Abstract: A rotor (1) of a machine for spraying concrete, mortar or a refractory lining material comprises conveying chambers (11') arranged concentrically around its axis, and delimited by cylindrical walls (11) of a porous, air-permeable material, the inside of the walls (11) being machined smooth. Each cylindrical wall (11) is surrounded by an air chamber (10), each of which is acted upon, between a charging point (26) and a discharge point (27), by the pressure of a compressed air source (32) so as to produce air flows which pass through the porous walls (11) into the conveying chambers (11'). The material to be conveyed by the conveying chambers (11') between the charging point (26) and the discharge point (27) is at least in the regions close to the wall acted upon by these air flows so as to prevent the material from adhering to the chamber walls (11'). The discharge through the discharge opening (27) into a conveying line (30) takes place essentially by gravity and by the action of an injector nozzle (31).

Abstract: A concrete gun comprising in combination a rotor, a plurality of chambers arranged in said rotor in a circular array and extending parallel to the axis of said rotor, sealing plates of elastomeric material engaging the ends of the rotor and closing said chambers, a vent orifice comprising a recess in one of said sealing plates, said recess being located to be successively in register with said chambers upon rotation of said rotor, an air filter communicating said recess with the surrounding air and a clearing device for the recess including an actuating element extending from the recess to outside the gun. By reason of the external actuating element the vent orifice can be periodically cleaned of deposited residue without danger or having to shut down the machine.