GB1571100A - Method of manufacturing reinforced rubber or plastics belts or bands - Google Patents

Description

(54) METHOD OF MANUFACTURING REINFORCED RUBBER OR PLASTICS BELTS OR BANDS (71) We, SGHIESSER AG, of Schafferhauserstrasse 316, Zurich, Switzerland, a joint stock company organised under the laws of Switzerland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- The present invention relates to a method of manufaoturing bands, especially conveyor bands or belts, formed od rubber or other plastics masses containing reinforcement inserts.

For conveyor bands or belts formed of rubber or other plastics materials, such as PVC a complicated fabrication operation has been required to obtain the desired strength in both the lengthwise and the transverse directions and also the desired load-carrying capability.

According to the heretofore proposed fabrication methods there are employed for re inforcement purposes narrowly woven fabrics formed of cotton or synthetic fibers and, if desired, also steel wire, and the following procedures are carried out.

The fabrics (in the case of very wide conveyor bands or belts, for instance of 2000 mm width, sometimes 12 or mere fabric plies are used and for narrow conveyor bands, for instance of 400 to 1000 mm width, on the average 4 to 8 fabric plies) are initially freed of moisture by drying dn special drying cabinets or chambers.

Thereafter, these fabric plies are either moved through a tank containing an adhesive solution, in order to realize a good connection between the fabric and the rubber layer or they are coated on a coating machine with an adhesive or bonding layer formed of rubber cement. Since both sides or faces must be coated, it is often necessary to move the fabric through the coating machine two or more times. The solvent is either lost, or must be reclaimed by the use of expensive special equipment.

In order to obtain a good connection between the fabric and the rubber or between one fabric layer and the next fabric layer, extremely expensive bonding agents must be added to the solution or the rubber layers.

Following such operations, the fabric travels through a calender containing at least three rollers, in order to apply a thin rubber layer to the fabric, which then provides the connection for Ithe next fabric. This operation is known as frictioning. Since (this rubber layer must be present at both sides, the fabric also in this case generally must travel through the machine twice, or there must be available a very expen isive calender having four rollers.

The thus prepared fabric is wound up together with a specially prepared fabric-follower fabric-to avoid sticking upon rolls in as long as possible pieces and in this condition is available for further working. In order to avoid any pre-vulcanization of the rubber layers, especially in the summer season in heated rooms, the work must be carried out relatively quickly, since if prevulcanization does occur good interconnection or bonding is no longer possible.

The individual fabric webs are now assembled together into a package and move through a calendar having two rolls (the so-called doubler), there thus being formed a package of fabric reinforcement, the so-called sandwich.

In a separate operation, the cover layers (upper and lower cover layers of rubber or plastics stored with an intermediate cloth to prevent sticking together) are connected to either side of the sandwich of fabric reinforced ment by calendering. To prevent penetration of water, air, or contaminants such as sand, there are laterally applied either extruded strips or strips cut from sheets. Thereafter vulcanization is effected either in molds (longitudinal molds of 5 to 20 meters length) or a through-pass-vulcanization machine having large heated rolls and a counter-pressure band formed of steel or rubber, the so-called Auma or "Rotecure" Trade Mark).

In the case of very wide bands, forwmstance of 2000 mm width or more, which must also be produced in very large piece lengths, a layer is inserted between the fabric layers, this layer being provided in the lengthwise direction with steel cables or wires of a 4 to 12 mm diameter.

The fabrication of these steel cord layers is very complicated and only possible with expensive installations, so that such special bands can usually be fabricated only by large, financially sound companies. These steel cord layers are likewise produced upon the calender, and it is absolutely necessary to work with a large, very expensive calender having four rolls which requires both a considerable amount of work and expenditure in energy.

The thicker the cable the more difficult the operation. With a wire cable of only 06 mm diameter there are considerable difficulties in disposing rubber or other plastics material completely between and about the cables. The wire cables must be highly tensioned at the calender, from both the front and the rear, so that the incoming rubber material cannot shift the wire cables. These wire cables are normally embedded at a center-to-center spacing of 10 to 15 mm.

Where layers are joined at the calender it is impossible to avoid completely the inclusion of air bubbles. The same is also true during doubling of the fabric layers. With wire cables there is usually also entrained moisture (condensate), which, during vulcanization at temperatures of 1500 or more, can convert into vapor and thus form pockets. The steel cables are thus usually dried prior to entering the calender.

The greatest problem with rubber conveyor bands, produced in this manner for the last decades, resides in the fact that such air/or moisture pockets can migrate due to the movement of the travelling band and can split the individual layers longitudinally. The conveyor band is thus markedly weakened and can become defective after only a relatively short period of use. The same defect can arise following damage to the conveyor band by mechanical action. Large stones or rocks can tear a hole in the conveyor band, which may then be torn in the lengthwise direction, sometimes for hundreds of meters of its length if, for instance, it becomes caught at a transverse strut or support.

If air or moisture is present between the fabric layers, due to the production technique, or if air, water or sand penetrates between the fabric layers at a later time due to a mechanical defect, then it is merely a matter of time until individual fabris layers are torn and the band must be exchanged, since even if repair of the defective location is made, air, water or sand can still be left in the band and tbe destruction action begins anew due to movement of the band.

This is especially so because the rubber layers are separated internally by the fabric threads which are devoid of rubber, and thus at this location air or moisture can collect during repair work, and too little rubber is present between the fabric layers for sand granules to be completely embedded in the rub ber without cutting the fabric or tearing the fabric layer.

Since during frictioning the fabric at the calender or the production of the steel cord layers at the calender there is practically only line contact where the calender rolls touch, the pressure build-up at this location is relatively small so that the material is not sufficiently pressed into the fabric or the intermediate spaces between the wire cables to give the necessary intimate connection, and the pressingout of air and moisture is not complete.

It is moreover also extremely difficult to maintain all of the steel cables at exactly the same tension over the entire width of the work area at the calender (sometimes amounting to more than 2000 mm) so that the conveyor band can be weakened or travel crooked.

The problem of air inclusion and irregular tensioning of the individual wires is likewise a very great problem during the fabrication of steel cord layers for the tire industry (radial tires). The hereinafter described fabrication method is applicable to the production of such raw or blank layers and for steel cord layers for the tire industry.

The present invention provides a method of fabricating a composite band of reinforced rubber or plastics material which comprises the steps of extruding a first band of rubber or plastics material about reinforcement material, extruding at least one second band of rubber or plastics material about reinforcement material, cutting the second reinforced band(s) transversely into pieces at intervals substantially equal to the width of the first reinforced band, placing the pieces upon at least one side of the first reinforced band with their cut edges extending longitudinally of the first reinforced band, and uniting the resulting assembly under pressure to form the composite reinforced band.

This method has the following advantages compared to the conventional procedure: (a) considerably less handling and working operations; (b) simpler, smaller and less expensive plant; (c) little inclusion of air or water; (d) lower energy requirement; (e) a conveyor band of comparable strength can be of thinner and lighter construction, permitting also use with a lighter conveyor frame or support; (f) the coherent block of rubber or other plastics material with embedded reinforcement will not readily separate into individual layers, or split longitudinally when damaged by large stones; (g) increased longevity of the product; (h) product uniformity and simple repair; (i) it is possible to employ cords or cables of natural or synthetic fibers or monofilaments instead of steel.Steel cables can, with difficulty, ;be coated at the calender with rubber, but conventional cables or cords of natural or synthetic fibers or monofilaments cannot since, even when exposed to small pressures during calendering, they are pressed into an oval configuration resulting in enormous difficulties both from the standpoint of strength and with respect to uniform travel of the band.

The invention can thus provide a product of improved quality with savings in materials and production time and plant.

The method of the present invention can utilize fabrics of open mesh instead of the previously employed fabrics of absolutely closed mesh. There is thus produced a compact band in which the reinforcement materials are completely embedded without any inolusions, and in which tearing apart of the layers of reinforcement is not normally possible.

Stones which have penetrated composite bands produced according to the invention are worked towards the outside by the movement of the rubber, or locally encapsulated in the rubber.

Instead of up to 20 individual layers as in conventional bands, 2 to 6 layers are sufficient for composite bands made according to the invention.

During extrusion (round head or wide nozzle head) the reinforcement is contacted by the rubber and, due to the large pressure build-up in the injection head (a multiple of the pressure during calendering), the plastic or rubber material penetrates into each depression and tightly encloses the reinforcement. Air or gaseous media, such as water vapor, are displaced rearwardly by capillary action.

Thus, it is possible to employ cables of practically unlimited cross-sectional size and, in contrast to calendering, the cross-section always remains round. There may thus be formed a strip with embedded cord or cable which is limited in length only by the length of the latter.

Like or different reinforced lengthwise extruded strip is cut into lengths equal to the width of the first strip, and the resulting pieces turned through 900 and placed from one or both sides upon the first strip containing the lengthwise cords. It is possible to employ in the top or bottom pieces thinner cords, and for to stack on top of one another a number of layers. The layers are then united under pressure, e.g. as was previously the case they are vulcanized or pressed together in a mold or press or subjected to throughpass- vulcanization with for instance the Auma or "Rotocure" equipment, or vulcanized with microwaves.

Since air or water which has laterally penetrated can again escape by capability acion, it is not even necessary to apply at the side a cover as a protection. When the cut pieces are applied to both sides of the first strip, the reinforcement is either the upper or lower layer of pieces can suitably be fabric d open (e.g.

square or rectangular) mesh, provide the loadcarrying capacity and lateral reinforcement.

It is possible to employ two or more strips having lengthwise directed cords, or it is possible to simply use stronger cords.

It is equally possible to construct uppermost pieces having Itransverse extending cords such that the spacing between the individual cords or cables is somewhat greater than normal. In this instance, a stone which has penetrated, if it then strikes against an obstruction, is held back by the next following cord and pushed out of the hole.

For the formation of endless conveyor bands the use of cables of natural or synthetic fibers or monofilaments means that, in contrast to steel cables, welding is not required, rather the cables projecting at one end are simply inserted into connection locations at the other end, where deposited rubber, during vulcanization, intensively bonds with the cables and thus provides a good connection.

It is possible to employ steel cord for the lengthwise reinforcement, but it is practically impossible to utilize the steel cord for the transverse reinforcement (turned 90" to the lengthwise direction), since during cutting of the thick steel cables the individual wires immediately spread apart. Therefore, it is necessary either to weld each individual wire prior to cutting (which involves a tremendous amount of work and a large amount of waste), or initially to cut the pieces which are to be transversely placed to be much longer and after vulcanization to cut them to the exact width (also associated with a tremendous amount of waste and work). A lateral protection then must be subsequently provided by vulcanization during a separate working step.

The invention will be better understood from consideration of the following detailed description of specific embodiments which is given by way of example only. This description makes reference to the annexed drawings wherein: Figures 1 and 2 illustrate bands produced according to prior art techniques; and Figure 3 is a cross-sectional view of a band produced according to the present invention.

In Figs. 1 and 2 the bands consist essentially of a core formed by a fabric package 1 which, if desired, can additionally be reinforced by steel wires 2. This core 1 is provided at its top surface and lower surface with a cover layer 3 and a bottom layer 4, respectively.

Additionally, there is provided a lateral protective layer 5 which, if desired, can be formed of one piece with the cover layer 3 or bottom layer 4, for instance as shown for the lateral pntective later 5' of Figure 2.

Now in Figure 3 of the drawing there is shown, in contrast to the foregoing prior art bands, part of band 6 produced according to the present invention. The core layer 7 is provided with lengthwise extending reinforcement cables 8. The cover layer 9 and the bottom or lower layer 10 each have transversely extending reinforcements 11 and 12 in the form of the illustrated cables or the like. The cover layer 9 and the bottom layer 10 are formed of a multiplicity of individual plates which are mutually vulcanized with the core layer 7.

WHAT WE CLAIM IS: 1. A method of fabricating a composite band of reinforced rubber or plastics material which comprises the steps of extruding a first band of rubber or plastics material about reinforcement material, extruding at least one second band of rubber or plastics material about re inforcement material, cutting the second reinforced band(s) transversely into pIeces at intervals substantially equal to the width of the first reinforced band, placing the pieces upon at least one side of the first reinforced band with their cut edges extending longitudinally of the first reinforced band, and uniting the resulting assembly under pressure to form the composite reinforced band.

2. A method according to claim 1 wherein the assembly is vulcanized.

3. A method according to claim 1 wherein the assembly is welded together.

4. A method according to any preceding claim wherein at least one of the bands is formed by extruding a wider strip and then cutting it longitudinally to the required band width.

5. A method according to any preceding claim wherein such cut pieces are applied to both faces of the first band.

6. A method according to any preceding claim wherein the first and second bands are formed separately.

7. A method according to any preceding claim wherein the first and second bands have different reinforcement.

8. A method according to claim 1 substantially as hereinbefore described.

9. A composite band produced by a method according to any preceding claim.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. the present invention. The core layer 7 is provided with lengthwise extending reinforcement cables 8. The cover layer 9 and the bottom or lower layer 10 each have transversely extending reinforcements 11 and 12 in the form of the illustrated cables or the like. The cover layer 9 and the bottom layer 10 are formed of a multiplicity of individual plates which are mutually vulcanized with the core layer 7. WHAT WE CLAIM IS:

1. A method of fabricating a composite band of reinforced rubber or plastics material which comprises the steps of extruding a first band of rubber or plastics material about reinforcement material, extruding at least one second band of rubber or plastics material about re inforcement material, cutting the second reinforced band(s) transversely into pIeces at intervals substantially equal to the width of the first reinforced band, placing the pieces upon at least one side of the first reinforced band with their cut edges extending longitudinally of the first reinforced band, and uniting the resulting assembly under pressure to form the composite reinforced band.

2. A method according to claim 1 wherein the assembly is vulcanized.

3. A method according to claim 1 wherein the assembly is welded together.

4. A method according to any preceding claim wherein at least one of the bands is formed by extruding a wider strip and then cutting it longitudinally to the required band width.

5. A method according to any preceding claim wherein such cut pieces are applied to both faces of the first band.

6. A method according to any preceding claim wherein the first and second bands are formed separately.

7. A method according to any preceding claim wherein the first and second bands have different reinforcement.

8. A method according to claim 1 substantially as hereinbefore described.

9. A composite band produced by a method according to any preceding claim.