The spray gun is subdivided into a first body (4), in ternally of which a cavity (6) is afforded, and a second body (5) which is perpendicular to the first body (4) and internally afforded a through hole (25) communicating with the cavity (6). An obturator (14) is present internally of the cavity (6), on which obturator (14) elastic means (21) act. Means for activating (26) are located internally of the through hole (25), which activate the obturator (14) and open into the cavity (6) and are in contact with the obturator (14).