Abstract: An apparatus for mixing granular inert material with a resin binder in order to form, on a rotating cylindrical mandrel, a tubular manufactured article composed of an inner layer which adheres to the surface of the mandrel, an outer layer and an intermediate layer constituted by a uniform agglomerate obtained from an amalgamation of the granular inert material with the resin binder, comprising at least one mixing line composed of a feeder which is connected to a duct for feeding the granular inert material and a discharge outlet, a mixing device which has an intake port which is suitable to receive the granular inert material from the discharge outlet of the feeder and connections for feeding the resin binder in the mixing device, the mixing device being suitable to form the uniform agglomerate and to apply it onto the inner layer so as to form the intermediate layer.

Abstract: A mandrel for providing a tubular article, comprising a supporting structure for the sliding guiding of a side wall constituted by a plurality of plate-shaped elements which can move according to a rule of motion which provides for a forward stroke and a return stroke. The elements are guided in a translational motion by members for the coupling and guiding of the elements with respect to the supporting structure. The mandrel comprises a plurality of actuators which are functionally associated with the plate-shaped elements for the controlled translational motion, along the guided path, of the plate-shaped elements according to presettable rules of motion.