|Title of Invention||
"LINING RESISTANT TO HIGH TEMPERATURE"
|Abstract||The subject of the invention is a covering resistant to high temperature and intended to be inser-ted between tools and plates of hot glass. It comprises a knitted fabric formed from an assembly of stitch wales giving at least one plane face, the knitted fabric being provided with openings (C) , the polygonal shape of which is determined by a plurality of "non-bound" segments (s3, s4, s5, s6) , each consisting of a portion of a stitch wale, and of "bound" segments (s:, s2) formed by making more than 4 stitches (m) common to two adjacent stitch wales (A, B) , the making common being obtained by the mutual transfer of stitches (m) from one wale to the other.|
|Full Text||The present invention relates to the lining resistant to
high temperature, especially containing metal, and
intended particularly for serving as inserts between
plates of hot glass and any tool coming into contact
The invention applies more particularly to coverings for tools used in installations for the hot treatment of glass sheets for the purpose of producing glazings of the annealed, bulged, tempered and enamelled type, especially the glazings used in the motor vehicle industry. By "hot", therefore, are to be understood temperatures making it possible to soften the glass, for example from 600 to 700°C, but the invention is not limited to uses at temperatures as high as this. Tools which are capable of being equipped with "insert" coverings and which may therefore be mentioned are those intended for shaping and/or treating the glass sheets, such as bulging and/or air-tempering moulds, which may be solid or annular, or shaping moulds suitable for so-called contact tempering. They may also be tools for transporting the glass plates, especially conveyor rollers, or any other means of mechanical or pneumatic gripping.
Any handling of a hot glass sheet risks marking
it and affecting its optical quality. Now the manufac-
ture of glazings necessitates a high optical quality,
which presents problems especially with regard to
glazings for motor vehicles, where it is also necessary
to ensure excellent definition of the outline, together
with complex shapes which may comprise a plurality of
deflection points usually requiring an operation to
press the glass sheet between two complementary bulging
moulds of the solid-mould type associated wi£h an
To avoid the formation of pits in the -glass, to absorb possible dust which may infiltrate at the glass/tool interface or, more generally, to preserve
The intactness of the surface state of the glass sheets, it is therefore known to provide the tools with a suitable so-called insert covering which can ensure that the sheets have flexible and soft contact. More-over, this covering must possess sufficient mechanical durability under hot conditions, some deformability so as to be capable of matching complex tool shapes, but also adequate air permeability, especially if it is to cover tempering tools, as well as a thermal conduc-tivity which is not too high.
A covering meeting all these requirements is
already known from the patent EP-B-0,3l2,439: this consists of a metallic fabric which-Has""a~'t'Tie"rmaT conductivity below 3W.m~ . K" and which is formed from tufts consisting of a plurality of at least 90 elementary threads of a diameter smaller than 50 microns, the said tufts being organized together to form stitches.
The object of the invention is to propose an improvement to this type of metallic covering, espe-cially in order to obtain a covering which further reduces the risks of marking and/or which has increased durability.
The subject of the invention is a covering resistant to high temperature and intended to be inserted between tools and plates of hot glass. This covering comprises a knitted fabric formed from an assembly of stitch wales giving at least one plane face. The knitted fabric is provided, furthermore, with openings, the polygonal shape, of which is determined by a plurality of "non-bound" segments, each consisting of a portion of a stitch wale, and of "bound" segments formed by making more than four stitches common to two adjacent stitch wales, this making common being obtained by the mutual transfer of stitches from one wale to the other. For a knitted fabric having two plane opposite: faces, this making common can especially involve more than two stitches from two adjacent stitch wales.
According to the invention, by "stitch" is understood an elementary thread loop connected to the other loops to form the segments of the knitted fabric.
By "opening" is understood the free space delimited by the said segments.
By "knitted fabric" are understood both tuck-stitch knits and cast-stitch knits. Within the context of the invention, this term also embraces cloths, net-tings, cane plaitings and braids. (It should be noted that, as regards tuck-stitch knits, stitch "rows" is referred to rather than stitch "wales").
It is also understood by "mutual transfer of stitches" that a connection is made between two stitch wales, in such a way that the thread of a given stitch wale is inserted into the adjacent wale to form at least one stitch there, and that, conversely, the thread of the latter wale is inserted into the first wale to form at least one stitch there. There are, therefore, at least two stitches "made common" to the wales within the meaning of the invention. Likewise, by a knitted fabric with at least one "plane face" is meant a knitted fabric, of which all the stitch wales of at least the same face are plane.
The covering, as defined above, has many advantages. The fact that it is a knitted fabric gives it some extensibility in all directions, thus allowing it to be used for covering tools of complex shapes, for example having a pronounced curvature. The texture of the knitted fabric makes it sufficiently absorbent to dust. Moreover, giving this knitted fabric a plane face makes it possible to avoid any marking of the glass sheets, since it offers very smooth contact. The fact that the two opposite faces of the knitted fabric advantageously have this characteristic makes it pos-sible to use it without any longer having to distin-guish between a "right" face and a "wrong" face. How-ever, in some less demanding uses and especially for practical convenience, it is possible to employ only a knitted fabric having a single plane face. By selecting
the size and geometry of the openings in the knitted fabric, the permeability coefficient of the covering can be set accurately, this being important if it is intended for equipping air-tempering moulds.
Finally, the knitted fabric has high resistance to mechanical wear. In fact, the abovementioned openings have strong cohesion, in that there are at least two stitches in the "bound" segments which are a result of the interaction between two stitch wales, and this means that, if one of these "common" stitches were ever to break in the event of prolonged use, at least one second "common" stitch would remain. This avoids any risk of an abrupt local rupture of the covering, giving rise to direct point contact between the tool and hot glass and consequently to marking of the latter.
These openings according to the invention can therefore have highly diverse shapes. Thus, they can be symmetrical, in particular having bound segments all of the same length and non-bound segments likewise all of the same length. However, they can just as easily be asymmetric, with bound and non-bound segments of dif-ferent lengths. The structure of the knitted fabric according to the invention therefore affords numerous possibilities for adapting the covering as closely as possible to its ultimate use. It is possible, for example, to adopt openings having a hexagonal shape, creating a cellular or even honeycomb appearance.
Moreover, the size arid/or shape of the openings may vary over the knitted fabric as a whole, thus pro-ducing in the knitted fabric knitting zones of differ-ent appearance and properties. In fact, it may be advantageous to adopt, for example, a differentiated permeability in the knitted fabric, in particular by distinguishing between a peripheral zone and a central zone, when it is intended for covering a solid mould.
Usually, however, a size of openings is selec-ted such that they have a perimeter of between 8 and 80 millimetres, preferably between 20 and
40 millimetres. As a consequence of the structure of the knitted fabric, these openings have some deforma-bility, but their perimeter remains substantially con-stant .
Advantageously, the stitches are knitted from single or composite spun thread. This type of thread is obtained, for example, from a continuous sliver of ele-mentary threads which undergoes mechanical cracking so as to break it into short discontinuous fibres of ran-dom length, cracking being followed by one or more twists (single spun thread) and then, if appropriate, by doubling to fix the said twists (composite spun thread). Any other type of spinning operation termina-ting in a similar result can be used, in particular so-called "air-jet" spinning.
This type of thread is appropriate to use, first because, although metallic, its thermal conduc-tivity is relatively low, this being somewhat advanta-geous if the glass undergoes thermal treatment and/or is capable of having a temperature slightly different from that of the tool. Furthermore, the fact that it consists of discontinuous fibres improves the "softness" of the knitted fabric and gives it high flexibility in terms of thickness. Lastly, the spun thread is particularly suitable for the knitting opera-tion on account of its flexibility. In fact, the dis-continuous fibres give the spun thread a particular appearance, with so-called marginal fibres, one end of which is wedged by twisting in the thread and the other end of which projects, thus making it possible, in par-ticular, to distribute the weight of the glass sheet over the knitted fabric as a whole in the best possible way. Everything about such a thread thus assists in preserving the optical quality of the glass.
The thread which is knitted may be single, in particular having a metric count of between 1 and 30, in particular between 1.5 and 10, when it is made of metal of the steel type (the metric count indicates the thread length necessary, in metres, to obtain a mass of
1 gram) . If the thread is not made of steel, but, for example, of ceramic material or of another metal, these metric count values have to be weighted as a function of the ratio of the densities between the metal and the material in question, so that the apparent diameter of the thread is comparable. Thus, for a thread, the ele mentary fibres of which are four times less dense than metal of the steel type, the above-indicated limit values of the metric count would have to be multiplied by four.
An assembly of a plurality of these threads, especially 2 to 5 threads, can also be knitted, this assembly not necessarily requiring a doubling operation.
Preferably, the thread from which the knitted fabric is made consists of at least 90 elementary fibres, each elementary fibre having a diameter smaller than 50 micrometres, in particular between 8 and 20 micrometres.
In fact, the two parameters, which are, on the one hand, the number of elementary fibres of each thread and, on the other hand, the number of assembled threads, make it possible to vary, as desired, the thread size which would actually be knitted and there fore, ultimately, the thickness of the knitted fabric. A third parameter, which is the number of twists which the thread has undergone before it is knitted, can also have an effect.
Referring now more specifically to the type of material forming the knitted fabric according to the invention, it must be resistant to high temperature, which is why a knitted fabric comprising metallic threads can advantageously be selected. Moreover, it can consist mainly or even completely of metallic threads. However, it is also possible to incorporate in the knitted fabric, in addition to these metallic threads, heat-resistant non-metallic threads, in par-ticular based on ceramic material, silicon carbide, polyimide or aromatic polyamide, such as the polymer
known by the tradename KEVLAR. As seen above, these threads, whether metallic or not, can result from the combination of a particular number of elementary threads.
In another alternative, the knitted fabric com-prises "hybrid" threads, that is to say threads con-taining a mixture of metallic elementary fibres and of non-metallic elementary fibres of the ceramic, silicon carbide, polyimide or aromatic polyamide type.
The threads or elementary fibres of the knitted fabric which are metallic are advantageously selected as being based on stainless steel, especially of the type 316L. A preferred embodiment involves selecting an essentially austenitic steel. The steel comprises, for example, a content by mass of chromium of at least 17%, especially between 17% and 19%, and a content of nickel of at least 12%, especially between 13% and 14%, whilst preserving a content by mass of carbon less than or equal to 0.03%. This type of steel has, in fact, very good resistance to oxidation at high temperature and very high mechanical durability, this ensuring that the covering has an extended lifetime.
Preferably, the thickness of the covering is selected as less than 5 mm, especially between 1 and 3 mm. Its thermal conductivity conventionally remains below 3 W.m^.K"1, especially 0.1 to 0.2 W.m-1.K-1. As seen above, its air permeability can be set at various values. It is, in particular, at least 2 m/s. Perme-ability is defined, here, by the number of cubic metres capable of passing in one second through the equivalent of one square metre of the material when the pressure difference on either side of the latter is 200 Pa (Pascal). The measurement of air permeability is con-ducted according to the specifications of the standard NF EN ISO 9237 on the basis of a test area of 20 cm2.
When such a covering is used for covering tem-pering tools, it may be advantageous to have a higher air permeability; in this case, this is, in particular, at least 5 m/s and preferably at least 7 m/s in terms
f cubic metres of air capable of passing through the equivalent of one square metre of the material when the pressure difference on either side of the latter is 200 Pa (Pascal), on the basis of a test area of 20 cm2.
According to one alternative, the two faces of the knitted fabric can have the same structure and the same appearance, but differ from one another in the nature of the threads which form them. Thus, a distinc-tion can be made between the face intended to be the "glass side", made from threads of material specifi-cally optimized to avoid marking, and the face intended to be the "tool side", which can consist of threads of a different, in particular less costly, material (or mixture of materials).
According to another alternative, if the two faces of the knitted fabric are plane, they can also advantageously be identical to one another, thus elimi-nating any risk of error when the said knitted fabric is fastened to the tool.
To obtain knitted fabrics thus having two plane faces, various knitting techniques known from the tex-tile industry can be considered. One of them involves using a so-called double-section knitting machine: that is to say, a machine with two rows of needles knitting in parallel, thus producing the stitches which form two plane outer "laps". Moreover, the knitting machine is preferably selected so as to manufacture a cast-stitch knit, of the Raschel machine type. In fact, this type of machine allows a very wide choice of dimensions of knitted fabric, especially as regard its width. Knitted fabrics in the form of narrow bands can be obtained in this way, this being perfectly suitable for serving as coverings for annular bulging and/or tempering moulds. This type of machine also makes it possible to manufacture directly tubular knitted fabrics which can be used, in particular, for covering conveyor rollers.
As mentioned above, the invention also relates to the use of the above-described covering for covering tools for glass plates during their thermal treatment
of the annealed, bulging, air-tempering or contact-tempering type, the said tools being especially of the type comprising solid moulds or bulging and/or tempering frames. It also relates to the use of the covering for covering elements for supporting and/or transporting plates of hot glass, such as conveyor rollers, a conveyor belt, any means of mechanical or pneumatic gripping, especially by suction.
The present invention relates to a lining resistant to high temperatures, designed to be inserted between equipment and hot glass plates, characterized in that said lining comprises a knitted fabric incorporating metallic fibres, formed by an assembly of stitch columns, or in the case of weft knitted fabrics, formed by rows of stitches, giving said knitted fabric at least one planar face, the knitted fabric being provided with openings (C), of which the polygonal shape is determined by a plurality of "unlinked" segments (33, 84, ss, se), each constituted by a portion of stitch column and "linked" segments (si, sa) constituted by the bringing together of two to four stitches (m) between two columns (A, B) or rows of adjacent stitches, the said bringing together obtained by a reciprocal transfer of stitches (m) from one column to the other.
Other details and advantageous characteristics of the invention will emerge from the following description of various non-limiting embodiments of the covering by means of the accompanying figures in which:
• Figure 1 shows an exploded representation of two por
tions of adjacent stitch wales of a knitted fabric
according to the invention having two plane opposite
• Figure 2 shows the same portions of wales of the
knitted fabric, seen from the front, the rear face
• Figures 3 and 4 show two alternative shapes of
openings in the knitted fabric,
• Figure 5 shows an enlarged diagrammatic view of an
opening according to Figure 3,
• Figure 6 shows an exploded representation of two por-
tions of adjacent stitch wales of a knitted fabric
according to the invention having one plane face.
All these figures are highly diagrammatic. They represent different versions of a knitted fabric accor-ding to the invention.
In all the following examples, the knitted fab-ric is of the cast-stitch type and uses threads made of mainly austenitic stainless steel, comprising a content by mass of chromium of 18%, a content by mass of nickel of 13% and a content by mass of carbon less than 0.03%.
The threads consist of two doubled spun threads having a respective metric count of 11 metres per gram, the said spun threads consisting of approximately 100 basic filaments of an apparent diameter of 12 micrometres. In the example corresponding to Figures
1 to 5, knitting is carried out by means of a so-called double-section Raschel machine of gauge 9 (the gauge is the number of needles arranged over a distance of 1 inch). In the example corresponding to Figure 6, knitting is carried out by means of a machine of the single-section Raschel type.
Referring to Figure 1, this shows in exploded form two adjacent stitch wales A, B of a knitted fabric according to the invention. Each wale consists of rows "n" comprising two thread stitches (or loops) "m" . It can be seen from the figure that what is referred to as a "row" is a set of two adjacent stitches (loops) of the same stitch wale, each being arranged on one of the faces of the knitted fabric. To create openings in the knitted fabric, these two stitch wales are made to interact locally and uniformly over their entire length in the following way: a thread l1coming from the stitch wale B is inserted into the stitch wale A. Conversely, a thread 12 coming from the stitch wale A is inserted into the stitch wale B.
The thread lx produces a row "b" in the wale A, and the thread 12 produces a row "a" in the wale B. This transfer of threads thus forms a tie between the two wales. As shown in Figure 1, it can be seen that 4 ties are thus formed in succession, hence with a double transfer of two rows from one wale to the other. The set of the stitches "made common" by these mutual transfers brings the two wales closer together and forms a segment, "bound" within the meaning of the invention, which will make it possible to obtain open-ings C of variable shape and size. This is represented diagrammatically in Figure 2, which shows that the 4 ties produced between the wales A and B form a bound segment consisting altogether of 6 rows, i-e 12 stitches. It is then sufficient to select the number of stitches thus made common and the number of stitches not made common to two wales. For greater clarity, this principle is represented diagrammatically in Figure 5: the crosses depict making a particular number of
stitches common to two wales: in this representation, therefore, each opening C is delimited by two bound segments s1 and s2 and by four non-bound segments s3, s4, s5 and ss, so as to obtain a substantially hexagonal shape.
Figure 3 and 4 show two types of openings C even more diagrammatically: Figure 3 has, once again, a symmetrical hexagonal pattern with two bound segments sx, s2 of the same length, comprising, for example, 6 rows in common, and four non-bound segments s3, s4, s5, s6 of the same length and comprising, for example, 2 rows. In Figure 4, the openings are this time asym-metric, again of hexagonal shape, but with two bound segments sx, s2 of the same length and comprising 2 rows in common, two non-bound segments s3, s4 of the same length and each comprising 2 rows, and two non-bound segments s5, s6 of the same length and each comprising 4 rows .
Many alternatives are, of course, possible: for example, the openings can be diamond-shaped, especially when the length of the bound segments is very small in relation to the length of the non-bound segments.
The fabric obtained by double-section knitting has substantially two identical and highly plane oppo-site faces, this being excellent in terms of optical quality: in fact, there are stitch wales which have an approximately "square" cross-section and two opposite faces of which form those of the knitted fabric.
It is possible to insert at least one addi-tional thread between the two "laps" of stitches form-ing the outer faces of the knitted fabric, in order to produce a three-dimensional structure, the thickness and flexibility of which can be controlled by the nature, number and length of the threads joining the two laps of stitches.
Figure 6 shows in exploded form two adjacent stitch wales (A, B) of another knitted fabric with one plane face according to the invention. In contrast to the preceding example, each row "n" comprises one
thread stitch "m". The interaction of two stitch wales (A, B) takes place in the same way as in the preceding example. By virtue of the mutual transfers, six stitches (m) made common to the two wales (A, B) are obtained.
The ways in which a thread of one wale is in-serted into the adjacent wale may differ widely. With regard to Figure 1, it was seen that the thread l1 pro-duces a row "b" in the wale A and then "returns" to its initial wale B. It would be perfectly possible for it to produce only one stitch "m" there.
It goes without saying that the invention is not limited to this embodiment: it is quite possible for this thread 11; once inserted into the wale A, to "remain" there:, so as to produce a plurality of rows (or a plurality of stitches) in succession in this wale. Moreover, it is not obligatory for it to "return" to its wale B, and it can just as easily be inserted subsequently into the wale (not shown) which is on the other side of the wale A.
As a conclusion, the knitten fabrics which are in the framework of the invention, are provided with openings (C) , the polygonal shape of which is determined by a plurality of « non-bound » segments each consisting of a portion of a stitch wale, and of «bound » segments formed by making at least two stitches (m) common to two adjacent stitch wales (A,B) :
The knitten fabrics with one plane face have bound segments formed by the making common of two, four, six or more stitches.
- The knitten fabrics with two plane faces have bound segments formed by the making common of four stitches, notably eight or twelve.
1. Lining resistant to high temperatures, designed to be inserted
between equipment and hot glass plates, characterized in that said lining
comprises a knitted fabric incorporating metallic fibres, formed by an
assembly of stitch columns, or in the case of weft knitted fabrics, formed
by rows of stitches, giving said knitted fabric at least one planar face, the
knitted fabric being provided with openings (C), of which the polygonal
shape is determined by a plurality of "unlinked" segments (33, 84, ss, SG),
each constituted by a portion of stitch column and "linked" segments (si,
82) constituted by the bringing together of two to four stitches (m)
between two columns (A, B) or rows of adjacent stitches, the said
bringing together obtained by a reciprocal transfer of stitches (m) from
one column to the other.
2. Lining as claimed in claim 1, wherein the knitted fabric, more
particularly obtained by a double needle-bed knitting machine, has two
opposite, planar faces.
3. Lining resistant to high temperatures as claimed in claim 1,
wherein the knitted fabric, more particularly obtained by a single needle-
bed knitting machine, has one planar face.
4. Lining resistant to high temperatures as claimed in claim 1,
wherein the knitted fabric incorporates metallic yarns.
5. Lining resistant to high temperatures as claimed in claim 4,
wherein the knitted fabric also comprises non-metallic yarns such as
ceramic fibres, silicon carbide fibres, polyimide fibres or aromatic
6. Lining resistant to high temperatures as claimed in one of claims
1 to 5, wherein the knitted fabric comprises "hybrid" yams containing a
mixture of elementary, metallic and non-metallic fibres which can be
ceramic, silicon carbide, polyimide or aromatic polyamide.
7. Lining resistant to high temperatures as claimed in one of the
preceding claims, wherein at least one part of the metallic yarns or
elementary fibres of the knitted fabric is based on stainless steel, in
particular of type 316L, and preferably essentially austenitic.
8. Lining resistant to high temperatures as claimed in claim 7,
wherein the stainless steel has a chromium weight content of at least
17%, particularly between 17 and 19%,
and a nickel weight content of at least 12%, particularly between 13 and 14%, and preferably a carbon weight content equal to or below 0.03%.
9. Lining resistant to high temperatures as claimed in claim 1,
wherein the openings have a symmetrical shape with in particular
"linked" segments all having the same length and "unlinked" segments
all having the same length.
10. Lining resistant to high temperatures as claimed in one of the
claims 1 to 8, wherein the openings have an asymmetrical shape with
"linked" and "unlinked" segments of different lengths.
11. Lining resistant to high temperatures as claimed in as claimed in
claim 9, wherein the segments determining the shape of the openings are
constituted by more than 2, particularly 2 to 10 and preferably 2 to 6
12. Lining resistant to high temperatures as claimed as claimed in
claim 1, wherein the openings have a hexagonal shape.
13. Lining resistant to high temperatures as claimed in claim 1,
wherein the size and/or shape of the openings vary over the entire
knitted fabric, creating in the latter knitting zones having different
appearances and properties.
14. Lining resistant to high temperatures as claimed as claimed in
claim 1, wherein the openings have a perimeter between 8 and 80mm,
particularly between 20 and 40 mm.
15 Lining resistant to high temperatures as claimed in as claimed in claim 1, wherein the stitches of the knitted fabric are warp knitted stitches.
16. Lining resistant to high temperatures as claimed in as claimed in
claim 1, wherein the stitches are knitted from a single or folded spun
17. Lining resistant to high temperatures as claimed in as claimed in
claim 1, wherein the stitches are knitted either from a single yarn,
particularly of metric count between 1 and 30, e.g. between 1.5 and 10
when it is metallic, or an assembly of several such yarns, particularly 2
to 5 yarns.
18. Lining resistant to high temperatures as claimed in as claimed in
claim 4, wherein the yarns from which the knitted fabric is made are
constituted by at least 90 elementary fibres, each elementary fibre more
particularly having a diameter below 50 micrometers and preferably
between 8 and 20 micrometers.
19. Lining resistant to high temperatures as claimed in as claimed in
claim 2, wherein the thickness of the knitted fabric is below 5 mm,
particularly between 1 and 3 mm.
20. Lining resistant to high temperatures as claimed in claimed in
claim 2, wherein the knitted fabric has a thermal conductivity below
-i.K-1, particularly between 0.1 and
21. Lining resistant to high temperatures as claimed in claimed in
claim 2, wherein the knitted fabric has an air-permeability of at least 2
m/s in accordance with NF Standard EN ISO 9237.
22. Lining resistant to high temperatures as claimed in claim 2,
wherein the knitted fabric has two faces differing by the nature of the
yarns forming them.
23. Lining resistant to high temperatures as claimed in claim 2,
wherein the knitted fabric has two identical faces.
|Indian Patent Application Number||426/DEL/2000|
|PG Journal Number||13/2009|
|Date of Filing||11-Apr-2000|
|Name of Patentee||N.V. BEKAERT S.A.,|
|Applicant Address||BEKAERT STRAAT 2-B-8550 ZWEVEGEN, BELGIUM.|
|PCT International Classification Number||D03D 17/00|
|PCT International Application Number||N/A|
|PCT International Filing date|