least a part of the metallic elementary threads or fibers of the fabric is based on stainless steel, mainly of type 316L, preferably essentially austenitic.

8. The coating according to claim 7, characterized in that the stainless steel comprises a proportion by mass of chromium of at least 17%, mainly comprised between 17% and 19%, and a proportion by mass of nickel of at least 12%, mainly comprised between 13% and 14%, and preferably a mass proportion of carbon less than or equal to 0.03%.

9. The coating according to any of the preceding claims, characterized in that the recesses have a symmetrical shape, mainly with "tied" segments all of the same length and "untied" segments all of the same length.

10. The coating according to any of claims 1 to 8, characterized in that the recesses have a non-symmetrical shape with the "tied" and "untied" segments of different lengths.

11. The coating according to any of the preceding claims, characterized in that the segments that determine the shape of the holes are constituted by more than two meshes, mainly from 2 to 10 meshes, preferably from 2 to 6 meshes.

12. The coating according to any of the preceding claims, characterized in that the recesses have a hexagonal shape.

13. The coating according to any of the preceding claims, characterized in that the size and / or the shape of the voids vary (n) on the assembly of the fabric, creating woven areas of different appearance and properties in the fabric.

14. The covering according to any of the preceding claims, characterized in that the recesses have a perimeter comprised between 8 millimeters and 80 millimeters, mainly between 20 and 40 millimeters.

15. The coating according to any of the preceding claims, characterized in that the fabric meshes are made of stretched meshes.

16. The coating according to any of the preceding claims, characterized in that the meshes are woven from spun, simple or composite yarn.

17. The coating according to any of the preceding claims, characterized in that the meshes are woven either from a single yarn, mainly from a metric number comprised between 1 and 30, for example comprised between 1.5 and 10, when this is metallic, or of a montage of several of these threads, mainly 2 to 5 threads.

18. The coating according to any of the preceding claims, characterized in that the yarns from which the fabric is made, are composed of at least 90 elementary fibers, each elementary fiber having a diameter of less than 50 microns, and preferably comprised between 8 and 20 microns.

19. The coating according to any of the preceding claims, characterized in that the thickness of the fabric is less than 5 millimeters, mainly comprised between 1 and 3 millimeters.

20. The coating according to any of the preceding claims, characterized in that the fabric has a thermal conductivity of less than 3 W. pf'.K "', mainly comprised between 0.1 and 0.2 W.m" .K "'.

21. The coating according to any of the preceding claims, characterized in that the fabric has an air permeability of at least 2 m / s according to the NF EN ISO 9237 standard.

22. The coating according to any of the preceding claims, characterized in that the fabric has two faces that are distinguished by the nature of the threads that constitute them.

23. The coating according to claim 2, characterized in that the fabric has two identical faces.

24. The application of the coating according to any of the preceding claims for the coating of tools for glass plates in the course of their thermal treatments of the annealed, domed, air-tempered or contact type, as well as the flat or square shapes of domed and / or tempering.

25. The application of the coating according to any of claims 1 to 21, the coating of support elements and / or transport of hot glass plates, such as conveyor rollers, conveyor belts, either by means of mechanical or pneumatic prehension , mainly by aspiration.