EP0962565B1 - Conveyor belt for high temperature objects - Google Patents

Description

The present invention relates to a conveyor belt intended to be mounted in a high temperature object conveying installation in particular glass objects brought to temperatures up to up to 800 or 900 ° C.

In the glass industry, during the manufacturing process, glass objects brought to temperatures up to 800 or 900 ° C are transported by textile belt conveyors. These conveyor belts which are stretched and supported by rollers must on the one hand withstand the inherent tensile and bending forces to the mechanical conveying system and on the other hand resist the temperature of glass objects without causing a surface defect these.

Conveyor belts used in general consisted of asbestos fibers whose characteristics mechanical and thermal allowed to fulfill the conditions mentioned above in a satisfactory manner.

However, we know that asbestos is toxic and that it is now prohibited from use. No other fiber has the same mechanical and thermal characteristics as those shown by asbestos. It is therefore not possible to obtain a band textile conveyor meeting the same specifications as above by simple substitution of the asbestos fibers by another fiber.

Document DE-A-38 43 811 describes a multi-layer woven conveyor belt, consisting of aramid yarns mixed with other synthetic yarns. Said band is suitable for transporting objects at high temperature.

The applicant's goal is to offer a tape textile asbestos-free conveyor which can both withstand the tensile and bending forces inherent in the system mechanics of commonly used conveyors that can transport objects at high temperatures, without risk of marking including glass.

This goal is perfectly achieved by the textile conveyor belt of the invention which consists of at least two layers, namely a outer layer intended to be in contact with objects and a layer internal intended to be in contact with the mechanical system of conveying. Typically according to the invention, the cohesion of the layers being provided by bonding threads, the outer layer and the threads of binding are formed of threads composed of fibers, in intimate mixture, on the one hand in stainless steel and on the other hand in a material chosen from those which, brought to high temperature, decompose into carbon; of the more the inner layer is formed of threads having good properties to the both mechanical resistance and thermal resistance.

Depending on the particular structure of the conveyor belt the invention, it is the inner layer which must mainly ensure the mechanical resistance to the entire conveyor belt, while it is the outer layer which must be able to withstand the very high temperature at least in the outer face which is in contact with the transported objects. Stainless steel fibers need to be mixed, in intimate mixture, with other fibers to be able to be spun under acceptable conditions. In addition, the presence in the outer layer and in the fiber bonding threads which, brought to high temperature, decompose into carbon allows to have a state of surface, in cooperation with stainless steel fibers, which do not do not mark objects worn at high temperature, particular of glass objects. So the contact of objects with high temperature with the surface portion of the outer layer and the wires bonding causes the decomposition of fibers other than stainless steel carbon. This decomposition which has the advantage of obtaining a surface condition not causing marking does not cause of unacceptable disadvantage insofar as the son of the layer external and the binding threads, in this surface portion, are not subjected to particular mechanical forces since these forces are supported mainly by the inner layer of the strip conveyor.

Preferably, the fibers, in intimate mixture with the steel stainless, which break down into carbon are para-aramid fibers, in particular those known under the names Kevlar, Twaron, or polybenzimidazole fibers known as designation P.B.I., Zylon.

Preferably, the constituent wires of the outer layer and the wires of binding consist of a mixture of 50 to 90% by weight of fibers of stainless steel and 10 to 50% by weight of decomposing fibers high temperature carbon.

Preferably the constituent wires of the inner layer are made from para-aramid fibers.

Advantageously, to increase the dimensional stability of the conveyor belt facing the mechanical constraints of the conveying, the outer layer and the inner layer are reinforced by a frame, for example the constituent wires of one and / or the other layer, in warp and weft being a fabric, are reinforced by a metallic continuous filament or any other high resistance filament mechanical and thermal.

In a preferred embodiment, the conveyor belt the invention is obtained by a multiply weaving comprising at least two folds corresponding respectively to the outer layer and to the inner layer.

In this embodiment, preferably the strip conveyor has four plies, the two outer plies being made up, with the binding threads, of an intimate mixture of steel fibers stainless and aramid fibers, while the two inner plies are formed from threads obtained from aramid fibers.

Preferably, in this latter configuration, the four folds are reinforced, in warp and weft, by a continuous filament of reinforcement either metallic or in a high resistance material mechanical and thermal.

The present invention will be better understood on reading the description which will be given of a preferred embodiment of a four-ply high temperature object conveyor belt, illustrated by the attached drawing in which the single figure is a representation very schematically in longitudinal section of said strip.

The conveyor belt 1 is a textile belt obtained by the traditional multi-ply weaving technique. It comprises four successive folds 2,3,4,5 (that is to say four superimposed fabrics) whose cohesion is achieved by means of binding threads 6, 7. Each fold 2,3,4,5 is formed by warp threads 8 and by weft threads 9. The superposition of the four folds is blocked by the binding threads which pass alternately from the upper face 2 to the first fold 2 up to the lower face 5b of the fourth fold 5. The crossing of the binding threads 6, 7 takes place in the zones located between the successive weft threads 9.

The textile strip 1, as illustrated in the figure, has a structure perfectly symmetrical from one face to the other. However in the application targeted by the invention, namely a conveyor belt high temperature objects, the composition of the different plies and threads can be distinguished according to whether the folds are intended to be turned to the mechanical conveying system or are intended to support high temperature objects.

More precisely, the objects brought to high temperature are intended to come into contact with the upper face 2 a of the first fold 2, while the lower face 5 b of the fourth fold 5 is intended to be in contact with the tensioning rollers and drive system.

Under these conditions, the chain son 8 constituting the first ply are threads obtained from an intimate mixture of steel fibers stainless and para-aramid fibers, at a blend of 70% by weight of 316L 12microns stainless steel fibers and 30% para-aramid fibers such as Kevlar or Twaron. Preferably, the wires of the weft constituting the first ply are also obtained from a intimate blend of stainless steel fibers and para-aramid fibers so that no surface appears on the surface of the strip 1 wire not containing stainless steel.

The warp threads and the weft threads of the fourth fold 5 are consisting of threads obtained from para-aramid fibers of the type Kevlar.

The binding threads 6, 7 are, for their part, obtained from a intimate blend of stainless steel fibers and para-aramid fibers Kevlar type, 50 to 90% of stainless steel fibers and 10 to 50% Kevlar fibers.

In a specific embodiment, the second fold 3 had the same composition as the first fold 2, while the third fold 4 had the same composition as the fourth fold 5.

This is the surface portion of the first ply 2 and the bonding son 6, 7 from the level of the surface 2 a of the first ply 2 which are in contact with high-temperature objects, which must have the highest thermal resistance . The para-aramid fibers, which make it possible to obtain a suitable spinning of the stainless steel fibers, in intimate mixture with them, have the characteristic of decomposing in the form of carbon at temperatures of the order of 800 or 900 ° C. This decomposition is in no way prohibitive, on the contrary since it gives the surface portion of the conveyor belt 1, a surface condition which does not cause any marking on the objects brought to high temperature, in particular glass objects. This decomposition, which can cause a certain loss of mechanical strength, is not troublesome from this point of view since the mechanical strength of the conveyor belt 1 is mainly conferred by the third and fourth plies which are made of son formed of fibers of para-aramid, well known for their very high mechanical resistance.

The present invention is not limited to the preferred mode of realization which has just been described by way of non-exhaustive example. In particular it is possible to use other fibers than para-aramid fibers for the constitution of the outer layer, i.e. the first fold, namely in particular polybenzimidazole fibers, which like the polyaramid fibers break down into carbon when they are brought to high temperature.

It is understood that the further the inner layer is from the outer layer, and less required thermal resistance properties for this inner layer are important. In the case illustrated above, the inner layer formed by the fourth fold 5, is insulated thermally by the superposition of the other three folds 2,3,4.

If necessary, it is possible to increase the stability of the strip by reinforcing it with a reinforcement. Through example the warp and weft threads constituting all or part of the layers can be reinforced with continuous metallic filaments or other filaments with high mechanical and thermal resistance.

In the example described above, the composition of the third and fourth son forming the inner layer differs from that of the first and second wire forming the outer layer. This solution presents a definite advantage in terms of cost price, due to the higher cost stainless steel fibers. However, nothing technically prevents to use, for the inner layer, threads made from a mixture intimate of stainless steel fibers and para-aramid fibers. Interest could in particular consist in the manufacture of a strip perfectly symmetrical both in structure and composition and having therefore not a reverse side and a right side.

Claims (8)

1. A textile conveyor belt constituted by at least two layers, namely an outer layer designed to come into contact with articles and an inner layer designed to come into contact with the mechanical conveyor system, the cohesion between the layers (2, 3, 4, 5) being provided by binding threads (6, 7), the belt being characterised in that the outer layer (2, 3) and the binding threads (6, 7) are made of threads that are made up of an intimate mixture of fibers comprising both stainless steel fibers and fibers of a material selected from those which decompose into carbon when raised to high temperature, and in that the inner layer (4, 5) is made of threads having good properties concerning both mechanical strength and resistance to temperature.
2. A conveyor belt according to claim 1, characterised in that the fibers intimately mixed with the stainless steel and that decompose into carbon are para-aramid fibers or indeed polybenzimidazole fibers.
3. A conveyor belt according to claim 1 or 2, characterised in that the threads constituting the outer layer and the binding threads are constituted by a mixture comprising 50% to 90% by weight stainless steel fibers and 10% to 50% by weight fibers that decompose into carbon at high temperature.
4. A conveyor belt according to one of claims 1 to 3, characterised in that the threads constituting the inner layer are made from para-aramid fibers.
5. A conveyor belt according to one of claims 1 to 4, characterised in that the threads constituting the outer layer and/or the inner layer are reinforced by continuous metal filaments or other filaments having high mechanical strength and high resistance to temperature.
6. A conveyor belt according to one of claims 1 to 5, characterised in that it is obtained by multi-ply weaving comprising at least two plies corresponding respectively to the outer layer and to the inner layer.
7. A belt according to claim 6, characterised in that it comprises four plies. two outer plies (2, 3) being constituted, as are the binding threads (6, 7) by an intimate mixture of stainless steel fibers and of aramid fibers, while the third and fourth plies (4, 5) are made of threads obtained from aramid fibers.
8. A belt according to claim 7, characterised in that the warp threads and the weft threads of the four plies (2, 3, 4, 5) are reinforced by continuous filaments of metal or of some other material having high mechanical strength and resistance to temperature.

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