Air injector (10) for milking plants comprising a lower body (11) having an air inlet opening (12) for inletting air into the milking plant； a membrane (14) supportedly mounted on the air inlet opening (12)； a tight-sealed lower chamber (25) inferiorly delimited by the membrane (14) and superiorly delimited by an upper body (15)； a coil (23) housed in the upper body (15) and comprising a mobile core (24) and a coil hole (26) connected to the outside； a tight- sealed upper chamber (35) which is formed in the upper body (15), is superiorly delimited by the coil (23) and is connected to the outside through the coil hole (26), wherein the upper body (15) comprises a first hole (29) communicating the upper chamber (35) with a vacuum duct (36) connected to a vacuum pipe of the milking plant, and wherein the upper body (15) comprises a second hole (30) formed in the upper chamber (35), wherein said second hole (30) leads into an annular connecting chamber (31) connected to the lower chamber (25), said mobile core being adapted to move from a rest position, in which it closes the first hole (29) and opens the coil hole (26), to a position in which the mobile core (24) is lifted and opens the first hole (29) while closing the coil hole (26), so as to let air flow into or create vacuum in the upper chamber (35) and in the lower chamber (25) connected thereto in order to generate a movement of the membrane (14).L'invention concerne un injecteur d'air (10) pour des installations de traite, comprenant un corps inférieur (11) comportant une ouverture d'entrée d'air (12) pour introduire de l'air dans l'installation de traite； une membrane (14) est montée en appui sur l'ouverture d'entrée d'air (12)； une chambre inférieure hermétique (25) délimitée dans la partie inférieure par la membrane (14) et délimitée dans la partie supérieure par un corps supérieur (15)； une bobine (23) logée dans le corps supérieur (15) et comprenant un noyau mobile (24) et un trou de bobine (26) reliés à l
