Apparatus for applying viscous mass to a surface, method for cleaning valves thereof and traffic printer based on such apparatus

An applicator (11) for application of a viscous mass (31) to a surface (33) comprising a bottom wall (13) and a heated chamber (32) in communication with bottom wall openings (12) controlled by valves (14) allowing dropwise discharge of the viscous mass to the surface, characterized in that each of the valves (14) are non-packed and comprise an outer sleeve (15) having a smooth internal surface and at least one through opening (16) in a wall of the outer sleeve (15), and a valve plug (17) with a smooth outer surface configured to substantially conform to the internal surface of the outer sleeve (15), the valve plug (17) being arranged to be reciprocated from a closed position completely sealing the at least one through opening (16) in the wall of the outer sleeve (15), to an elevated open position in which at least the lowermost part of the at least one through opening (16) is uncovered, thereby allowing viscous mass (31) to pass therethrough from the outside of the outer sleeve (15) towards one of the bottom wall openings (12).