Fuente: WIPO "tomato" It is described a device (17) for directing a heated air flow towards a first lateral portion (4A) of a web (4) of packaging material, the device (17) with a distribution housing (30) provided with a first inlet opening (31) for receiving the heated air flow; and a diffusion housing (42) in fluidic communication with the distribution housing (30) and comprising a first wall (43) provided with a number of first through openings (44), wherein the openings (44) are configured for directing, in use, the heated air flow towards the first lateral portion (4A); wherein the distribution housing (30) is integrated with the diffusion housing (42).