Abstract: A flexible belt, made of an elastomeric material, comprising an annular body, delimited by two base surfaces and by two lateral sides; at least one of the base surfaces disposed with a predetermined winding arc around a pulley from which it receives or, to which it transmits, motion by friction. The sides of the annular body are inactive for transmitting the forces by friction. The belt that is for example, flat, is extensible, and it comprises at least one group of three layers in direct contact with one another, each layer of which includes or comprises reinforcing fibers disposed in a single predetermined direction. In the reinforcing structure no inextensible cords are present. The belt may comprise an annular element on at least one of the base surfaces of the annular body, for opposing any lateral shifting relative to the transmission pulley.

Abstract: A V-belt (1) comprising at least three layers (2, 3, 4) of elastomeric material embedding discontinuous fibers (5, 6, 7); one of the layers (2) comprises fibers (5) directed transversally to the belt longitudinal direction and the two remaining layers (3, 4) comprise fibers (6, 7) mutually inclined in opposite direction with respect to the belt longitudinal direction X--X, the layers in which the fibers are inclined in the belt longitudinal direction having an equal extensibility. The three layers are in direct mutual contact and the belt is devoid of inextensible longitudinal reinforcement strands or the like. In some embodiments, the belt may be part of a two-pulley transmission, in particular for stepless speed change gears, where only one pulley is of the expanding type.

Abstract: A power transmission belt which is substantially V-shaped in cross-section has insert members which are resistant to transverse compression embedded in an elastomeric or plastomeric body. Protective layers of elastomer or plastomer having oriented fibers dispersed therein cover the flanks of the belt and, if necessary, are disposed in addition to the belt body adjacent to a base of the belt.