For the purpose of conveying loose materials such as bulk materials, that is, rock/stones, mineral resources, excavation material, agricultural products, et cetera, use has long been made of troughed conveyor belts, which receive the conveyable material at a receiving location on their carrying side and discharge the same at a discharge location. Since the conveyable material is open to the environment as it is being transported, contaminants and environmental weathering influences can act on the conveyable material, and the latter can pollute the environment and also pose a risk to the environment. It is also the case, on account of their configuration, that troughed conveyor belts can be used to realize curves and gradients only to a limited extent. It is thus not usually possible, in conventional belt systems, to exceed an angle of inclination of 20° in gradient. If this is the limit of feasibility, it is necessary to connect a plurality of inter alia specific conveying belts with transfer locations. This increases the complexity for, and therefore the costs of, the conveyor system to a considerable extent.
In order to eliminate these disadvantages, conveyor belts which are closed during operation and are referred to as tube belts, tubular conveyor belts, pipe belts or mega pipes, were developed in the 1980s. The tube belts are rolled together between the receiving location and discharge location to give a closed tube, by virtue of the outer belt flanks overlapping and thus fully enclosing the conveyable material. This means that the conveyable material in the tube belt and the environment are completely separated from one another, since the tube belt remains closed over the conveying route. It is only for the purposes of receiving and discharging the transportable material that a tube belt widens and assumes the form of a conventional troughed conveyor belt. This rules out contamination of the bulk material along the conveying route and the associated environmental pollution. It is also the case that the conveyable material cannot be influenced by the environment during transportation. Further essential advantages of the tube belts in relation to the conventional troughed conveyor belts reside in the possibility of realizing very narrow three-dimensional curves and in the relatively high angles of inclination of up to 35° in gradient, which means that complicated three-dimensional curved routes can be realized by a single system. Since tube belts usually have a smooth surface on their carrying side, the angles of inclination are nevertheless limited to a gradient of up to 35°, depending on the bulk material properties.
In order to eliminate these disadvantages, conveyor belts which are closed during operation and are known as SICON®conveyor belts or pocket (conveyor) belts have also been developed. A pocket conveyor belt comprises two textile-reinforced profiles each with a steel cable vulcanized therein as a tension member. The profiles run over the sets of rollers and carry the pocket which accommodates the conveyable material. This droplet-shaped pocket consists of highly flexible rubber and is connected to the profiles by means of hot vulcanization. The profiles are arranged one above the other during transportation, and the belt is therefore closed off in a dust-tight manner. The belt is carried, and guided, by specific sets of rollers which, for the closed state of the belt, comprise a carrying roller and a guide roller. Further sets of rollers, each comprising a carrying roller and one to three guide rollers, are available for loading and unloading the belt and for curves and gradients.
In a manner similar to tube belts, the essential advantages of the pocket conveyor belt in relation to the conventional troughed conveyor belts reside in the possibilities of realizing very narrow three-dimensional curves and in the relatively high angles of inclination of up to 35°; in the case of conventional belt systems, the angle of inclination cannot usually exceed 20°. This makes it possible to realize complicated three-dimensional curved routes by a single system, without any transfer locations on the conveying route. In addition, the material in the pocket conveyor belt and the environment are completely separated from one another, since the pocket conveyor belt remains closed over the conveying route. For loading purposes, the pocket conveyor belt is opened with the aid of a specific set of rollers for opening and closing the belt. The belt can be unloaded at an overhead discharge point or an S-shaped discharge station. At the S-shaped discharge station, it is possible optionally for the belt to be emptied or for the conveyable material to be poured into the belt again.
A pocket conveyor belt differs from the conventional tube belt not just in construction, but also in functioning and areas of application. It is thus possible for a pocket conveyor belt, depending on the profile size, to negotiate radii of 0.6 m or 1.0 m, which cannot be realized by a conventional tube belt. The minimum curve radius which can be realized by a tube belt is approximately 30 m. In contrast to the tube belt, the conveyor length, the conveyor cross section and the associated conveyor capacity and maximum possible material particle size of a pocket conveyor belt are very limited. All of this predestines a pocket conveyor belt for an “in-plant closed” transport of industrial bulk materials, while a tube belt is considered in practice to be more akin to an “out-plant closed” conveying principle for the entire range of particle sizes.
For a number of application cases, the advantages of the tube belts or the pocket conveyor belts and the steep conveyor belts are required at the same time, that is, a tube belt or pocket conveyor belt which can be used even at angles of inclination above 35°.
U.S. Pat. No. 6,170,646, GB 1197700, U.S. Pat. No. 5,351,810, JP 480 48 385 U, JP 580 83 314 U, United States patent application publication 2012/0000751 A1, FR 14 968 97 A, GB 88 76 98 A, JP 582 16 803 A, U.S. Pat. No. 3,392,817 A and WO2005/085101 A1 disclose a number of technical solutions in this respect for increasing the angle of inclination of tube belts and pocket belts by differently shaped profiles having been applied to the carrying-side cover panel of a tube belt or pocket belt. The core idea of these approaches has been in each case, for elastic rubber or plastic-material strips connected to the conveyor belt to be fitted transversely to the longitudinal direction of the conveyor belt and to be offset at certain intervals from one another in the longitudinal direction. It is possible here for the transverse strips to span both the entire belt width and just part of the belt width. It can be established from these documents that the transverse strips may be configured both in a continuous state, in the form of ribs or wave-like strips, and in a divided state, for example, at right angles, in sawtooth form or in trapezoidal form. The divided transverse strips here are configured such that, when the tube belt or pocket belt is deformed in tube or pocket form, the flanks of the strip butt more or less against one another or overlap and thus form partition walls spaced apart in the longitudinal direction. Depending on the height, that is, radial formation, of the transverse strips, the conveyable material is retained in a force-fitting and form-fitting manner during transportation, and it is therefore possible to prevent the conveyable material from sliding back in the conveyor belt and thus to realize relatively large gradients. In the case of the transverse strips being virtually closed, it is even possible to realize vertical conveying directions, wherein purely form-fitting force transmission takes place.
It is a disadvantage of the above-described tube belts or pocket belts that they involve very high outlay, and are therefore expensive to produce. It is thus necessary for the transverse strips, on account of their size, in particular their radial extent, to be produced in the form of separate elements and to be applied subsequently to the conveyor belt for example by means of adhesive bonding, that is, by cold vulcanization. This requires the further operating steps of the transverse strips being separately produced and subsequently installed on the conveyor belt. Single-piece production of conveyor belts with transverse strips, that is, simultaneously with the vulcanization of the conveyor belt, is ruled out in production terms on account of the size of the transverse strips. It may also be necessary for the transverse strips to be installed on the conveyor belt for the first time at the site of use of the conveyor belt, so that there is no increase in the volume of the conveyor belt for transportation purposes. Furthermore, the adhesive-bonding locations constitute a weak point which, over time, will fail sooner than other constituent parts of the conveyor belt.
It is also disadvantageous that, if the known tube belts or pocket belts are suitable for relatively large angles of inclination, that is, above 35° in gradient, the conveyable material is retained in a form-fitting manner by the transverse strips and the latter are subjected to corresponding loading. This requires a corresponding stable and radial formation of the transverse strips with higher material and production costs than in the case of flatter profilings, although the latter do not allow such gradients. It is also the case that the higher transverse strips increase the transportation costs of the conveyor belts, because the latter cannot be wound as tightly for transportation purposes, that is, less belt length per rolled together belt drum can be transported in one journey. At the same time, this means that the pieces of belt which can be transported per drum in one journey are shorter, and there is therefore an increase in the outlay for installing the endlessly closed conveyor belts in the conveyor-belt system. As is also the case with conventional tube belts, the pocket conveyor belts have a smooth surface, as a result of which it is possible to realize the angles of inclination of up to 35°, depending on the bulk-material properties.