# Conventional Selection of Mechanical Fasteners for Flat Belts
## 1 Introduction
A rubber-fabric belt consists of several layers of rubber and fabric, i.e., spacers  
Figure 1: Structural diagram of a belt conveyor with the use of a mechanical connector. Structural description in the text of the article. Other markings: a—angle of contact the roller by the conveyor belt, \(\delta\)—the lower belt deflection angle, which is the same as the angle between the force vectors in the upper and lower conveyor belt, \(S_{1}\)—force in the upper band, \(S_{2}\)—force in the lower band, \(P\)—driving force, \(d\)—diameter of the roller, \(\theta\)—angle of deviation of the vector of the resultant force loading the shaft. (Detail A and Detail B are shown in the following drawings). forming the core of the belt and transmitting mainly longitudinal and transverse tensile forces, running and bearing covers and side edges. Spacers can be made of cotton, cellulose fiber, viscose silk, polyamide (generally polyamide fibers are nylon, perlon, stylon, capron), polyester (generally polyester fibers are diolene, dacron, terylene), aromatic polyamide (Aramid, the name comes from AROMatische PolyAMID), or glass fiber--usually made of cross-weave fabrics. Covers, on the other hand, are most often made of rubber materials based on CR, NBR and PVC polymers in flame-retardant tapes, or SBR or NR/BR in flame retardant tapes. In addition to elastic fabric-rubber belts, you can also find belts made of the so-called TPU, i.e., thermoplastic polyurethane, most often reinforced with aramid. Thermoplastic polyurethane is a thermoplastic elastomer, which is characterized above all by extraordinary flexibility while maintaining high abrasion and weather resistance. It is not damaged by various solvents and lubricants. It exhibits good toughness resistance, good shock, vibration and shock damping properties, which are of great importance in the field of conveyors. This material is also suitable for mixing with other polymers, such as ABS or PMMA. Increasingly often, you can also come across new material solutions for elastic bands. This primarily includes composite belts. Such conveyor belts are widely used in industry for transporting products using negative pressure [1; 10; 11; 12; 13; 14; 15]. The material diversity of the elastic belts themselves indicates the resulting problem of fastening belts. Due to the fact that each conveyor belt has different mechanical properties, the method of connecting them is a very important aspect. Conveyor belts can be connected in three main ways: vulcanized (weldable or heat-weldable), glued or mechanically. The latter are used because of the ease of assembly and the possibility of detaching the ends of the belt, e.g., for cleaning the belt. Mechanical fasteners have different durability, depending on many factors. The reason for the reduction of strength or destruction of the mechanical fastener may be excessive loads, fatigue phenomena of the ends of the joined belts or mechanical elements, abrasive wear of metal elements, corrosion or improper execution of the connection. The strength of mechanical connections of conveyor belts is a complex issue due to the variety of materials (materials and structure of the belt and the metal part of the connection) and the load states in the joints. The aforementioned forces that transmit the elastic bands are related in a specific way to the mechanical connections and their properties, or rather to the load-bearing capacity. The relative strength of the mechanical connection of the belt must be at least 50% of the belt's nominal breaking strength during transport of spoil. The presented connections are especially suitable for elastic fabric-rubber bands without a core made of steel ropes, but also other ones, such as, for example, made of TPU. The connections are designed to be compatible with the standard widths of the manufactured conveyor belts. Based on the literature [16; 17; 18; 19; 20], an initial analysis of the distribution of stresses propagating in the belt conveyor system was performed (Figure 1).